温度变送器毕业设计外文翻译
SITRANS T 温度变送器
外壳背后是连接电源的电气接头，采用的是 4~20mm 环路供电。此接 头做成符合 EN 175301-803A 标准的插头形式。
外壳前边是一个 5 位的显示器，并外罩玻璃窗。显示屏下边是用于设 置 SITRANS TF2 参数的 3 个按键。显示屏上方是指示操作状态的绿色 和红色 LED。
SITRANS TF2 带tw温o-度wi传re感sy器stem
显示 显示器
SITRANS TF2 具有一个 5 位的显示器，并外罩玻璃窗。显示器显示下 列数据： • 被测温度 • 单位 （°C， °F， oR 或 K 和 mA 或％） • 越限，由 LED 和显示器上的箭头标号指示
设置
SITRANS TF2 由位于玻璃窗后，显示屏下的 3 个输入按键来设置。
4~20mA，两线制 最小 3.6mA 最大 2mA 极性翻转、过压和短路保护 （UH － 12V） / 0.023A 温度－线性
< ± [ 0.45°C ＋ 0.2％满刻度值 ( 单位 °C)+1 位数字 ( 单位 °C) ] ≤ 100ms < ± 0.15％/10 K < ± 0.01％满刻度值 / V < ± 0.05％/g，各个方向 500Hz （符合 IEC 68-2-64）
/M16x1.5 • 径向形式 （A 类）与保护管平行 /1/2" NPT • 轴向形式 （B 类）与保护管保持一定角度
/1/2" NPT
过程连接 • 连接杆 G1/2B • 连接杆 1/2" - 14NPT • 不同的设计 （请与西门子联系）
加订货代码和简要文字说明： ...
Rosemount
产品数据表00813-0106-4021, Rev TB2022 年 5 月Rosemount™ 3144P 温度变送器采用 Rosemount X-well™技术每一份责任都意味着无数挑战。
温度测量不准确或不可用会导致意外停工和产品不符合规格，生产和质量目标定的再高也没用。
温度测量不不可信就可能需要人工反复巡视；因此需要担心维护人员的安全，而且还导致生产停滞损失。
此外，如果缺乏改善合规性的信息或工具，很难提高安全性、达到政府法规和公司规范的标准。
很多公司把目光转向艾默生，他们深知自己需要可靠地测量温度并随时了解温度测量结果，才能应对这些挑战并实现自己的业务目标。
通过 Rosemount 3144P 变送器，您可以更好地观察温度过程，从而提高安全性、符合法规、对有限资源进行最佳利用并达到您的生产和质量目标。
利用 Rosemount X-well 技术、高级诊断功能以及卓越的变送器可靠性和精度，您可以最大限度地降低不符合规格的产品数量，减少维护和停工，提高有限资源的使用率，并符合法规要求。
功能与优点Complete Point Solution ™准确测量监测应用中的过程温度，无需热套管或过程穿孔■简化温度测量点的规格参数、安装和维护，并消除潜在的泄漏点。
■通过变送器内置的热传导算法计算出可重复且准确的过程温度测量结果。
■测量管道表面和环境温度利用装置和过程管道的热传导性质提供准确的过程测量结果。
使用资产位号随时获取信息新发运设备包含一个唯一的二维码资产位号，您可以通过它直接从设备访问序列化信息。
通过此功能，您可以：■在您的 MyEmerson 账号上访问设备图纸、图表、技术文档和故障排除信息。
■缩短平均维修耗时，提高维护效率。
■确保您定位了正确的设备。
■省去耗时的先定位和抄录铭牌再查看资产信息的工作。
内容功能与优点........................................................................................................................................................................................2订购信息...........................................................................................................................................................................................5如何订购 Rosemount X-well 技术. (12)技术规格.........................................................................................................................................................................................13产品认证.........................................................................................................................................................................................26尺寸图 (35)Rosemount 3144P2022 年 5 月卓越的现场可靠性和创新性的过程测量方案■超高精度和稳定性■支持通用传感器输入（热电阻、热电偶、mV、ohms），可支持单传感器或双传感器装配■广泛的传感器和过程诊断产品■符合 SIL3：公认的第三方机构对在达到 SIL 3 要求（SIL 2 单用 [1oo1] 和 SIL3 冗余使用 [1oo2] 的最低要求）的仪表安全系统中的使用进行了 IEC61508 认证■双室外壳■大 LCD 显示屏■4–20 mA HART®，可选择版本（5 和 7）■F OUNDATION™现场总线，符合 ITK 6.0 和 NE107标准凭借一流的产品技术规格和功能提高效率■精度和稳定性业界领先，能够减少维护工作，提高性能。
E+H 温度变送器 (Endress+Hauser) 温度变送器
1) 设定量程的 %。测量精度 = 数字量测量精度 + 数 / 模 (D/A) 转换精度 2) 仅适用于带 “ 高级电子模块 ” 的仪表
电阻 (Ω) 电压 (mV)
测量范围
10...400 Ω 10...2000 Ω -20...100 mV
± 0.08 Ω ± 1.6 Ω
± 20 μV
测量精度
数字量
C 型 (W5Re-W26Re) D 型 (W3Re-W25Re)
L 型 (Fe-CuNi) U 型 (Cu-CuNi)
40...+1820 °C (+104...3308 °F) -270...+1000 °C (-454...1832 °F) -210...+1200 °C (-346...2192 °F) -270...+1372 °C (-454...2501 °F) -270...+1300 °C (-454...2372 °F)
Dusen)
-200...850 °C (-328...1562 °F) -200...850 °C (-328...1562 °F)
• 接线方式：两线制、三线制或四线制连接 • 两线制回路，可以进行线缆阻抗补偿 (0...30 Ω) • 三线制和四线制回路，传感器连接电缆的最大阻抗为 50 Ω / 线 • 传感器电流：≤ 0.3 mA
• HART® 通信，通过手操器现场操作仪表，或通过 PC 机远程操作仪表
• 可选：不锈钢外壳，适用于 EEx d 防爆场合
优势
• 通过HART®通信对各种输入信号进行通用型编程 设置
• 背光显示，可旋转 • 通过 PC 操作软件进行可视化操作和维护，例如：
FieldCare 或 ReadWin® 2000 操作软件 • 两线制技术， 4...20 mA 模拟量输出 • 低电压检测 • 整个温度范围内的高精度测量 • 传感器监控：
【精品】温度变送器外文翻译(中英文翻译)
温度变送器外文翻译(中英文翻译)TT302 温度变送器概述TT302温度变送器接收毫伏(mV)输出的信号，这类传感器包括热电偶或阻性传感器，例如：热电阻（RTD）。
它所接受的信号必须在允许的输入范围之内。
允许输入电压范围为-50到500，电阻范围为0到2000欧姆。
功能描述-硬件每个板的功能介绍如下：图2.1 TT302-硬件构成方框图多路转换器多路转换器将变送器端子接到相应信号调理板上，以保证在正确的端子上测量电压。
信号调理板他的作用给输入信号提供一个正确的值以满足A/D转换。
A/D转换器A/D转换器将输入信号转换成数字形式传给CPU。
信号隔离他的作用在输入和CPU之间隔离控制信号和数字信号。
中央处理单元（CPU） RAM PROM和EEPROMCPU是变送器的智能部分，主要完成测量，板的执行，自诊断和通信的管理和运行。
系统程序存储在PROM中。
RAM用于暂时存放运算数据。
在RAM中存放的数据一旦断电立即消失，所以数据必须保存在不易丢失的EEPROM中。
例如：标定，块的标识和组态等数据。
通信控制器监视在线动态，调整通信信号，插入，删除预处理，滤波。
电源变送器电路通过现场总线电源供电。
电源隔离像信号隔离一样，供给输入部分的信号必须要隔离，电源隔离采用变压器将直流供电电源转换成高频交流供电。
显示控制器从CPU接收数据送给LCD显示器的显示部分，此时显示器必须处于打开状态。
本机调整它有两个磁性驱动开关，它们必须由磁性工具来驱动而不是机械或电的接触。
图2.2-LCD指示器温度传感器TT302像前面所描述的那样，可以兼容多种类型的传感器。
TT302为使用热电偶或热电阻RTD 测量温度进行了特殊设计。
此类传感器的基本内容如下所述：热电偶热电偶由两种不同的金属或合金在一端连接在一起所组成的，被称为测量端或热端。
测量端必须放在测量点上，热电偶的另一端是打开的连接在温度变送器上，这一端称做参考端或冷端。
在大多数应用中，塞贝克效应可以充分解释热电偶的工作原理。
数字温度传感器毕业论文中英文资料外文翻译文献[管理资料]
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毕业论文中英文资料外文翻译文献外文资料DS1722 Digital ThermometerWith scientific and technological progress and development of the types of temperature sensors increasingly wide range of application of the increasingly widespread, and the beginning analog toward digital, single-bus, dual-bus and bus-3 direction. And the number of temperature sensors because they apply to all microprocessor interface consisting of automatic temperature control system simulation can be overcome sensor and microprocessor interface need signal conditioning circuit and A / D converters advant ages of the drawbacks, has been widely used in industrial control, electronic transducers, medical equipment and other temperature control system. Among them, which are more representative of a digital temperature sensor DS18B20, MAX6575, the DS1722, MAX6636 other. This paper introduces the DS1722 digital temperature sensor characteristics, the use of the method and its timing. Internal structure and other relevant content.FEATURES:Temperature measurements require no external components;Measures temperatures from -55°C to +120°C. Fahrenheit equivalent is -67°F to +248°F;Thermometer accuracy is ±°C;Thermometer resolution is configurable from 8 to 12 bits (°C to °C resolution);Data is read from/written to via a Motorola Serial Peripheral Interface (SPI) or standard 3-wire serial interface;Wide analog power supply range ( - );Separate digital supply allows for logic;Available in an 8-pin SOIC (150 mil), 8-pin USOP, and flip chip package;PIN ASSIGNMENTFIGURE 1 PIN ASSIGNMENTPIN DESCRIPTION:SERMODE - Serial Interface Mode.CE - Chip Enable.SCLK - Serial Clock.GND – Ground.VDDA - Analog Supply Voltage.SDO - Serial Data Out.SDI - Serial Data In.VDDD - Digital Supply Voltage.DESCRIPTION:The DS1722 Digital Thermometer and Thermostat with SPI/3-Wire Interface provides temperature readings which indicate the temperature of the device. No additional components are required; the device is truly a temperature-to-digital converter. Temperature readings are communicated from the DS1722 over a Motorola SPI interface or a standard 3-wire serial interface. The choice of interface standard is selectable by the user. For applications that require greater temperature resolution, the user can adjust the readout resolution from 8 to 12 bits. This is particularly useful in applications where thermal runaway conditions must be detected quickly.For application flexibility, the DS1722 features a wide analog supply rail of - . A separate digital supply allows a range of to . The DS1722 is available in an 8-pin SOIC (150-mil), 8-pin USOP, and flip chip package.Applications for the DS1722 include personal computers/servers/workstations, cellular telephones, office equipment, or any thermally-sensitive system.OVERVIEW:A block diagram of the DS1722 is shown in Figure 2. The DS1722 consists offour major components:1. Precision temperature sensor.2. Analog-to-digital converter.3. SPI/3-wire interface electronics.4. Data registers.The factory-calibrated temperature sensor requires no external components. The DS1722 is in a power conserving shutdown state upon power-up. After power-up, the user may alter the configuration register to place the device in a continuous temperature conversion mode or in a one-shot conversion mode. In the continuous conversion mode, the DS1722 continuously converts the temperature and stores the result in the temperature register. As conversions are performed in the background, reading the temperature register does not affect the conversion in progress. In the one-shot temperature conversion mode, the DS1722 will perform one temperature conversion, store the result in the temperature register, and then eturn to the shutdown state. This conversion mode is ideal for power sensitive applications. More information on the configuration register is contained in the “OPERATION-Programming”section. The temperature conversion results will have a default resolution of 9 bits. In applications where small incremental temperature changes are critical, the user can change the conversion resolution from 9 bits to 8, 10, 11, or 12. This is accomplished by programming the configuration register. Each additional bit of resolution approximately doubles the conversion time. The DS1722 can communicate using either a Motorola Serial Peripheral Interface (SPI) or standard 3-wire interface. The user can select either communication standard through the SERMODE pin, tying it to VDDD for SPI and to ground for 3-wire. The device contains both an analog supply voltage and a digital supply voltage (VDDA and VDDD, respectively). The analog supply powers the device for operation while the digital supply provides the top rails for the digital inputs and outputs. The DS1722 was designed to be Logic-Ready.DS1722 FUNCTIONAL BLOCK DIAGRAM Figure 2OPERATION-Measuring Temperature:The core of DS1722 functionality is its direct-to-digital temperature sensor. The DS1722 measures temperature through the use of an on-chip temperature measurement technique with an operating range from -55°to +120°C. The device powers up in a power-conserving shutdown mode. After power-up, the DS1722 may be placed in a continuous conversion mode or in a one-shot conversion mode. In the continuous conversion mode, the device continuously computes the temperature and stores the most recent result in the temperature register at addresses 01h (LSB) and 02h (MSB). In the one-shot conversion mode, the DS1722 performs one temperature conversion and then returns to the shutdown mode, storing temperature in the temperature register. Details on how to change the setting after power up are contained in the “OPERATION-Programming”section. The resolution of the temperature conversion is configurable (8, 9, 10, 11, or 12 bits), with 9-bit readings the default state. This equates to a temperature resolution of °C, °C, °C, °C, or °C. Following each conversion, thermal data is stored in the thermometer register in two’s complement format; the information can be retrieved over the SPI or 3-wire interface with the address set to the temperature register, 01h (LSB) and then 02h (MSB). Table 2 describesthe exact relationship of output data to measured temperature. The table assumes the DS1722 is configured for 12-bit resolution; if the evince is configured in a lower resolution mode, those bits will contain 0s. The data is transmitted serially over the digital interface, MSB first for SPI communication and LSB first for 3-wire communication. The MSB of the temperature register contains the “sign” (S) bit, denoting whether the temperature is positive or negative. For Fahrenheit usage, a lookup table or conversion routine must be used.AddressLocation S 2625242322212002h MSB (unit = ℃) LSB2-12-22-32-40 0 0 0 01hTEMPERATURE DIGITAL OUTPUT(BINARY) DIGITAL OUTPUT(HEX)+120℃0111 1000 0000 0000 7800h+ 0001 1001 0001 0000 1910h+ 0000 1010 0010 0000 0a20h+ 0000 0000 1000 0000 0080h0 0000 0000 0000 0000 0000h1111 1111 1000 0000 Ff80h1111 0101 1110 0000 F5e0h1110 0110 1111 0000 E6f0h-55 1100 1001 0000 0000 C900h OPERATION-Programming:The area of interest in programming the DS1722 is the Configuration register. All programming is done via the SPI or 3-wire communication interface by selecting the appropriate address of the desired register location. Table 3 illustrates the addresses for the two registers (configuration and temperature) of the DS1722.Register Address Structure Table 3CONFIGURATION REGISTER PROGRAMMING:The configuration register is accessed in the DS1722 with the 00h address for reads and the 80h address for writes. Data is read from or written to the configuration register MSB first for SPI communication and LSB first for 3-wire communication. The format of the register is illustrated in Figure 2. The effect each bit has on DS1722 functionality is described below along with the power-up state of the bit. The entire register is volatile, and thus it will power-up in the default state.CONFIGURATION/STATUS REGISTER Figure 21SHOT = One-shot temperature conversion bit. If the SD bit is "1", (continuous temperature conversions are not taking place), a "1" written to the 1SHOT bit will cause the DS1722 to perform one temperature conversion and store the results in the temperature register at addresses 01h (LSB) and 02h (MSB). The bit will clear itself to "0" upon completion of the temperature conversion. The user has read/write access to the 1SHOT bit, although writes to this bit will be ignored if the SD bit is a "0", (continuous conversion mode). The power-up default of the one-shot bit is "0".R0, R1, R2 = Thermometer resolution bits. Table 4 below defines the resolution of the digital thermometer, based on the settings of these 3 bits. There is a direct tradeoff between resolution and conversion time, as depicted in the AC Electrical Characteristics. The user has read/write access to the R2, R1 and R0 bits and the power-up default state is R2="0", R1="0", and R0="1" (9-bit conversions).THERMOMETER RESOLUTION CONFIGURATION Table 4SD = Shutdown bit. If SD is "0", the DS1722 will continuously perform temperature conversions and store the last completed result in the temperature register. If SD is changed to a "1", the conversion in progress will be completed and stored and then the device will revert to a low-power shutdown mode. The communication port remains active. The user has read/write access to the SD bit and the power-up default is "1" (shutdown mode).SERIAL INTERFACE:The DS1722 offers the flexibility to choose between two serial interface modes. The DS1722 can communicate with the SPI interface or with a standard 3-wire interface. The interface method used is determined by the SERMODE pin. When this pin is connected to VDDD SPI communication is selected. When this pin is connected to ground, standard 3-wire communication is selected.SERIAL PERIPHERAL INTERFACE (SPI):The serial peripheral interface (SPI) is a synchronous bus for address and data transfer. The SPI mode of serial communication is selected by tying the SERMODE pin to VDDD. Four pins are used for the SPI. The four pins are the SDO (Serial Data Out), SDI (Serial Data In), CE (Chip Enable), and SCLK (Serial Clock). The DS1722 is the slave device in an SPI application, with the microcontroller being the master. The SDI and SDO pins are the serial data input and output pins for the DS1722, respectively. The CE input is used to initiate and terminate a data transfer. The SCLK pin is used to synchronize data movement between the master (microcontroller) and the slave (DS1722) devices. The shift clock (SCLK), which is generated by the microcontroller, is active only when CE is high and during address and data transfer to any device on the SPI bus. The inactive clock polarity is programmable in somemicrocontrollers. The DS1722 offers an important feature in that the level of the inactive clock is determined by sampling SCLK when CE becomes active. Therefore, either SCLK polarity can be accommodated. There is one clock for each bit transferred. Address and data bits are transferred in groups of eight, MSB first.3-WIRE SERIAL DATA BUS:The 3-wire communication mode operates similar to the SPI mode. However, in 3-wire mode, there is one bi-directional I/O instead of separate data in and data out signals. The 3-wire consists of the I/O (SDI and SDO pins tied together), CE, and SCLK pins. In 3-wire mode, each byte is shifted in LSB first unlike SPI mode where each byte is shifted in MSB first. As is the case with the SPI mode, an address byte is written to the device followed by a single data byte or multiple data bytes.外文资料译文DS1722数字温度传感器随着科学技术的不断进步和发展，温度传感器的种类日益繁多，应用逐渐广泛，并且开始由模拟式向着数字式、单总线式、双总线式和三总线式发展。
电气工程与自动化专业外文翻译--(中英文对照)温度控制简介和PID控制器--
电气工程与自动化专业外文翻译--(中英文对照)温度控制简介和PID控制器--河北建筑工程学院毕业设计(论文)外文资料翻译系别: 电气工程系专业: 电气工程及其自动化班级:姓名:学号:外文出处: Specialized English For ArchitecturalElectric Engineering and Automation附件:1、外文原文;2、外文资料翻译译文。
指导教师评语:签字:年月日注:请将该封面与附件装订成册。
1、外文原文Introductions to temperature controland PID controllersProcess control system.Automatic process control is concerned with maintaining process variables temperatures pressures flows compositions, and the like at some desired operation value. Processes are dynamic in nature. Changesare always occurring, and if actions are not taken, the important process variables-those related to safety, product quality, and production rates-will not achieve design conditions.In order to fix ideas, let us consider a heat exchanger in which a process stream is heated by condensing steam. The process is sketched in Fig.1Fig. 1 Heat exchangerThe purpose of this unit is to heat the process fluid from someinlet temperature, Ti(t), up to a certain desired outlet temperature,T(t). As mentioned, the heating medium is condensing steam.The energy gained by the process fluid is equal to the heat released by the steam, provided there are no heat losses to surroundings, iiithat is, the heat exchanger and piping are well insulated.In this process there are many variables that can change, causingthe outlet temperature to deviate from its desired value. [21 If this happens, some action must be taken to correct for this deviation. Thatis, the objective is to control the outlet process temperature tomaintain its desired value.One way to accomplish this objective is by first measuring the temperature T(t) , then comparing it to its desired value, and, based on this comparison, deciding what to do to correct for any deviation. The flow of steam can be used to correct for the deviation. This is, if the temperature is above its desired value, then the steam valve can be throttled back to cut the stearr flow (energy) to the heat exchanger. If the temperature is below its desired value, then the steam valve couldbe opened some more to increase the steam flow (energy) to the exchanger. All of these can be done manually by the operator, and since the procedure is fairly straightforward, it should present no problem. However, since in most process plants there are hundreds of variablesthat must be maintained at some desired value, this correction procedure would required a tremendous number of operators. Consequently, we would like to accomplish this control automatically. That is, we want to have instnnnents that control the variables wJtbom requ)ring interventionfrom the operator. (si This is what we mean by automatic process control.To accomplish ~his objective a control system must be designed and implemented. A possible control system and its basic components areshown in Fig.2.Fig. 2 Heat exchanger control loopThe first thing to do is to measure the outlet temperaVare of the process stream. A sensor (thermocouple, thermistors, etc) does this. This sensor is connected physically to a transmitter, which takes the output from the sensor and converts it to a signal strong enough to be transmitter to a controller. The controller then receives the signal, which is related to the temperature, and compares it with desired value. Depending on this comparison, the controller decides what to do to maintain the temperature at its desired value. Base on this decision, the controller then sends another signal to final control element, which in turn manipulates the steam flow.The preceding paragraph presents the four basic components of all control systems. They are(1) sensor, also often called the primary element.(2) transmitter, also called the secondary element.(3) controller, the "brain" of the control system.(4) final control system, often a control valve but not always.Other common final control elements are variable speed pumps, conveyors, and electric motors.The importance of these components is that they perform the three basic operations that must be present in every control system. These operations are(1) Measurement (M) : Measuring the variable to be controlled is usually done by the combination of sensor and transmitter.(2) Decision (D): Based on the measurement, the controller must then decide what to do to maintain the variable at its desired value.(3) Action (A): As a result of the controller's decision, the system must then take an action. This is usually accomplished by the final control element.As mentioned, these three operations, M, D, and A, must be present in every control system.PID controllers can be stand-alone controllers (also called single loop controllers), controllers in PLCs, embedded controllers, or software in Visual Basic or C# computer programs.PID controllers are process controllers with the following characteristics:Continuous process controlAnalog input (also known as "measuremem" or "Process Variable" or "PV")Analog output (referred to simply as "output")Setpoint (SP)Proportional (P), Integral (I), and/or Derivative (D) constantsExamples of "continuous process control" are temperature, pressure, flow, and level control. For example, controlling the heating of a tank. For simple control, you have two temperature limit sensors (one low and one high) and then switch the heater on when the low temperature limit sensor tums on and then mm the heater off when the temperature rises to the high temperature limit sensor. This is similar to most home air conditioning & heating thermostats.In contrast, the PID controller would receive input as the actual temperature and control a valve that regulates the flow of gas to the heater. The PID controller automatically finds the correct (constant) flow of gas to the heater that keeps the temperature steady at the setpoint. Instead of the temperature bouncing back and forth between two points, the temperature is held steady. If the setpoint is lowered, then the PID controller automatically reduces the amount of gas flowing to the heater. If the setpoint is raised, then the PID controller automatically increases the amount of gas flowing to the heater. Likewise the PID controller would automatically for hot, sunny days (when it is hotter outside the heater) and for cold, cloudy days.The analog input (measurement) is called the "process variable" or "PV". You want the PV to be a highly accurate indication of the process parameter you are trying to control. For example, if you want to maintain a temperature of + or -- one degree then we typically strivefor at least ten times that or one-tenth of a degree. If the analog input is a 12 bit analog input and the temperature range for the sensoris 0 to 400 degrees then our "theoretical" accuracy is calculated to be 400 degrees divided by 4,096 (12 bits) =0.09765625 degrees. [~] We say "theoretical" because it would assume there was no noise and error in our temperature sensor, wiring, and analog converter. There are other assumptions such as linearity, etc.. The point being--with 1/10 of a degree "theoretical" accuracy--even with the usual amount of noise and other problems-- one degree of accuracy should easily be attainable.The analog output is often simply referred to as "output". Oftenthis is given as 0~100 percent. In this heating example, it would mean the valve is totally closed (0%) or totally open (100%).The setpoint (SP) is simply--what process value do you want. In this example--what temperature do you want the process at?The PID controller's job is to maintain the output at a level sothat there is no difference (error) between the process variable (PV) and the setpoint (SP).In Fig. 3, the valve could be controlling the gas going to a heater, the chilling of a cooler, the pressure in a pipe, the flow through a pipe, the level in a tank, or any other process control system. What the PID controller is looking at is the difference (or "error") between the PV and the SP.SETPOINT P，I，&DCONSTANTSDifference error PID controlalgorithmprocess outputvariableFig .3 PIDcontrolIt looks at the absolute error and the rate of change of error. Absolute error means--is there a big difference in the PV and SP or a little difference? Rate of change of error means--is the difference between the PV or SP getting smaller or larger as time goes on.When there is a "process upset", meaning, when the process variableor the setpoint quickly changes--the PID controller has to quickly change the output to get the process variable back equal to the setpoint. If you have a walk-in cooler with a PID controller and someone opens the door and walks in, the temperature (process variable) could rise very quickly. Therefore the PID controller has to increase the cooling (output) to compensate for this rise in temperature.Once the PID controller has the process variable equal to the setpoint,a good PID controller will not vary the output. You want the outputto be very steady (not changing) . If the valve (motor, or other control element) is constantly changing, instead of maintaining a constant value, this could cause more wear on the control element.So there are these two contradictory goals. Fast response (fast change in output) when there is a "process upset", but slow response (steady output) when the PV is close to the setpoint.Note that the output often goes past (over shoots) the steady-state output to get the process back to the setpoint. For example, a cooler may normally have its cooling valve open 34% to maintain zero degrees (after the cooler has been closed up and the temperature settled down). If someone opens the cooler, walks in, walks around to find something, then walks back out, and then closes the cooler door--the PID controller is freaking out because the temperature may have raised 20 degrees! Soit may crank the cooling valve open to 50, 75, or even 100 percent--to hurry up and cool the cooler back down--before slowly closing the cooling valve back down to 34 percent.Let's think about how to design a PID controller.We focus on the difference (error) between the process variable (PV) and the setpoint (SP). There are three ways we can view the error. The absolute errorThis means how big is the difference between the PV and SP. If there is a small difference between the PV and the SP--then let's make a small change in the output. If there is a large difference in the PV and SP--then let's make a large change in the output. Absolute error is the "proportional" (P) component of the PID controller.The sum of errors over timeGive us a minute and we will show why simply looking at the absolute error (proportional) only is a problem. The sum of errors over time is important and is called the "integral" (I) component of the PID controller. Every time we run the PID algorithm we add the latest errorto the sum of errors. In other words Sum of Errors = Error 1 q- Error2 + Error3 + Error4 + ....The dead timeDead time refers to the delay between making a change in the output and seeing the change reflected in the PV. The classical example is getting your oven at the right temperature. When you first mm on the heat, it takes a while for the oven to "heat up". This is the dead time. If you set an initial temperature, wait for the oven to reach theinitial temperature, and then you determine that you set the wrong temperature--then it will take a while for the oven to reach the new temperature setpoint. This is also referred to as the "derivative" (D) component of the PID controller. This holds some future changes back because the changes in the output have been made but are not reflectedin the process variable yet. Absolute Error/Proportional One of the first ideas people usually have about designing an automatic process controller is what we call "proportional". Meaning, if the difference between the PV and SP is small--then let's make a small correction to the output. If the difference between the PV and SP is large-- then let's make a larger correction to the output. This idea certainly makes sense.We simulated a proportional only controller in Microsoft Excel.Fig.4 is the chart showing the results of the first simulation (DEADTIME = 0, proportional only):Proportional and Integral ControllersThe integral portion of the PID controller accounts for the offset problem in a proportional only controller. We have another Excel spreadsheet that simulates a PID controller with proportional and integral control. Here (Fig. 5) is a chart of the first simulation with proportional and integral (DEADTIME :0, proportional = 0.4).As you can tell, the PI controller is much better than just the P controller. However, dead time of zero (as shown in the graph) is not common.Fig .4 The simulation chartDerivative ControlDerivative control takes into consideration that if you change the output, then it takes tim for that change to be reflected in the input (PV).For example, let's take heating of the oven.Fig.5The simulation chartIf we start turning up the gas flow, it will take time for the heat to be produced, the heat to flow around the oven, and for the temperature sensor to detect the increased heat. Derivative control sort of "holds back" the PID controller because some increase in temperature will occur without needing to increase the output further. Setting the derivative constant correctly allows you to become more aggressive with the P & I constants.2、外文资料翻译译文温度控制简介和PID控制器过程控制系统自动过程控制系统是指将被控量为温度、压力、流量、成份等类型的过程变量保持在理想的运行值的系统。
外文翻译--基于51单片机温度报警器的设计(适用于毕业论文外文翻译+中英文对照)
外文翻译--基于51单片机温度报警器的设计(适用于毕业论文外文翻译+中英文对照)XXX: Design of a Temperature Alarm Based on 51 MCUDepartment: n EngineeringMajor: Measurement and Control Technology and nClass:Student ID:Name:Supervisor:Date:A microcontroller。
also known as a single-chip computer system。
XXX its ns being integrated on a small chip。
it has most of the components needed for a complete computer system。
such as CPU。
memory。
internal and external bus systems。
and mostof them also have external storage。
At the same time。
it integrates XXX interfaces。
timers。
real-time clocks。
etc。
The most XXX integrate sound。
image。
ork。
and complex input-output systems on a single chip.XXX used in the industrial control field。
Microcontrollers XXX CPUs inside the chip。
The original design concept was to integrate a large number of peripheral devices and CPUs on a chip to make the computer system XXX's Z80 was the first processor designed according to this concept。
SITRANS TH100 温度变送器
避免与大型电气系统太近或使用屏蔽电缆。
两线制 （可设定线路电阻）
三线制 1）
四线制
电源连接(Uaux)
在三线制中，5 号端子没有任何功能同时不能连接。当使用四线制中的 RTD 时，如果选
择了三线制，不用的第四个传感器电缆的电线应该用绝缘胶带电气隔离。
图 8 Pt100 电阻温度计接线板和供电
5.2 在危险区域连接
电源供给必须保证无论是在正常操作情况下或发生系统或部件故障的情况下都没有危险的电压 可以接触到设备。 2.4 合格的人员
“合格的人员”指的是那些熟悉安装，装备，调试和操作产品的人员。他们的行为必须有以 下的资格： ·依照电路安全规则，高压和腐蚀性介质，应具有操作和维护设备/系统的培训或指导/授权。 ·依照安全规则，应具备维护和使用适当的安全设备的培训和指导。 ·对于有爆炸保护的设备：应具备有执行危险系统电路工作的培训或指导/授权。 ·急救培训。
SITRANS TH100 A5E00331168--01
1 介绍
1.1 文件的用途
这个设计手册包括了试车和使用变送器时所需的所有信息。
这个手册针对机械安装设备、电气连接设备、参数设置的人员，以及维修和维护的工程师。
1.2 文档历史
文档历史建立了当前的文件和有效的设备固件间的相互关系。
这个版本的文件可用在下列固件中：
西门子
SITRANS TH100 7NG3211--0*N00 06/2006 版本
温度变送器，装在传感器头部
使用说明书
/sitranst
SITRANS TH100 A5E00331168--01
目录
1 介绍 ……………………………………………………………………………………...…….5 1.1 文件的用途……………………………………………………………………………...………5 1.2 文档历史…………………………………………………………………………………..……5 1.3 附加信息…………………………………………………………………………………...……5
变电站毕业设计~外文翻译
山东理工大学毕业设计（外文翻译材料）学院：专业：学生姓名：指导教师：电气与电子工程学院电气工程及其自动化韦柳军孟繁玉Reliability modelling and analysis for SheffieldSubstation 220 kV upgrade projectCaroline Lee Transend, Networks Pty Ltd , TasmaniaDr Sudhir Agarwal,San Diego, California, USAABSTRACTThis paper describes the application of a defensible probabilistic process in reliability evaluation for Sheffield 220 kV Substation redevelopment project. Sheffield Substation is a hub of 220 kV transmission system in the North and North-West regions of Tasmania. It provides connection to West Coast and Mersey Forth hydro power stations and facilitates power transfers from these power stations to major industrial customers in George Town area and retail andindustrial loads in the North and North-West regions of Tasmania. Therefore, it is important that integrity of Sheffield Substation is protected as much as possible and consequences of unplanned outages minimised to prevent possible widespread system disturbances.Together with General Reliability from San Diego,California, Transend undertook the reliability evaluation of four redevelopment options for Sheffield Substation using SUBREL, substation reliability and TRANSREL, transmission system reliability programs.1.INTRODUCTIONTransend, as a Transmission Service Provider and Transmission Network Operator in Tasmania is responsible for providing reliable electricity supply and providing cost effective development solutions- 1 -of the transmission network. Transend has identified a need for a comprehensive and more objective process in justification of development projects from its capital works program. The need to combine customer reliability targets and economics to achieve cost effective development solutions has been long recognised. A hierarchical framework for overall power system reliability evaluation is presented in [1].Different design, planning and operating principles and techniques have been developed in different countries over many decades in an attempt to find balance between reliability targets and economic constraints [2].Following the reliability concept and principles, differentutilities applied different reliability criteria to justify projects from their capital works program. Reliability criteria can be viewed as conditions that should be satisfied by electricity generation, transmission and distribution systems in order to achieve requiredreliability targets. Reliability criteria usually fall into two categories: established numerical target levels of reliability (eg level of expected energy not supplied) and performance test criteria (eg N-1, N-2 incidents that the system has to withstand). An attempt to combine these two categories into one set of reliability criteria is currently underway in Tasmania [3]. The use of reliability criteria from the first category is the core of probabilistic reliability evaluation approach. The second category is a deterministic reliability evaluation approach. The usefulness of deterministic criteria and security standards in justification of projects from capital works program is challenged in [4]. Instead, an approach involving customers in decision making and simulating a realistic system operation and failure is commended. The basic steps suggested in proper reliability evaluations are based on complete understanding of the equipment and system behaviour including:• Understanding the way the equipment and system operate;- 2 -• Identify the situations in which equipment can fail;• Understand consequences of the failures;• Incorporate these events into the reliability model;•Use the available evaluation techniques tocalculate reliability indices and costs.With this understanding of the system behaviour probability theory is then only seen as a tool to transform this understanding into the likely system future behaviour.2. SELECTION OF EVALUATION TECHNIQUE AND SOFTWARE TOOLS There are two main categories of evaluation techniques[5]: analytical (stateenumeration) and Monte Carlo simulation. The advantages and disadvantages of both methods are discussed in [1].Analytical technique was chosen by Transend because of its usefulness in comparing different development options for network development projects. This approach was presented also in the Electricity Supply Association of Australia Guidelines for Reliability Assessment Planning [6]. Consequently, decision was made to acquire SUBREL, and TRANSREL, substation reliability and transmission system reliability programs from General Reliability,USA.2.1. SUBREL - SUBSTATION RELIABILITYPROGRAMSUBREL is a computer program which calculates reliability indices for an electricity utility substation and generating station switchyard [7]. The methodology used to analyse impact of substation generated outages on overall system reliability performances has been described in [8]. The program models the following outage events, including all required subsequent automatic and manual switching operations:1. Forced outage of any substation component:- 3 -• Breaker• Transformer• Bus Section• Disconnector2. Forced outage of an incoming line.3. Forced outage overlapping a maintenance outage for substation equipment or an incoming line.4. Stuck breaker (failure to open when needed to clear the fault). SUBREL calculates the following load point indices:• Frequency of Interruption (per year)• Number of Circuits Interruptions (per year)• Outage Duration (minutes per outage)• Annual Total Outage Duration (minutes per year)• Customer Minutes of Interruption CMI (per year)• Expected Unsupplied Energy (EUE) (kWh per year)• Expected Outage Cost ($ per year)SUBREL also calculates the following substation or totalsystem indices:• SAIFI, System Average Interruption Frequency Index• SAIDI, System Average Interruption Duration Index• CAIDI, Customer Average Interruption Duration Index• ASAI, Average Service Availability Index• EUE, Expected Unsupplied Energy (kWh per year)- 4 -• Expected Outage Cost ($ per year)SUBREL generates a list of substation generated outages that can be used further by TRANSREL to analyse impact on overall system reliability performance.2.2. TRANSREL – TRANSMISSION SYSTEM RELIABILITY PROGRAMTRANSREL uses contingency enumeration of transmission contingencies to evaluate power network reliability. It is designed to aid electric utility system planners for reliability assessment of bulk power systems. The process involves specifying contingencies (outages of transmission lines and station originated outages) and performing load flow analysis to determine system problems such as circuit overloads, low/high bus voltages, bus separation or islanding. Using the probability, frequency and duration of the contingencies evaluated, indices of system problems as measures of system unreliability are calculated. Both post contingency and post remedial action indices can be calculated. If no remedial actions are taken to alleviate a problem, the post contingency indices may provide a pessimistic assessment of system reliability. If remedial actions such as generation redispatch, switching of facilities, curtailment of load alleviates some of the system problems, the post remedial action reliability indices provide a more realistic measure of system performance. The amount of load shedding is used as an indicator of contingency severity or system capability to withstand contingencies. Using probabilities of contingencies, expected load curtailment at buses can be calculated as reliability indices. TRANSREL was used with load flow program, PTI PSS/E to examine the impact of an outage on system performance. The types of failures identified for checking the impact of a contingency on system performance are: Transmission circuit overloads - by comparing flows based on the load flow solution with user- 5 -selected circuit ratings; Bus voltage violations - by checking bus voltages against high and low voltage limits, or maximum allowable voltage deviation from the base case; Load curtailment - by tabulating the amount of load curtailed as a result of system failure;Load flow divergence - by tabulating the bus mismatches above a predefined tolerance. TRANSREL computes reliability indices using a contingency enumeration approach, which involves selection and evaluation of contingencies, classification of each contingency according to specified failure criteria, and computation of reliability indices. Reliability indices include frequency, duration and severity (overloads, voltage violations, load curtailed, and energy curtailed). Both system and bus indices are calculated.3.SUBREL AND TRANSREL APPLICATION FOR SHEFFIELD 220 KV SUBSTATION Sheffield Substation is a hub of 220 kV transmission system in the North and North-West regions of Tasmania. As shown on Figure 1, it provides connections from the West Coast and Mersey Forth hydro power stations to the rest of the system. In addition, it supplies Aurora Energy customers in North and North-West regions and major industrial customers in the George Town area.During winter months, from May to September, the amount of energy supplied through and transferred from Sheffield Substation can reach more than 50% of the energy supplied to the rest of the system as shown in Figure 2.As such, Sheffield Substation has been recognized as a vulnerable point in the Tasmanian power system. The total loss of Sheffield Substation during times of large power transfer from West Coast of Tasmania to the rest of the system could possibly lead to a large system disturbance in Tasmania. With the present Sheffield Substation 220 kV layout, the total loss of Sheffield Substation can be caused by a single element failure.- 6 -3.1. DEVELOPMENT OPTIONS ANALYSEDThe need to redesign the existing substation 220 kV layout has been recognised long time ago. The following three options have been selected for detailed modeling and analysis:Option 1: Triple busbar arrangementOption 2: Full breaker and a half and double breaker arrangement Option 3: Partial breaker and half and double breaker arrangement These options were compared against the existing 220 kV busbar design (Do Nothing option).A brief description of each of these options is as follows:3.1.1. DO NOTHING OPTION- 7 -The “Do nothing option” represents the existing 220 kV busbar arrangement at Sheffield Substation. The existing 220 kV Sheffield Substation has had some major changes since substation commissioning and installation of two autotransformers for the North and North-West regions of Tasmania supply in 1967. The substation 220 kV busbar arrangement is double, strung busbar arrangement with one bus coupler. In normal system configuration main bus coupler A752 is closed, 220 kV“S” by pass bus and second bus coupler S752 are not in service. The schematic diagram of this option is shown below. Total number of circuits connected at Sheffield Substation is 12. Total number of circuit breakers is 14 (12 plus 2 bus couplers). Sheffield Substation is a main supply point to the North-West Region of Tasmania. Total load in the region is around 260 MVA. The fault on bus coupler A752 will result in the loss of both busbar A and B and therefore loss of more than 50% of supply in Tasmania during winter season leading to a blackout in the North-West region.West Coast region will loose synchronism with the rest of the system, experience over frequency and will be islanded. The rest of the system will experience.Under frequency and significant amount of load must be shed to prevent total blackout. In the case of 220 kV busbar A fault at Sheffield Substation, two elements supplying the North-West region which are the Sheffield–Burnie 220 kV line and autotransformer T1, would be lost. During high winter load the remaining autotransformer T2 will be overloaded and tripped on overload conditions. This will lead to total blackout in the North-West region of Tasmania. In the case of 220 kV busbar B fault, two elements supplying George Town which are the Sheffield–George Town No 1 transmission line and Sheffield–Palmerston transmission line will be lost. During high winter loads the remaining Sheffield–George Town No 2 line will tripped on overload.- 8 -This will cause significant change in network impedance with requirement to shed load at major industrial customers at George Town. Consequently, this will produce excessive generation connected at Farrell and Sheffield, which can move the system towards unstable operation and cascade of events with possible blackout in the North and North West regions of Tasmania.3.1.2. OPTION 1-TRIPLE BUSBAR ARRANGEMENTThe schematic diagram of this option is shown below In comparison with “do nothing option” this option proposes to use the spare S752 circuit breaker and upgrade a nd energise “S” bypass bus to full size. The existing 12 circuits will be spread across the three busbars. Only one additional 220 kV circuit breaker is required in this option. The total number of circuit breakers in this option is 15.3.1.3. OPTION 2 - FULL BREAKER AND A HALF AND DOUBLE BREAKER ARRANGEMENT The schematic diagram of this option is shown below. This option includes- 9 -creating double breaker and breaker and half arrangements. Breaker and a half arrangement is proposed between Hydro Tasmania’s C ethana power station and autotransformer T1; and Lemonthyme power station and autotransformer T2. The total number of circuit breakers in this option is 19.3.1.4. OPTION 3 - PARTIAL BREAKER AND A HALF AND DOUBLE BREAKER ARRANGEMENTThe schematic diagram of this option is shown below. The main difference in comparison with option 2 is thatthere is no breaker and half arrangements between Hydro Tasmania’s Cethana power station and autotransformer T1; and Lemonthyme power station and autotransformer T2. The establishment of breaker and a half arrangements between these circuits could have as a consequence increase in connection charges for Hydro Tasmania for middle breakers, which needs to be discussed and agreed with this customer. Total number of circuit breakers in this option is 17.3.2. RESULTSIn this study, the following outages are examined:• n-1 forced outage of a station component including transmission lines and transformers• n-1 maintenance overlapping n-1 forced outages•breaker stuck condition following a fault. For a fault on line, transformer, bus or a breaker, only those breakers will be considered for being in a stuck condition that are supposed to trip to clear the fault. In this case back up protection will clear the fault.Apart from the above outages examined, higher order of outages can also be considered and simulated in the programs, however the probability and frequency of- 10 -their occurrence is quite low. Based on the Transend outage data, it was decided that the above settings should capture most of the credible outage events. The number of events for each of the options is given in the following table. These events are generated by the program to study their impact on substation performance. For each event, the program calculates the probability, frequency and duration. Using the connectivity model, it also computes the amount of loss of load and energy for a load point and for the overall substation. Using a linear flow method it checks if the load can be supplied without violating the ratings of any component. The number of outage events enumerated and examined by the SUBREL program depends on the number of components in a station and the program settings. If more components are added to a station, their exposure to failures also increases. To select an optimal design, a balance between the redundancy provided by adding a component (breaker or a busbar) and the increased exposure should be kept in mind. As seen from the tables above, the number of outage events for options 1,2 and 3 is higher than for the existing configuration since these options have more breakers and buses in their suggested configurations. There is no event that causes the complete loss of load in the area (including Burnie, Sheffield and George Town substations in the model) in any of the options. However there are events in each option that will cause partial loss of load. Option 2 has the lowest number of events causing loss of load while the existing configuration has the highest number of events causing loss of load. Reliability indices computed by SUBREL program for each of the option is given in the table below. These indices are computed using the load Probability Density Function (PDF) as unity. PDF of unity means that the load is same throughout the year. The widely used reliability indices such as SAIFI, SAIDI, CAIDI, ASAI,and EUE are computed by the program.Outage costs are calculated based on calculated expected- 11 -unsupplied energy (EUE) and value of lost load applied to particular customer groups. A comprehensive analysis of value of lost load for different customer groups has been undertaken by Monash University for Victorian utilities [9]. Based on the table above it is clear that option 1 – triple busbar arrangement, has lowest outage costs. Based on the list of substation originated outages generated by SUBREL, TRANSREL program was used to indicated consequences on the overall system performances. The voltage violations were encountered only for option2 in 9 simulation events. There were few contingencies for which solution did not converge. For these contingencies, a potential exists that the system will face major problems including a collapse. The system stress and its response will, of course, depend on the system conditions present at the time outages. There are four events for Option 1 that result in non-convergence of the power flow. The probability of these non-convergence cases for Option 1 is 0.0026 which means that there is a potential that exists that the system may collapse once every 400 years. This is a very low likely event and during this time the system is likely to go through several changes. It should also be noted that in this analysis no remedial actions are included. With remedial actions, operators may be able to avoid such a situation.4. CONCLUSIONSThe implementation and application of a probabilistic based planning for selecting a substation configuration provides quite useful information to an engineer in deciding the best option. The use of both SUBREL and TRANSREL programs for Sheffield Substation study has sufficiently demonstrated that it is important to examine all credible outage scenarios that are not possible to do manually. Quantitative indices computed by these programs provide an objective assessment of various- 12 -options considered. For transmission substations it is important that only SUBREL analysis may not provide the complete information. Without performing a TRANSREL analysis,it is likely that the risk posed by a configuration may not be correctly assessed from the overall system point of view. For the Sheffield Substation the triple busbar arrangement (Option 1) is the cheapest option, easy to implement, and reliability indices for Sheffield Substation are the best in this option. The low probabilities divergent cases can be resolved with appropriate remedial actions in place, including, generation rescheduling, voltage support and load shedding.REFERENCES[1] Billinton, R. and Allan, R.N.,:”Power-system reliability in perspective”, IEE Electronic and Power, pp. 231-236, March 1984.[2] “Power System Reliability Analysis. Application Guide,” CIGRE WG03 of SC 38,Edited by Lesley Kelley-Regnier, 1987.[3] “Transmission Network Security and Planning Criteria-draft”, Office of Tasmanian Energy Regulator, August 2005.[4] Al lan, R.N., and Billinton, R.:”Probabilistic methods applied to electric power systems-are they worth it?”,Power Engineering Journal, pp.121-129, May 1992.[5] Billinton, R. and Allan, R.N.,:” Reliability Evaluation of Power Systems”, Pitmans Books, New Yor k and London, 2nd edition, 1996. [6] “ESAA Guidelines for Reliability Assessment Planning,”, November 1997.[7] “Subrel-Substation Reliability Program User Manual”, General Reliability, San Diego, CA, 2002.- 13 -[8] Agarwal, S.K., and Anderson, P.M..: “Effect o f Station Originated Outages on Bulk Power System Reliability, ”, Cigre Symposium, S 38- 91, Montreal, 1991.[9] Monash University,:” Study of the Value of Lost Load” , Study conducted for the Victorian Power Exchange (VPX) company,Melbourne,2000.- 14 -谢菲尔德变电站220千伏升级项目的可靠性建模与分析创见网络私人有限公司，塔斯马尼亚阿加瓦尔博士，美国加利福尼亚州圣迭戈摘要本文介绍了在可靠性评估中的应用一个可防御概率过程谢菲尔德220千伏变电站重建项目。
一体化温度变送器英文使用说明书
JWBIntegration temperaturetransmitter instructionsv3.0First summarizeJWB Integration temperature transmitter is a noncontact measuring temperature field with instrument ，Usually the related secondary instrument or computer data acquisition system supporting the use of the measurement ，It can accuratelymeasure the temperature of all kinds of medium and objects (used scope 200 ℃ ~ 1600 ℃) working process .The Principle of JWB Integration temperature transmitter is taking an amplifier transmission module into the waterproof or the critical terminal box of fabricated temperature sensor ，and connected with the sensor ， output Standard 4 ~ 20 mA DC (two wire) .This series product were issued by the relevant national standards and regulations related GB JJG related content ， and meet the relevant documents to IEC standard ，then finished by learning advantages of the reference of the same products abroad .It Makes the product more reliable, accurate, very suitable for all kinds of environment of the temperature measurement . Second technology parametersPower: 24 V DC (18 ~ 36 V DC) current output load: 500 Ω quartile (24 V DC) . Output: 4 ~ 20 mA .Precision: B level 0.5% (the module working in 10 ℃ ~ 70 ℃).nge: sighed in the product nameplate output protection: the sensor open, themaximum output of module must be less than 25 mA. Third wiring 、appearanceFourththe basic structure3.1 basic structure: sensor + (connection device + junction box + protection tube) +transmission module.3.2 Length: L = protection tube presidents × insert length (unit: mm, the seal facefollowing). 3.3 the length of the cold end.a. Transmission module working temperature between20 ℃ ~ 75 ℃.It makes t he temperature down between the temperature field and radiation by the cold end length ，Protecting the analog module circuit .b. If the thermocouple adopted , there must be cold end length .c. Protecting terminals and cable .d. The standard length of the cold end is 150 mm ,seeing the cold temperaturemeasurement environment influence situation can be appropriately changed ， For example, below 125 ℃ temperature ，it should be 50 mm length or no cold end ，Higher temperature measurement ，The cold end length must be appropriately extended .Fifth installation5.1 Sensor can be insert into the temperature field center position.5.2 Generally, perpendicular installation is used in high temperature measuring, suchas side outfit will make protection pipe deformation damage, then protect the stent may be need.5.3 A strength tube maybe need in disturbance occasion, sensor is inserted into thepipe from strengthen monitoring site; As requiring the fast response time ,keep parts out .5.4 If the measurement of velocity places (such as pipe), not only the impact of the fluid,but also the damage of eddy should be considered.The structure strength of the tube must be good,and the installation method is also very important, such as flowing down the inclined installation, or in the pipeline turn orthogonal place tomeet insert installation.Related knowledge1,According to JJG national measurement standards, the temperature sensor must be inspected between 3 and 6 months once,and be replaced one year old. 2,Transmission modulemust be inspected and calibrated once between 6and 12 months. (the potentiometer Z [W1] the 4mA, G [W2] the 20 mA) 3,Selecting the product structure model carefully according to the work environment, because it relates the safety and life of product.4,Products which were designed by of the usingparty ,if there were problem of the quality and production party have nothing to do.Beijing Collihigh Sensor Techology Co,.Ltd.Address：8F,Tower C,ke shi builing,Armor 28,xinxi road,Haidian district Beijing China Postal code：100085 Tel:86-10-82671108 Fax:86-10-62533666。
温度传感器毕业论文中英文资料外文翻译文献
中英文翻译英文文献原文Temperature Sensor ICs Simplify DesignsWhen you set out to select a temperature sensor, you are no longer limited to either an analog output or a digital output device. There is now a broad selection of sensor types, one of which should match your system's needs.Until recently, all the temperature sensors on the market provided analog outputs. Thermistors, RTDs, and thermocouples were followed by another analog-output device, the silicon temperature sensor. In most applications, unfortunately, these analog-output devices require a comparator, an ADC, or an amplifier at their output to make them useful.Thus, when higher levels of integration became feasible, temperature sensors with digital interfaces became available. These ICs are sold in a variety of forms, from simple devices that signal when a specific temperature has been exceeded to those that report both remote and local temperatures while providing warnings at programmed temperature settings. The choice now isn't simply between analog-output and digital-output sensors; there is a broad range of sensor types from which to choose.Classes of Temperature SensorsFour temperature-sensor types are illustrated in Figure 1. An ideal analog sensor provides an output voltage that is a perfectly linear function of temperature (A). In the digital I/O class of sensor (B), temperature data in the form of multiple 1s and 0s are passed to the microcontroller, often via a serial bus. Along the same bus, data are sent to the temperature sensor from the microcontroller, usually to set the temperature limit at which the alert pin's digital output will trip. Alert interrupts the microcontroller when the temperature limit has been exceeded. This type of device can also provide fan control.Figure 1. Sensor and IC manufacturers currently offer four classes of temperature sensors."Analog-plus" sensors (C) are available with various types of digital outputs. The V OUT versus temperature curve is for an IC whose digital output switches when a specific temperaturehas been exceeded. In this case, the "plus" added to the analog temperature sensor is nothing more than a comparator and a voltage reference. Other types of "plus" parts ship temperature data in the form of the delay time after the part has been strobed, or in the form of the frequency or the period of a square wave, which will be discussed later.The system monitor (D) is the most complex IC of the four. In addition to the functions provided by the digital I/O type, this type of device commonly monitors the system supply voltages, providing an alarm when voltages rise above or sink below limits set via the I/O bus. Fan monitoring and/or control is sometimes included in this type of IC. In some cases, this class of device is used to determine whether or not a fan is working. More complex versions control the fan as a function of one or more measured temperatures. The system monitor sensor is not discussed here but is briefly mentioned to give a complete picture of the types of temperature sensors available.Analog-Output Temperature SensorsThermistors and silicon temperature sensors are widely used forms of analog-output temperature sensors. Figure 2 clearly shows that when a linear relationship between voltage and temperature is needed, a silicon temperature sensor is a far better choice than a thermistor. Over a narrow temperature range, however, thermistors can provide reasonable linearity and good sensitivity. Many circuits originally constructed with thermistors have over time been updated using silicon temperature sensors.Figure 2. The linearity of thermistors and silicon temperature sensors, two popular analog-output temperature detectors, is contrasted sharply.Silicon temperature sensors come with different output scales and offsets. Some, for example, are available with output transfer functions that are proportional to K, others to °C or °F. Some of the °C parts provide an offset so that negative temperatures can be monitored using a single-ended supply.In most applications, the output of these devices is fed into a comparator or a n A/D converter to convert the temperature data into a digital format. Despite the need for these additional devices,thermistors and silicon temperature sensors continue to enjoy popularity due to low cost and convenience of use in many situations.Digital I/O Temperature SensorsAbout five years ago, a new type of temperature sensor was introduced. These devices include a digital interface that permits communication with a microcontroller. The interface is usually an I²C or SMBus serial bus, but other serial interfaces such as SPI are common. In addition to reporting temperature readings to the microcontroller, the interface also receives instructions from the microcontroller. Those instructions are often temperature limits, which, if exceeded, activate a digital signal on the temperature sensor IC that interrupts the microcontroller. The microcontroller is then able to adjust fan speed or back off the speed of a microprocessor, for example, to keep temperature under control.This type of device is available with a wide variety of features, among them, remote temperature sensing. To enable remote sensing, most high-performance CPUs include an on-chip transistor that provides a voltage analog of the temperature. (Only one of the transistor's two p-n junctions is used.) Figure 3 shows a remote CPU being monitored using this technique. Other applications utilize a discrete transistor to perform the same function.Figure 3. A user-programmable temperature sensor monitors the temperature of a remote CPU's on-chip p-n junction.Another important feature found on some of these types of sensors (including the sensor shown in Figure 3) is the ability to interrupt a microcontroller when the measured temperature falls outside a range bounded by high and low limits. On other sensors, an interrupt is generated when the measured temperature exceeds either a high or a low temperature threshold (i.e., not both). For the sensor in Figure 3, those limits are transmitted to the temperature sensor via the SMBus interface. If the temperature moves above or below the circumscribed range, the alert signal interrupts the processor.Pictured in Figure 4 is a similar device. Instead of monitoring one p-n junction, however, it monitors four junctions and its own internal temperature. Because Maxim's MAX1668 consumes a small amount of power, its internal temperature is close to the ambient temperature. Measuring the ambient temperature gives an indication as to whether or not the system fan is operating properly.Figure 4. A user-programmable temperature sensor monitors its own local temperature and the temperatures of four remote p-n junctions.Controlling a fan while monitoring remote temperature is the chief function of the IC shown in Figure 5. Users of this part can choose between two different modes of fan control. In the PWM mode, the microcontroller controls the fan speed as a function of the measured temperature by changing the duty cycle of the signal sent to the fan. This permits the power consumption to be far less than that of the linear mode of control that this part also provides. Because some fans emit an audible sound at the frequency of the PWM signal controlling it, the linear mode can be advantageous, but at the price of higher power consumption and additional circuitry. The added power consumption is a small fraction of the power consumed by the entire system, though.Figure 5. A fan controller/temperature sensor IC uses either a PWM- or linear-mode control scheme.This IC provides the alert signal that interrupts the microcontroller when the temperature violates specified limits. A safety feature in the form of the signal called "overt" (an abbreviated version of "over temperature") is also provided. If the microcontroller or the software were to lock up while temperature is rising to a dangerous level, the alert signal would no longer be useful. However, overt, which goes active once the temperature rises above a level set via the SMBus, is typically used to control circuitry without the aid of the microcontroller. Thus, in thishigh-temperature scenario with the microcontroller not functioning, overt could be used to shutdown the system power supplies directly, without the microcontroller, and prevent a potentially catastrophic failure.This digital I/O class of devices finds widespread use in servers, battery packs, and hard-disk drives. Temperature is monitored in numerous locations to increase a server's reliability: at the motherboard (which is essentially the ambient temperature inside the chassis), inside the CPU die, and at other heat-generating components such as graphics accelerators and hard-disk drives. Battery packs incorporate temperature sensors for safety reasons and to optimize charging profiles, which maximizes battery life.There are two good reasons for monitoring the temperature of a hard-disk drive, which depends primarily on the speed of the spindle motor and the ambient temperature: The read errors in a drive increase at temperature extremes, and a hard disk's MTBF is improved significantly through temperature control. By measuring the temperature within the system, you can control motor speed to optimize reliability and performance. The drive can also be shut down. In high-end systems, alerts can be generated for the system administrator to indicate temperature extremes or situations where data loss is possible.Analog-Plus Temperature Sensors"Analog-plus" sensors are generally suited to simpler measurement applications. These ICs generate a logic output derived from the measured temperature and are distinguished from digital I/O sensors primarily because they output data on a single line, as opposed to a serial bus.In the simplest instance of an analog-plus sensor, the logic output trips when a specific temperature is exceeded. Some of these devices are tripped when temperature rises above a preset threshold, others, when temperature drops below a threshold. Some of these sensors allow the temperature threshold to be adjusted with a resistor, whereas others have fixed thresholds.The devices shown in Figure 6 are purchased with a specific internal temperature threshold. The three circuits illustrate common uses for this type of device: providing a warning, shutting down a piece of equipment, or turning on a fan.Figure 6. ICs that signal when a temperature has been exceeded are well suited forover/undertemperature alarms and simple on/off fan control.When an actual temperature reading is needed, and a microcontroller is available, sensors that transmit the reading on a single line can be useful. With the microcontroller's internal counter measuring time, the signals from this type of temperature sensor are readily transformed to a measure of temperature. The sensor in Figure 7 outputs a square wave whose frequency is proportional to the ambient temperature in Kelvin. The device in Figure 8 is similar, but the period of the square wave is proportional to the ambient temperature in kelvins.Figure 7. A temperature sensor that transmits a square wave whose frequency is proportional to the measured temperature in Kelvin forms part of a heater controller circuit.Figure 8. This temperature sensor transmits a square wave whose period is proportional to the measured temperature in Kelvin. Because only a single line is needed to send temperature information, just a single optoisolator is required to isolate the signal path.Figure 9, a truly novel approach, allows up to eight temperature sensors to be connected on this common line. The process of extracting temperature data from these sensors begins when the microcontroller's I/O port strobes all the sensors on the line simultaneously. The microcontroller is then quickly reconfigured as an input in order to receive data from each of the sensors. The data are encoded as the amount of time that transpires after the sensors are strobed. Each of the sensors encodes this time after the strobe pulse within a specific range of time. Collisions are avoided by assigning each sensor its own permissible time range.Figure 9. A microcontroller strobes up to eight temperature sensors connected on a common line and receives the temperature data transmitted from each sensor on the same line.The accuracy achieved by this method is surprisingly high: 0.8°C is typical at room temperature, precisely matching that of the IC that encodes temperature data in the form of the frequency of the transmitted square wave. The same is true of the device that uses the period of the square wave.These devices are outstanding in wire-limited applications. For example, when a temperature sensor must be isolated from the microcontroller, costs are kept to a minimum because only one optoisolator is needed. These sensors are also of great utility in automotive and HVAC applications, because they reduce the amount of copper running over distances.Anticipated Temperature Sensor DevelopmentsIC temperature sensors provide a varied array of functions and interfaces. As these devicescontinue to evolve, system designers will see more application-specific features as well as new ways of interfacing the sensors to the system. Finally, the ability of chip designers to integrate more electronics in the same die area ensures that temperature sensors will soon include new functions and special interfaces.中文翻译温度传感器芯片简化设计当选择一个温度传感器时，将不再局限于模拟输出或数字输出设备。
温度控制系统的设计-毕业设计外文文献翻译
Design of the Temperature Control System Based on AT89C51ABSTRACTThe principle and functions of the temperature control system based on micro controller AT89C51 are studied, and the temperature measurement unit consists of the 1-Wire bus digital temperature sensor DS18B20. The system can be expected to detect the preset temperature, display time and save monitoring data. An alarm will be given by system if the temperature exceeds the upper and lower limit value of the temperature which can be set discretionarily and then automatic control is achieved, thus the temperature is achieved monitoring intelligently within a certain range. Basing on principle of the system, it is easy to make a variety of other non-linear control systems so long as the software design is reasonably changed. The system has been proved to be accurate, reliable and satisfied through field practice. KEYWORDS: AT89C51; micro controller; DS18B20; temperature1 INTRODUCTIONTemperature is a very important parameter in human life. In the modern society, temperature control (TC) is not only used in industrial production, but also widely used in other fields. With the improvement of the life quality, we can find the TC appliance in hotels, factories and home as well. And the trend that TC will better serve the whole society, so it is of great significance to measure and control the temperature. Based on the AT89C51 and temperature sensor DS18B20, this system controls the condition temperature intelligently. The temperature can be set discretionarily within a certain range. The system can show the time on LCD, and save monitoring data; and automatically control the temperature when the condition temperature exceeds the upper and lower limit value. By doing so it is to keep the temperature unchanged. The system is of high anti-jamming, high control precision and flexible design; it also fits the rugged environment. It is mainly used in people's life to improve the quality of the work and life. It is also versatile, so that it can be convenient to extend the use of the system. So the design is of profound importance. The general design, hardware design and software design of the system are covered.1.1 IntroductionThe 8-bit AT89C51 CHMOS microcontrollers are designed to handle high-speed calculations and fast input/output operations. MCS 51 microcontrollers are typically used for high-speed event control systems. Commercial applications include modems, motor-control systems, printers, photocopiers, air conditioner control systems, disk drives, and medical instruments. The automotive industry use MCS 51 microcontrollers in engine-control systems, airbags, suspension systems, and antilock braking systems (ABS). The AT89C51 is especially well suited to applications that benefit from its processing speed and enhanced on-chip peripheral functions set, such as automotive power-train control, vehicle dynamic suspension, antilock braking, and stability control applications. Because of these critical applications, the market requires a reliable cost-effective controller with a low interrupt latency response, ability to service the high number of time and event driven integrated peripherals needed in real time applications, and a CPU with above average processing power in a single package. The financial and legal risk of having devices that operate unpredictably is very high. Once in the market, particularly in mission critical applications such as an autopilot or anti-lock braking system, mistakes are financially prohibitive. Redesign costs can run as high as a $500K, much more if the fix means 2 back annotating it across a product family that share the same core and/or peripheral design flaw. In addition, field replacements of components is extremely expensive, as the devices are typically sealed in modules with a total value several times that of the component. To mitigate these problems, it is essential that comprehensive testing of the controllers be carried out at both the component level and system level under worst case environmental and voltage conditions. This complete and thorough validation necessitates not only a well-defined process but also a proper environment and tools to facilitate and execute the mission successfully. Intel Chandler Platform Engineering group provides post silicon system validation (SV) of various micro-controllers and processors. The system validation process can be broken into three major parts. The type of the device and its application requirements determine which types of testing are performed on the device.1.2 The AT89C51 provides the following standard features4Kbytes of Flash, 128 bytes of RAM, 32 I/O lines, two 16-bittimer/counters, a five vector two-level interrupt architecture, a full duple ser-ial port, on-chip oscillatorand clock circuitry. In addition, the AT89C51 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port and interrupt sys -tem to continue functioning. The Power-down Mode saves the RAM contents but freezes the oscil–lator disabling all other chip functions until the next hardware reset.1.3Pin DescriptionVCC Supply voltage.GND Ground.Port 0：Port 0 is an 8-bit open-drain bi-directional I/O port. As an output port, each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high impedance inputs. Port 0 may also be configured to be the multiplexed low order address/data bus during accesses to external program and data memory. In this mode P0 has internal pull ups. Port 0 also receives the code bytes during Flash programming, and outputs the code bytes during program verification. External pull ups are required during program verification.Port 1：Port 1 is an 8-bit bi-directional I/O port with internal pull ups. The Port 1 output buffers can sink/so -urce four TTL inputs. When 1s are written to Port 1 pins they are pulled high by the internal pull ups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled low will source current (IIL) because of the internal pullups. Port 1 also receives the low-order address bytes during Flash programming and verification.Port 2：Port 2 is an 8-bit bi-directional I/O port with internal pull ups. The Port 2 output buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins they are pulled high by the internal pull ups and can be used as inputs. As inputs, Port 2 pins that are externally being pulled low will source current (IIL) because of the internal pull ups. Port 2 emits the high-order address byte during fetches from external program memory and during accesses to Port 2 pins that are externally being pulled low will source current (IIL) because of the internal pull ups. Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that use 16-bit addresses (MOVX@DPTR). In this application, it uses strong internal pull-ups when emitting 1s. During accesses to external data memory that use 8-bit addresses (MOVX @ RI), Port 2 emits the contents of the P2 Special Function Register. Port 2 also receives the high-orderaddress bits and some control signals durin Flash programming and verification.Port 3：Port 3 is an 8-bit bi-directional I/O port with internal pull ups. The Port 3 output buffers can sink/sou -rce four TTL inputs. When 1s are written to Port 3 pins they are pulled high by the internal pull ups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled low will source current (IIL) because of the pull ups.Port 3 also serves the functions of various special features of the AT89C51 as listed below:RST：Reset input. A high on this pin for two machine cycles while the oscillator is running resets the device.ALE/PROG：Address Latch Enable output pulse for latching the low byte of the address during accesses to external memory. This pin is also the program pulse input (PROG) during Flash programming. In normal operation ALE is emitted at a constant rate of 1/6 the oscillator frequency, and may be used for external timing or clocking purposes. Note, however, that one ALE pulse is skipped duri-ng each access to external Data Memory. If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in external execution mode.PSEN：Program Store Enable is the read strobe to external program memory. When theAT89C51 is executing code from external program memory, PSEN is activated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory.EA/VPP：External Access Enable. EA must be strapped to GND in order to enable the device to fetch code from external program memory locations starting at 0000H up to FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset. EA should be strapped to VCC for internal program executions. This pin alsreceives the 12-volt programming enable voltage (VPP) during Flash programming, for parts that require 12-volt VPP.XTAL1：Input to the inverting oscillator amplifier and input to the internal clock operating circuit.XTAL2 ：Output from the inverting oscillator amplifier. Oscillator CharacteristicsXTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier which can be configured for use as an on-chip oscillator, as shownin Figure 1. Either a quartz crystal or ceramic resonator may be used. To drive the device from an external clock source, XTAL2 should be left unconnected while XTAL1 is driven as shown in Figure 2.There are no requirements on the duty cycle of the external clock signal, since the input to the internal clocking circuitry is through a divide-by-two flip-flop, but minimum and maximum voltage high and low time specifications must be observed. Idle Mode In idle mode, the CPU puts itself to sleep while all the on chip peripherals remain active. The mode is invoked by software. The content of the on-chip RAM and all the special functions registers remain unchanged during this mode. The idle mode can be terminated by any enabled interrupt or by a hardware reset. It should be noted that when idle is terminated by a hard ware reset, the device normally resumes program execution, from where it left off, up to two machine cycles before the internal reset algorithm takes control. On-chip hardware inhibits access to internal RAM in this event, but access to the port pins is not inhibited. To eliminate the possibility of an unexpected write to a port pin when Idle is terminated by reset, the instruction following the one that invokes Idle should not be one that writes to a port pin or to external memory.Power-down ModeIn the power-down mode, the oscillator is stopped, and the instruction that invokes power-down is the last instruction executed. The on-chip RAM and Special Function Registers retain their values until the power-down mode is terminated. The only exit from power-down is a hardware reset. Reset redefines the SFRS but does not change the on-chip RAM. The reset should not be activated before VCC is restored to its normal operating level and must be held active long enough to allow the oscillator to restart and stabilize. The AT89C51 code memory array is programmed byte-by byte in either programming mode. To program any nonblank byte in the on-chip Flash Memory, the entire memory must be erased using the Chip Erase Mode.2 Programming AlgorithmBefore programming the AT89C51, the address, data and control signals should be set up according to the Flash programming mode table and Figure 3 and Figure 4. To program the AT89C51, take the following steps.1. Input the desired memory location on the address lines.2. Input the appropriate data byte on the data lines. 3. Activate the correct combination of control signals. 4. Raise EA/VPP to 12V for the high-voltage programming mode. 5. Pulse ALE/PROG once to program a byte in the Flash array or the lock bits. The byte-write cycle is self-timed and typically takes nomore than 1.5 ms. Repeat steps 1 through 5, changing the address and data for the entire array or until the end of the object file is reached. Data Polling: The AT89C51 features Data Polling to indicate the end of a write cycle. During a write cycle, an attempted read of the last byte written will result in the complement of the written datum on PO.7. Once the write cycle has been completed, true data are valid on all outputs, and the next cycle may begin. Data Polling may begin any time after a write cycle has been initiated.2.1Ready/Busy:The progress of byte programming can also be monitored by the RDY/BSY output signal. P3.4 is pulled low after ALE goes high during programming to indicate BUSY. P3.4 is pulled high again when programming is done to indicate READY.Program Verify:If lock bits LB1 and LB2 have not been programmed, the programmed code data can be read back via the address and data lines for verification. The lock bits cannot be verified directly. Verification of the lock bits is achieved by observing that their features are enabled.2.2 Chip Erase:The entire Flash array is erased electrically by using the proper combination of control signals and by holding ALE/PROG low for 10 ms. The code array is written with all “1”s. The chip erase operation must be executed before the code memory can be re-programmed.2.3 Reading the Signature Bytes:The signature bytes are read by the same procedure as a normal verification of locations 030H, 031H, and 032H, except that P3.6 and P3.7 must be pulled to a logic low. The values returned areas follows.(030H) = 1EH indicates manufactured by Atmel(031H) = 51H indicates 89C51(032H) = FFH indicates 12V programming(032H) = 05H indicates 5V programming2.4 Programming InterfaceEvery code byte in the Flash array can be written and the entire array can be erased by using the appropriate combination of control signals. The write operationcycle is self timed and once initiated, will automatically time itself to completion. A microcomputer interface converts information between two forms. Outside the microcomputer the information handled by an electronic system exists as a physical signal, but within the program, it is represented numerically. The function of any interface can be broken down into a number of operations which modify the data in some way, so that the process of conversion between the external and internal forms is carried out in a number of steps. An analog-to-digital converter(ADC) is used to convert a continuously variable signal to a corresponding digital form which can take any one of a fixed number of possible binary values. If the output of the transducer does not vary continuously, no ADC is necessary. In this case the signal conditioning section must convert the incoming signal to a form which can be connected directly to the next part of the interface, the input/output section of the microcomputer itself. Output interfaces take a similar form, the obvious difference being that here the flow of information is in the opposite direction; it is passed from the program to the outside world. In this case the program may call an output subroutine which supervises the operation of the interface and performs the scaling numbers which may be needed for digital-to-analog converter(DAC). This subroutine passes information in turn to an output device which produces a corresponding electrical signal, which could be converted into analog form using a DAC. Finally the signal is conditioned(usually amplified) to a form suitable for operating an actuator. The signals used within microcomputer circuits are almost always too small to be connected directly to the outside world”and some kind of interface must be used to translate them to a more appropriate form. The design of section of interface circuits is one of the most important tasks facing the engineer wishing to apply microcomputers. We have seen that in microcomputers information is represented as discrete patterns of bits; this digital form is most useful when the microcomputer is to be connected to equipment which can only be switched on or off, where each bit might represent the state of a switch or actuator. To solve real-world problems, a microcontroller must have more than just a CPU, a program, and a data memory. In addition, it must contain hardware allowing the CPU to access information from the outside world. Once the CPU gathers information and processes the data, it must also be able to effect change on some portion of the outside world. These hardware devices, called peripherals, are the CPU’s window to the outside.The most basic form of peripheral available on microcontrollers is the generalpurpose I70 port. Each of the I/O pins can be used as either an input or an output. The function of each pin is determined by setting or clearing corresponding bits in a corresponding data direction register during the initialization stage of a program. Each output pin may be driven to either a logic one or a logic zero by using CPU instructions to pin may be viewed (or read.) by the CPU using program instructions. Some type of serial unit is included on microcontrollers to allow the CPU to communicate bit-serially with external devices. Using a bit serial format instead of bit-parallel format requires fewer I/O pins to perform the communication function, which makes it less expensive, but slower. Serial transmissions are performed either synchronously or asynchronously.3 SYSTEM GENERAL DESIGNThe hardware block diagram of the TC is shown in Fig. 1. The system hardware includes the micro controller, temperature detection circuit, keyboard control circuit, clock circuit, Display, alarm, drive circuit and external RAM. Based on the AT89C51, the DS18B20 will transfer the temperature signal detected to digital signal. And the signal is sent to the micro controller for processing. At last the temperature value is showed on the LCD 12232F. These steps are used to achieve the temperature detection. Using the keyboard interface chip HD7279 to set the temperature value, using the micro controller to keep a certain temperature, and using the LCD to show the preset value for controlling the temperature. In addition, the clock chip DS1302 is used to show time and the external RAM 6264 is used to save the monitoring data. An alarm will be given by buzzer in time if the temperature exceeds the upper and lower limit value of the temperature.3.1 HARDWARE DESIGNA. Micro controllerThe AT89C51 is a low-power, high-performance CMOS 8-bit micro controller with 4K bytes of in-system programmable Flash memory. The device is manufactured using At mel’s high-density nonvolatile memory technology and is compatible with the industry-standard 80C51 instruction set and pin out. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with in-system programmable Flash on a monolithic chip, the At mel AT89C51 is a powerful micro controller which provides a highly-flexible and cost-effective solution to manyembedded control applications. Minimum system of the micro controller is shown in Fig. 2. In order to save monitoring data, the 6264 is used as an external RAM. It is a static RAM chip, low-power with 8K bytes memory.B. Temperature Detection CircuitThe temperature sensor is the key part in the system. The Dallas DS18B20 is used, which supports the 1-Wire bus interface, and the ON-BOARD Patented is used internally. All the sensor parts and the converting circuit are integrated in integrated circuit like a transistor [1]. Its measure range is -55℃~125 ℃, and the precision between -10℃~85℃is ±0.5℃[2 ,3]. The temperature collected by the DS18B20 is transmitted in the 1-Wire bus way, and this highly raises the system anti-jamming and makes it fit in situ temperature measurement of the rugged environment [4]. There are two power supply ways for the DS18B20. The first is external power supply: the first pin of the DS18B20 is connected to the ground; the second pin serves as signal wire and the third is connected to the power. The second way is parasite power supply [5]. As the parasite power supply will lead to the complexity of the hardware circuit, the difficulty of the software control and the performance degradation of the chip, etc. But the DS18B20(s) can be connected to the I/O port of the micro controller in the external power supply way and it is more popular. Therefore the external power supply is used and the second pin is connected to the pin P1.3 of the AT89S51. Actually, if there are multipoint to be detected, the DS18B20(s) can be connected to the 1-Wire bus. But when the number is over 8, there is a concern to the driving and the more complex software design as well as the length of the 1-Wire bus. Normally it is no more than 50m. To achieve distant control, the system can be designed in to a wireless one to breakthe length limit of the 1-Wire bus [6].C. LCD CircuitThe LCD 12232F is used, which can be used to show characters, temperature value and time, and supply a friendly display interface. The 12232F is a LCD with 8192 128×32 pixels Chinese character database and 128 16×8 pixels ASCII character set graphics. It mainly consists of row drive/column drive and 128×32 full lattice LCD with the function of displaying graphics as well as 7.5×2 Chinese characters. It is in a parallel or serial mode to connect to external CPU [7]. In order to economize the hardware resource, the 12232F should be connected to the AT89S51 in serial mode with only 4 output ports used. The LCD grayscale can be changed by adjustingthe variable resistor connected the pin Vlcd of the LCD. CLK is used to transmit serial communication clock. SID is used to transmit serial data. CS is used to enable control the LCD. L+ is used to control the LCD backlight power.D. Clock CircuitThe Dallas DS18B20 is used, which is a high performance, low-power and real-time clock chip with RAM. The DS18B20 serves in the system with calendar clock and is used to monitor the time. The time data is read and processed by the AT89C51 and then displayed by the LCD. Also the time can be adjusted by the keyboard. The DS18B20 crystal oscillator is set at 32768Hz, and the recommended compensation capacitance is 6pF. The oscillator frequency is lower, so it might be possible not to connect the capacitor, and this would not make a big difference to the time precision. The backup power supply can be connected to a 3.6V rechargeable battery.E. Keyboard Control CircuitThe keyboard interface in the system is driven by the HD7279A which has a +5V single power supply and which is connected to the keyboard and display without using any active-device. According to the basic requirements and functions of the system, only 6 buttons are needed. The system's functions are set by the AT89C51 receiving the entered data. In order to save the external resistor, the 1×6 keyboard is used, and the keyboard codes are defined as: 07H, 0FH, 17H, 1FH, 27H, 2FH. The order can be read out by reading the code instruction. HD7279A is connected to the AT89S51 in serial mode and only 4 ports are need. As shown in Fig. 6, DIG0~DIG5 and DP are respectively the column lines and row line ports of the six keys which achieve keyboard monitoring, decoding and key codes identification.F. Alarm CircuitIn order to simplify the circuit and convenient debugging, a 5V automatic buzzer is used in the alarm circuit [8]. And this make the software programming simplified. As shown in Fig. 7, it is controlled by the PNP transistor 9012 whose base is connected to the pin P2.5 of the AT89C51. When the temperature exceeds the upper and lower limit value, the P2.5 output low level which makes the transistor be on and then an alarm is given by the buzzer.G. Drive CircuitA step motor is used as the drive device to control the temperature. The four-phase and eight-beat pulse distribution mode is used to drive motor and thesimple delay program is used to handle the time interval between the pulses to obtain different rotational speed. There are two output states for the step motor. One: when the temperature is over the upper value, the motor rotates reversely (to low the temperature), while when lower than the lower limit value, the motor rotates normally (to raise the temperature); besides not equals the preset value. Two: when the temperature is at somewhere between the two ends and equals the preset value, the motor stops. These steps are used to achieve the temperature control. In addition, the motor speed can also be adjusted by relative buttons. As shown in Fig. 8, the code data is input through ports A11~A8 (be P2.3~P2.0) of the AT89C51 and inverted output by the inverter 74LS04. Finally it is amplified by the power amplifier 2803A to power the motor.3.2 SOFTW ARE DESIGNAccording to the general design requirement and hardware circuit principle of the system, as well as the improvement of the program readability, transferability and the convenient debugging, the software design is modularized. The system flow mainly includes the following 8 steps: POST (Power-on self-test), system initiation, temperature detection, alarm handling, temperature control, clock chip DS18B20 operation, LCD and keyboard operation. The main program flow is shown in Fig. 9. Give a little analysis to the above 8 tasks, it is easy to find out that the last five tasks require the real time operation. But to the temperature detection it can be achieved with timer0 timing 1 second, that is to say temperature detection occurs per second. The system initiation includes global variable definition, RAM initiation, special function register initiation and peripheral equipment initiation. Global variable definition mainly finishes the interface definition of external interface chip connected to the AT89C51, and special definition of some memory units. RAM initiation mainly refers to RAM processing. For example when the system is electrified the time code will be stored in the internal unit address or the scintillation flag will be cleared. The special function register initiation includes loading the initial value of timer and opening the interrupt. For example, when the system is electrified the timer is initialized. The peripheral equipment initiation refers to set the initial value of peripheral equipment. For example, when the system is electrified, the LCD should be initialized, the start-up display should be called, the temperature conversion command should be issued firstly and the clock chip DS18B20 should also be initialized. The alarm handling is mainly the lowering and the raising of temperature to make thetemperature remain with the preset range. When the temperature is between the upper and the lower limit value, it goes to temperature control handling, that is to say the temperature need to be raised or lowered according to the preset value. By doing so make the condition temperature equal to the preset value and hence to reach the temperature target.4 CONCLUSIONThe temperature control system has the advantages of friendly human-computer interaction interface, simple hardware, low cost, high temperature control precision (error in the range of ±1 ℃), convenience and versatility, etc. It can be widely used in the occasions with -55℃to 125℃range, and there is a certain practical value.。
DS18B20数字温度计外文资料翻译要点
南京理工大学毕业设计(论文)外文资料翻译学院（系）：专业：机电一体化工程姓名：学号：外文出处：from internet附件： 1.外文资料翻译译文；2.外文原文。
指导教师评语：该外文资料贴近本次毕业设计主题，有一定的权威性，翻译的较全面，符合外文资料翻译要求。
签名：2014 年 5 月附件1：外文资料翻译译文DS18B20 数字温度计描述DS18B20 数字温度计提供9至12位温度读数，指示器件的温度。
信息经过单线接口送入DS18B20或送出，因此从中央处理器到DS18B20仅需连接一条（和地）。
读、写和完成温度变换所需的电源可以有数据线本身提供，而不需要外部电源。
因为每一个DS18B20有唯一的系列号，因此多个DS18B20可以存在于同一条单线总线上。
这允许在许多不同的地方放置温度灵敏器件。
此特性的应用范围包括HVAC环境控制，建筑物、设备或机械内的温度检测，以及过程监视和控制中的温度检测。
特性独特的单线接口，只需一个接口引脚即可通信。
多点能力使分布式温度检测应用得以简化。
不需要外部元件。
可用数据线供电，提供3.0V到5.5V的电源。
不需备份电源。
测量范围从-55°C 到+125°C，等效的华氏温标范围是-67°F 到+257°F以9到12位数字值方式读出温度。
在750毫秒内把12位温度变换为数字。
用户可定义的，非易失性的温度警告设置。
告警搜索命令识别和寻址温度在编定的极限之外的器件（温度告警情况）。
应用范围包括恒温控制，工业系统，消费类产品，温度计或任何热敏系统。
引脚排列引脚说明GND –地DQ –数字输入输出VDD –可选的VDDNC –不连接详细引脚说明综述图1的方框图表示DS18B20的主要部件。
DS18B20有三个主要的数据部件：1）64为激光ROM，2）温度灵敏元件，3）非易失性温度告警触发器TH和TL。
器件从单线的通信线取得其电源，在信号线为高电平的时间周期内，把能量贮存在内部的电容器中，在单信号线为低电平的时间期内断开此电源，直到信号线变为高电平重新接上寄生（电容）电源为止，作为另一种可供选择的方法，DS18B20也用外部5V电源供电。
毕业设计外文翻译英文翻译英文原稿
Harmonic source identification and current separationin distribution systemsYong Zhao a，b，Jianhua Li a，Daozhi Xia a,*a Department of Electrical Engineering Xi’an Jiaotong University, 28 West Xianning Road, Xi’an, Shaanxi 710049, Chinab Fujian Electric Power Dispatch and Telecommunication Center, 264 Wusi Road, Fuzhou, Fujian, 350003, China AbstractTo effectively diminish harmonic distortions, the locations of harmonic sources have to be identified and their currents have to be separated from that absorbed by conventional linear loads connected to the same CCP. In this paper, based on the intrinsic difference between linear and nonlinear loads in their V –I characteristics and by utilizing a new simplified harmonic source model, a new principle for harmonic source identification and harmonic current separation is proposed. By using this method, not only the existence of harmonic source can be determined, but also the contributions of the harmonic source and the linear loads to harmonic voltage distortion can be distinguished. The detailed procedure based on least squares approximation is given. The effectiveness of the approach is illustrated by test results on a composite load.2004 Elsevier Ltd. All rights reserved.Keywords: Distribution system; Harmonic source identification; Harmonic current separation; Least squares approximation1. IntroductionHarmonic distortion has experienced a continuous increase in distribution systems owing to the growing use of nonlinear loads. Many studies have shown that harmonics may cause serious effects on power systems, communication systems, and various apparatus [1–3]. Harmonic voltages at each point on a distribution network are not only determined by the harmonic currents produced by harmonic sources (nonlinear loads), but also related to all linear loads (harmonic current sinks) as well as the structure and parameters of the network. To effectively evaluate and diminish the harmonic distortion in power systems, the locations of harmonic sources have to be identified and the responsibility of the distortion caused by related individual customers has to be separated.As to harmonic source identification, most commonly the negative harmonic power is considered as an essential evidence of existing harmonic source [4–7]. Several approaches aiming at evaluating the contribution of an individual customer can also be found in the literatures. Schemes based on power factor measurement to penalize the customer’s harmonic currents are discussed in Ref. [8]. However, it would be unfair to use economical penalization if we could not distinguish whether the measured harmonic current is from nonlinear load or from linear load.In fact, the intrinsic difference between linear and nonlinear loads lies in their V –I characteristics. Harmonic currents of a linear load are i n linear proportion to its supplyharmonic voltages of the same order 次, whereas the harmonic currents of a nonlinear load are complex nonlinear functions of its supply fundamental 基波and harmonic voltage components of all orders. To successfully identify and isolate harmonic source in an individual customer or several customers connected at same point in the network, the V –I characteristics should be involved and measurement of voltages and currents under several different supply conditions should be carried out.As the existing approaches based on measurements of voltage and current spectrum or harmonic power at a certain instant cannot reflect the V –I characteristics, they may not provide reliable information about the existence and contribution of harmonic sources, which has been substantiated by theoretical analysis or experimental researches [9,10].In this paper, to approximate the nonlinear characteristics and to facilitate the work in harmonic source identification and harmonic current separation, a new simplified harmonic source model is proposed. Then based on the difference between linear and nonlinear loads in their V –I characteristics, and by utilizing the harmonic source model, a new principle for harmonic source identification and harmonic current separation is presented. By using the method, not only the existence of harmonic source can be determined, but also the contributions of the harmonic sources and the linear loads can be separated. Detailed procedure of harmonic source identification and harmonic current separation based on least squares approximation is presented. Finally, test results on a composite load containing linear and nonlinear loads are given to illustrate the effectiveness of the approach.2. New principle for harmonic source identification and current separationConsider a composite load to be studied in a distribution system, which may represent an individual consumer or a group of customers supplied by a common feeder 支路in the system. To identify whether it contains any harmonic source and to separate the harmonic currents generated by the harmonic sources from that absorbed by conventional linear loads in the measured total harmonic currents of the composite load, the following assumptions are made.(a) The supply voltage and the load currents are both periodical waveforms withperiod T; so that they can be expressed by Fourier series as1()s i n (2)h h h v t ht T πθ∞==+ (1)1()sin(2)h h h i t ht πφ∞==+The fundamental frequency and harmonic components can further be presented bycorresponding phasorshr hi h h hr hi h hV jV V I jI I θφ+=∠+=∠ , 1,2,3,...,h n = (2)(b) During the period of identification, the composite load is stationary, i.e. both its composition and circuit parameters of all individual loads keep unchanged.Under the above assumptions, the relationship between the total harmonic currents of the harmonic sources(denoted by subscript N) in the composite load and the supply voltage, i.e. the V –I characteristics, can be described by the following nonlinear equation ()()()N i t f v t = (3)and can also be represented in terms of phasors as()()122122,,,...,,,,,,...,,Nhr r i nr ni Nh Nhi r inr ni I V V V V V I I V V V V V ⎡⎤=⎢⎥⎣⎦ 2,3,...,h n = (4)Note that in Eq. (4), the initial time (reference time) of the voltage waveform has been properly selected such that the phase angle u1 becomes 0 and 10i V =, 11r V V =in Eq. (2)for simplicity.The V –I characteristics of the linear part (denote by subscript L) of the composite load can be represented by its equivalent harmonic admittance Lh Lh Lh Y G jB =+, and the total harmonic currents absorbed by the linear part can be described as,Lhr LhLh hr Lh Lhi LhLh hi I G B V I I B G V -⎡⎤⎡⎤⎡⎤==⎢⎥⎢⎥⎢⎥⎣⎦⎣⎦⎣⎦2,3,...,h n = (5)From Eqs. (4) and (5), the whole harmonic currents absorbed by the composite load can be expressed as()()122122,,,...,,,,,,...,,hr Lhr Nhr r i nr ni h hi Lhi Nhi r inr ni I I I V V V V V I I I I V V V V V ⎡⎤⎡⎤⎡⎤==-⎢⎥⎢⎥⎢⎥⎣⎦⎣⎦⎣⎦ 2,3,...,h n = (6)As the V –I characteristics of harmonic source are nonlinear, Eq. (6) can neither be directly used for harmonic source identification nor for harmonic current separation. To facilitate the work in practice, simplified methods should be involved. The common practice in harmonic studies is to represent nonlinear loads by means of current harmonic sources or equivalent Norton models [11,12]. However, these models are not of enough precision and new simplified model is needed.From the engineering point of view, the variations of hr V and hi V ; ordinarily fall into^3% bound of the rated bus voltage, while the change of V1 is usually less than ^5%. Within such a range of supply voltages, the following simplified linear relation is used in this paper to approximate the harmonic source characteristics, Eq. (4)112222112322,ho h h r r h i i hnr nr hni ni Nh ho h h r r h i i hnr nr hni ni a a V a V a V a V a V I b b V b V b V b V b V ++++++⎡⎤=⎢⎥++++++⎣⎦2,3,...,h n = (7)这个地方不知道是不是原文写错？23h r r b V 其他的都是2The precision and superiority of this simplified model will be illustrated in Section 4 by test results on several kinds of typical harmonic sources.The total harmonic current (Eq. (6)) then becomes112222112222,2,3,...,Lh Lh hr ho h h r r h i i hnr nr hni ni h Lh Lh hi ho h h r r h i i hnr nr hni ni G B V a a V a V a V a V a V I B G V b b V b V b V b V b V h n-++++++⎡⎤⎡⎤⎡⎤=-⎢⎥⎢⎥⎢⎥++++++⎣⎦⎣⎦⎣⎦= (8)It can be seen from the above equations that the harmonic currents of the harmonic sources (nonlinear loads) and the linear loads differ from each other intrinsically in their V –I characteristics. The harmonic current component drawn by the linear loads is uniquely determined by the harmonic voltage component with same order in the supply voltage. On the other hand, the harmonic current component of the nonlinear loads contains not only a term caused by the same order harmonic voltage but also a constant term and the terms caused by fundamental and harmonic voltages of all other orders. This property will be used for identifying the existence of harmonic source sin composite load.As the test results shown in Section 4 demonstrate that the summation of the constant term and the component related to fundamental frequency voltage in the harmonic current of nonlinear loads is dominant whereas other components are negligible, further approximation for Eq. (7) can be made as follows.Let112'012()()nh h hkr kr hki ki k k h Nhnh h hkr kr hki kik k h a a V a V a V I b b V b V b V =≠=≠⎡⎤+++⎢⎥⎢⎥=⎢⎥⎢⎥+++⎢⎥⎢⎥⎣⎦∑∑ hhr hhi hr Nhhhr hhi hi a a V I b b V ⎡⎤⎡⎤''=⎢⎥⎢⎥⎣⎦⎣⎦hhrhhihr Lh Lh Nh hhrhhi hi a a V I I I b b V ''⎡⎤⎡⎤'''=-=⎢⎥⎢⎥''⎣⎦⎣⎦,2,3,...,hhr hhiLh Lh hhrhhi hhr hhi Lh Lh hhr hhi a a G B a a h n b b B G b b ''-⎡⎤⎡⎤⎡⎤=-=⎢⎥⎢⎥⎢⎥''⎣⎦⎣⎦⎣⎦The total harmonic current of the composite load becomes112012(),()2,3,...,nh h hkr kr hki ki k k hhhrhhi hr h Lh NhLhNh n hhrhhi hi h h hkr kr hki kik k h a a V a V a V a a V I I I I I b b V b b V b V b V h n=≠=≠⎡⎤+++⎢⎥⎢⎥''⎡⎤⎡⎤''=-=-=-⎢⎥⎢⎥⎢⎥''⎣⎦⎣⎦⎢⎥+++⎢⎥⎢⎥⎣⎦=∑∑ (9)By neglecting ''Nh I in the harmonic current of nonlinear load and adding it to the harmonic current of linear load, 'Nh I can then be deemed as harmonic current of thenonlinear load while ''Lh I can be taken as harmonic current of the linear load. ''Nh I =0 means the composite load contains no harmonic sources, while ''0NhI ≠signify that harmonic sources may exist in this composite load. As the neglected term ''Nh I is not dominant, it is obviousthat this simplification does not make significant error on the total harmonic current of nonlinear load. However, it makes the possibility or the harmonic source identification and current separation.3. Identification procedureIn order to identify the existence of harmonic sources in a composite load, the parameters in Eq. (9) should be determined primarily, i.e.[]0122hr h h h rh i hhr hhihnr hni C a a a a a a a a ''= []0122hi h h h rh i hhrhhihnr hni C b b b b b b b b ''=For this purpose, measurement of different supply voltages and corresponding harmoniccurrents of the composite load should be repeatedly performed several times in some short period while keeping the composite load stationary. The change of supply voltage can for example be obtained by switching in or out some shunt capacitors, disconnecting a parallel transformer or changing the tap position of transformers with OLTC. Then, the least squares approach can be used to estimate the parameters by the measured voltages and currents. The identification procedure will be explained as follows.(1) Perform the test for m （2m n ≥）times to get measured fundamental frequency andharmonic voltage and current phasors ()()k k h h V θ∠,()()k k hh I φ∠,()1,2,,,1,2,,k m h n == .(2) For 1,2,,k n = ，transfer the phasors corresponding to zero fundamental voltage phase angle ()1(0)k θ=and change them into orthogonal components, i.e.()()11kkr V V = ()10ki V =()()()()()()()()()()11cos sin kkkkk kkkhr h h hihhV V h V V h θθθθ=-=-()()()()()()()()()()11cos sin k kkkk kkkhrhhhihhI I h I I h φθφθ=-=-,2,3,...,h n =(3)Let()()()()()()()()1221Tk k k k k k k k r i hr hi nr ni VV V V V V V V ⎡⎤=⎣⎦ ,()1,2,,k m = ()()()12Tm X V V V ⎡⎤=⎣⎦ ()()()12T m hr hr hr hrW I I I ⎡⎤=⎣⎦()()()12Tm hi hi hihi W I I I ⎡⎤=⎣⎦ Minimize ()()()211hr mk hr k I C V=-∑ and ()()()211him k hi k IC V=-∑, and determine the parametershr C and hi C by least squares approach as [13]:()()11T T hr hr T T hi hiC X X X W C X X X W --== (10)(4) By using Eq. (9), calculate I0Lh; I0Nh with the obtained Chr and Chi; then the existence of harmonic source is identified and the harmonic current is separated.It can be seen that in the course of model construction, harmonic source identification and harmonic current separation, m times changing of supply system operating condition and measuring of harmonic voltage and currents are needed. More accurate the model, more manipulations are necessary.To compromise the needed times of the switching operations and the accuracy of the results, the proposed model for the nonlinear load (Eq. (7)) and the composite load (Eq. (9)) can be further simplified by only considering the dominant terms in Eq. (7), i.e.01111,Nhr h h hhr hhi hr Nh Nhi ho h hhrhhi hi I a a V a a V I I b b V b b V +⎡⎤⎡⎤⎡⎤⎡⎤==+⎢⎥⎢⎥⎢⎥⎢⎥+⎣⎦⎣⎦⎣⎦⎣⎦2,3,,h n = (11) 01111h h Nh ho h a a V I b b V +⎡⎤'=⎢⎥+⎣⎦01111,hr hhrhhi hr h h h LhNh hi hhr hhihi ho h I a a V a a V I I I I b b V b b V ''+⎡⎤⎡⎤⎡⎤⎡⎤''==-=-⎢⎥⎢⎥⎢⎥⎢⎥''+⎣⎦⎣⎦⎣⎦⎣⎦2,3,,h n = (12) In this case, part equations in the previous procedure should be changed as follows[]01hr h h hhrhhi C a a a a ''= []01hi h h hhrhhiC b b b b ''= ()()()1Tk k k hr hi V V V ⎡⎤=⎣⎦ Similarly, 'Nh I and 'Lh I can still be taken as the harmonic current caused by thenonlinear load and the linear load, respectively.4. Experimental validation4.1. Model accuracyTo demonstrate the validity of the proposed harmonic source models, simulations are performed on the following three kind of typical nonlinear loads: a three-phase six-pulse rectifier, a single-phase capacitor-filtered rectifier and an acarc furnace under stationary operating condition.Diagrams of the three-phase six-pulse rectifier and the single-phase capacitor-filtered rectifier are shown in Figs. 1 and 2 [14,15], respectively, the V –I characteristic of the arc furnace is simplified as shown in Fig. 3 [16].The harmonic currents used in the simulation test are precisely calculated from their mathematical model. As to the supply voltage, VekT1 is assumed to be uniformly distributed between 0.95 and 1.05, VekThr and VekThi ek 1; 2;…;m T are uniformly distributed between20.03 and 0.03 with base voltage 10 kV and base power 1 MVFig. 1. Diagram of three-phase six-pulse rectifier.Fig. 2. Diagram of single-phase capacitor-filtered rectifierFig. 3. Approximate V –I characteristics of arc furnace.Three different models including the harmonic current source (constant current) model, the Norton model and the proposed simplified model are simulated and estimated by the least squares approach for comparison.For the three-phase six-pulse rectifier with fundamental currentI=1.7621; the1 parameters in the simplified model for fifth and seventh harmonic currents are listed in Table 1.To compare the accuracy of the three different models, the mean and standard deviations of the errors on Ihr; Ihi and Ih between estimated value and the simulated actual value are calculated for each model. The error comparison of the three models on the three-phase six-pulse rectifier is shown in Table 2, where mhr; mhi and mha denote the mean, and shr; shi and sha represent the standard deviations. Note that I1 and _Ih in Table 2are the current values caused by rated pure sinusoidal supply voltage.Error comparisons on the single-phase capacitor-filtered rectifier and the arc furnace load are listed in Table 3 and 4, respectively.It can be seen from the above test results that the accuracy of the proposed model is different for different nonlinear loads, while for a certain load, the accuracy will decrease as the harmonic order increase. However, the proposed model is always more accurate than other two models.It can also be seen from Table 1 that the componenta50 t a51V1 and b50 t b51V1 are around 20:0074 t0:3939 0:3865 and 0:0263 t 0:0623 0:0886 while the componenta55V5r and b55V5i will not exceed 0:2676 ￡0:03 0:008 and 0:9675 ￡0:003 0:029; respectively. The result shows that the fifth harmonic current caused by the summation of constant term and the fundamental voltage is about 10 times of that caused by harmonic voltage with same order, so that the formal is dominant in the harmonic current for the three-phase six-pulse rectifier. The same situation exists for other harmonic orders and other nonlinear loads.4.2. Effectiveness of harmonic source identification and current separationTo show the effectiveness of the proposed harmonic source identification method, simulations are performed on a composite load containing linear load (30%) and nonlinear loads with three-phase six-pulse rectifier (30%),single-phase capacitor-filtered rectifier (20%) and ac arc furnace load (20%).For simplicity, only the errors of third order harmonic current of the linear and nonlinear loads are listed in Table 5, where IN3 denotes the third order harmonic current corresponding to rated pure sinusoidal supply voltage; mN3r ;mN3i;mN3a and mL3r ;mL3i;mL3a are error means of IN3r ; IN3i; IN3 and IL3r ; IL3i; IL3 between the simulated actual value and the estimated value;sN3r ;sN3i;sN3a and sL3r ;sL3i;sL3a are standard deviations.Table 2Table 3It can be seen from Table 5 that the current errors of linear load are less than that of nonlinear loads. This is because the errors of nonlinear load currents are due to both the model error and neglecting the components related to harmonic voltages of the same order, whereas only the later components introduce errors to the linear load currents. Moreover, it can be found that more precise the composite load model is, less error is introduced. However, even by using the very simple model (12), the existence of harmonic sources can be correctly identified and the harmonic current of linear and nonlinear loads can be effectively separated. Table 4Error comparison on the arc furnaceTable 55. ConclusionsIn this paper, from an engineering point of view, firstly anew linear model is presented for representing harmonic sources. On the basis of the intrinsic difference between linear and nonlinear loads in their V –I characteristics, and by using the proposed harmonic source model, a new concise principle for identifying harmonic sources and separating harmonic source currents from that of linear loads is proposed. The detailed modeling and identification procedure is also developed based on the least squares approximation approach. Test results on several kinds of typical harmonic sources reveal that the simplified model is of sufficient precision, and is superior to other existing models. The effectiveness of the harmonic source identification approach is illustrated using a composite nonlinear load.AcknowledgementsThe authors wish to acknowledge the financial support by the National Natural Science Foundation of China for this project, under the Research Program Grant No.59737140. References[1] IEEE Working Group on Power System Harmonics, The effects of power system harmonics on power system equipment and loads. IEEE Trans Power Apparatus Syst 1985;9:2555–63.[2] IEEE Working Group on Power System Harmonics, Power line harmonic effects on communication line interference. IEEE Trans Power Apparatus Syst 1985;104(9):2578–87.[3] IEEE Task Force on the Effects of Harmonics, Effects of harmonic on equipment. IEEE Trans Power Deliv 1993;8(2):681–8.[4] Heydt GT. Identification of harmonic sources by a State Estimation Technique. IEEE Trans Power Deliv 1989;4(1):569–75.[5] Ferach JE, Grady WM, Arapostathis A. An optimal procedure for placing sensors and estimating the locations of harmonic sources in power systems. IEEE Trans Power Deliv 1993;8(3):1303–10.[6] Ma H, Girgis AA. Identification and tracking of harmonic sources in a power system using Kalman filter. IEEE Trans Power Deliv 1996;11(3):1659–65.[7] Hong YY, Chen YC. Application of algorithms and artificial intelligence approach for locating multiple harmonics in distribution systems. IEE Proc.—Gener. Transm. Distrib 1999;146(3):325–9.[8] Mceachern A, Grady WM, Moncerief WA, Heydt GT, McgranaghanM. Revenue and harmonics: an evaluation of someproposed rate structures. IEEE Trans Power Deliv 1995;10(1):474–82.[9] Xu W. Power direction method cannot be used for harmonic sourcedetection. Power Engineering Society Summer Meeting, IEEE; 2000.p. 873–6.[10] Sasdelli R, Peretto L. A VI-based measurement system for sharing the customer and supply responsibility for harmonic distortion. IEEETrans Instrum Meas 1998;47(5):1335–40.[11] Arrillaga J, Bradley DA, Bodger PS. Power system harmonics. NewYork: Wiley; 1985.[12] Thunberg E, Soder L. A Norton approach to distribution networkmodeling for harmonic studies. IEEE Trans Power Deliv 1999;14(1):272–7.[13] Giordano AA, Hsu FM. Least squares estimation with applications todigital signal processing. New York: Wiley; 1985.[14] Xia D, Heydt GT. Harmonic power flow studies. Part I. Formulationand solution. IEEE Trans Power Apparatus Syst 1982;101(6):1257–65.[15] Mansoor A, Grady WM, Thallam RS, Doyle MT, Krein SD, SamotyjMJ. Effect of supply voltage harmonics on the input current of single phase diode bridge rectifier loads. IEEE Trans Power Deliv 1995;10(3):1416–22.[16] Varadan S, Makram EB, Girgis AA. A new time domain voltage source model for an arc furnace using EMTP. IEEE Trans Power Deliv 1996;11(3):1416–22.。
温度变送器规格书
1 仪表名称 Instrument Name 类型 Type 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 测温元件型号 Therm. Element 分度号 Type 允差等级 Tolerance Error Rating 测量端形式 Junction Style 保护套形式 Well Type 保护套管材质 Well Mat'l 压力等级 Pressure Rating 保护套管外径 Well Outside Dia. 过程连接形式 Process Conn. 连接规格 Size 法兰标准 Flange STD. 等级 Rating 法兰材质 Flange Mat'l 密封面形式 Facing 变送器型号 Trans. Model 输入信号 Input Signal 输出信号 Output Signal 校准量程 Calibration Range 精度 Accuracy 电源 Power Supply 最大负载 Max. Load 接线盒形式 Terminal Box Style 电气连接 Elec.Conn. 防护等级 Enclosure Protection 防爆等级 Explosion Proof 安装位置 Mounting Position 输出信号指示表 Out. Sign. Indic.(0-100 Linear) 安装支架 Mounting Bracket
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版本 FA
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TT302 温度变送器概述TT302温度变送器接收毫伏(mV)输出的信号，这类传感器包括热电偶或阻性传感器，例如：热电阻（RTD）。
它所接受的信号必须在允许的输入范围之内。
允许输入电压范围为-50到500，电阻范围为0到2000欧姆。
功能描述-硬件每个板的功能介绍如下：图2.1 TT302-硬件构成方框图多路转换器多路转换器将变送器端子接到相应信号调理板上，以保证在正确的端子上测量电压。
信号调理板他的作用给输入信号提供一个正确的值以满足A/D转换。
A/D转换器A/D转换器将输入信号转换成数字形式传给CPU。
信号隔离他的作用在输入和CPU之间隔离控制信号和数字信号。
中央处理单元（CPU）RAM PROM和EEPROMCPU是变送器的智能部分，主要完成测量，板的执行，自诊断和通信的管理和运行。
系统程序存储在PROM中。
RAM用于暂时存放运算数据。
在RAM中存放的数据一旦断电立即消失，所以数据必须保存在不易丢失的EEPROM中。
例如：标定，块的标识和组态等数据。
通信控制器监视在线动态，调整通信信号，插入，删除预处理，滤波。
电源变送器电路通过现场总线电源供电。
电源隔离像信号隔离一样，供给输入部分的信号必须要隔离，电源隔离采用变压器将直流供电电源转换成高频交流供电。
显示控制器从CPU接收数据送给LCD显示器的显示部分，此时显示器必须处于打开状态。
本机调整它有两个磁性驱动开关，它们必须由磁性工具来驱动而不是机械或电的接触。
图2.2-LCD指示器温度传感器TT302像前面所描述的那样，可以兼容多种类型的传感器。
TT302为使用热电偶或热电阻RTD 测量温度进行了特殊设计。
此类传感器的基本内容如下所述：热电偶热电偶由两种不同的金属或合金在一端连接在一起所组成的，被称为测量端或热端。
测量端必须放在测量点上，热电偶的另一端是打开的连接在温度变送器上，这一端称做参考端或冷端。
在大多数应用中，塞贝克效应可以充分解释热电偶的工作原理。
热电偶是如何工作的（塞贝克效应）当金属丝的两端有温差时，在金属丝的没一端都会产生一个小的电动势，这种现象就叫做塞贝克效应。
当两种不同金属丝连接在一起，而另一端开放时，两端之间的温差将会产生一个电压输出。
现在，有两个重要的问题需要注意：首先，热电偶所产生的电压与测量端和冷端的温度成比例，因此，为了得到被测温度必须加上参考端的温度，被称做冷端温度补偿。
TT302可以自动进行补偿。
为此，在TT302传感器端子装有一个温度传感器。
其次，如果热电偶与变送器端子之间的导线没有采用与热电偶相同的导线（例如：由热电偶传感器或接线盒到变送器端子之间采用铜线）那么就会对温度测量产生影响，因此必须要进行冷端补偿。
热电偶的电势在冷端温度为0℃时与热端温度的关系用热电偶分度表来表示。
分度表存储在TT302的存储器中，他们是国际标准NBS(B,E,J,K,N,R,S,T)和德国工业标准DIN(L,U) 热电阻（RTD）热电阻通常被称做RTD，它的工作原理是金属的阻抗会随着温度的升高而增加，存储在TT302的中的热电阻分度表有日本工业标准JIS[1604-81] (Pt50,Pt100)。
国际电工委员会IEC,DIN,JIS[1604-89] (Pt50,Pt100&Pt500)，通用电气公司GE(Cu10)和DIN(Ni120)。
为使热电阻能够正确测量温度，必须消除传感器到测量电路之间线路电阻所造成的影响。
在一些工业应用中，这些导线有几百米长，在环境温度变化剧烈的场所，消除线路电阻的影响是极为重要的。
TT302允许二线制连接，但可能会引起测量误差。
此误差取决于接线的长度和导线经过处的温度（图2.3二线制连接）在二线制连接中，电压U2与热电阻的阻值R TD和导线的电阻R成正比U2=(R TD+2R X I图2.3二线制连接为了避免导线电阻的影响，推荐用三线制连接（图2.4三线制连接）或四线制连接（图2.5三线制连接）在三线制连接中，端子3是高阻抗输入端，因此，没有电流流过该导线，此导线上也没有压降。
电压U2-U1与电阻无关，因为导线电阻上的电压被抵消掉了，它仅与R TD的电阻有关。
U2-U1=(R TD+R)X I-RxI=R TDx I图2.4 三线制连接在四线制连接中，端子2和端子3是高阻抗输入端，因此，没有电流流过此端，也没有压降产生。
另外两根导线的电阻可不予考虑，这两根导线上也没有测量点，因此电压U2只与R TD电阻值有关U2=R TDx I图2.5四线制连接双通道连接和二线制连接相似，也存在相同的问题（图2.6双通道连接）导线的电阻需要测量，而且在同一温度下测量也不能忽略他们的阻值，因为长度也会影响使它们不同。
图2.6双通道连接西门子SIMATIC PCS 7 PS 展望投资成本低标准化的系统基于标准化的部件，因此有高度的挠性和可变性。
由于标准化技术的使用使其具有开放性运行和维护成本低全自动化具有电厂设备所需的控制系统的特殊功能和部件顾客利益与设备的适应性强可根据电厂的规模和特性进行扩展和改变可改变它的性能和记忆功能由一个服务器来实现从单一控制到分散控制具备电厂所需的特殊运行，监视，诊断和过程接口回顾自1997年投入市场截止到2002年8月100﹪的销售率在30多个国家投入使用控制领域：工业发电厂生物发电厂电厂单元机组的辅机成功的原因全自动化功率方案库的使用将SIMATIC PCS 7的兼容性增强创新性应用国际公认标准为控制和HMI提供一种开放系统服务范围无论何时何地都可得到全球范围内的服务经验在工程和节约时间方面提供高质量的规划，管理和方案技术认证过热器与再热器过热器是一种将热量传给饱和蒸汽以提高其温度的换热器。
蒸汽过热是中心电站所采用的设计特点之一，过热增加了整体循环效率。
另外，它降低了汽轮机末级叶片的湿度，因此提高了汽机的内在效率。
一般而言，过热器可分为辐射式过热器、对流式过热器或联合式过热器，这取决于热量是怎样从烟气传给蒸汽的。
这些过热器具有不同的运行特性，在机组负荷的宽范围内如能保持出口汽温不变，这样的特性是最希望的。
当出口汽温变得过高，则会引起过热器因部分过热而失效。
对流过热器位于炉膛出口，或能够从燃烧的高温产物吸收热能的区域。
对流过热器常常通过一束水冷管来遮蔽炉膛辐射热。
当这些管子留有足够的间隔时，也能遮断渣粒而减少过热器上的结渣问题。
在大型蒸汽发生器系统中，对流过热器常常分为两部分：一级过热器和二级过热器。
饱和蒸汽首先进入一级过热器而接受初始过热，一级过热器为于相对低的烟温区，在部分过热后，蒸汽进到二级过热器而完成其过热过程。
使过热器分为两级的主要原因是为蒸汽再热器提供一个空间，使烟气向蒸汽有效传热。
辐射过热器没有对流过热器那样得到普遍使用。
当需要辐射过热器时，它通常位于炉膛壁上代替一端水冷管。
另一种布置是使辐射过热器刚好在屏式管后面，辐射过热器是二级过热器的中间部分。
中心电站锅炉提供蒸汽再热。
再热器一般是对流式，且通常位于一级与二级过热器之间的空间。
当蒸汽温度在汽机中部分膨胀后，它返回锅炉再热。
离开再热器的蒸汽温度通常等于过热蒸汽温度。
因为再热器的设计在运行本质上与过热器一样，过热器的讨论将同样适用于再热器。
在过热器的热力设计中，首先确定蒸汽温度。
一般而言这点在电站系统设计中完成，以平衡电站初始费用和服役期运行费用。
近年来，对于所有蒸汽发生器系统，最佳蒸汽温度约538℃。
热力设计中的第二步是近似确定所要求的过热器面积数量。
在过热器表面积被确定后，下一步要考虑的是选择管子的长度、管径和管子数。
显然，选择是一个反复的过程，先产生一个尝试解，查看其各种约束是否满足，从各种可接受解中找到最优解。
最佳过热器应该有给予设计汽温所必需的足够的传热表面。
管子参数（长度和直径）使得蒸汽压降和管子金属温度将不超过设计值。
管子金属温度是一个重要参数，对管子材料的选择有很大影响。
另外，最佳过热器要使管子布置得使所产生的灰和渣最少。
现代过热器有许多管子通道，管子都顺排布置而不用错排布置。
管子通常是圆管，外径为5或6.3cm。
没有附在管子上的扩展表面（如肋片），材料的选择取决于蒸汽温度和压力。
碳钢的允许温度达430℃，常常用于低温过热器。
铬-钼钢、不锈钢或某种类似的耐热合金能承受高达650℃的温度，因而它们被选做高温区过热器。
温度调节与控制对过热器与再热器都很重要，蒸汽温度调节常常要在锅炉指定的时间内进行，原则方法是增加或减少传热面积。
蒸汽温度也可以通过调节热烟气温度和质量流量来实现。
一般而言，这些都是通过改变过量空气或者蒸发段效果来完成。
在锅炉运行中，有许多因素影响离开过热器和再热器的蒸汽温度，它们包括锅炉负荷、过量空气、给水温度和受热面的清洁度。
运行中蒸汽温度的控制必须在不改变设备布置的情况下完成，最有效的措施包括：烟气旁路，燃烧器控制，温度调节，烟气再循环，过量空气以及分隔炉膛。
烟气旁路是控制烟气流过过热器的流量，这种方法是主要缺点是高温区可动闸板操作运行困难，且对负荷变化响应慢。
燃烧器控制通常是控制火焰位置和燃烧速度，使燃烧器倾斜可以使火焰指向或离开过热器，这将改变炉膛的吸热和过热器的烟气温度。
随着锅炉负荷减小，燃烧器将逐一推出运行，这将改变燃烧速度，从而改变流经过热器的烟气流量。
温度调节是常使用的方法之一，温度调节器通常位于一级和二级过热器之间。
有两种基本形式的温度调节器：一种是管式，一部分过热蒸汽通过换热器管道，将热量传给锅炉水（可以是锅炉给水或锅炉汽包水），随后进入温度调节，从一级过热器分开的蒸汽将会合，一起进入二级过热器；第二种温度调节器是将给水喷入过热蒸汽流中。
给水蒸发使蒸汽温度降低，控制给水量就可以控制蒸汽温度。
必须注意要使喷水足够纯净，喷水要和过热蒸汽很好地混合，从而使得第二级过热器的入口没有水滴。
烟气再循环通常采用改变炉膛和过热器的吸收率来控制蒸汽温度，当需要蒸汽温度声高时，从省煤器出口取出的一部分烟气将循环返回炉膛底部。
因此，炉膛温度降低，导致炉膛吸热减少，而炉膛出口烟温升高。
这么高的烟温，加上烟气流量增加，将增加过热器的传热速率，使蒸汽出口温度升高。
温度控制也受所使用的过量空气量的影响，过量空气越多，蒸汽出口温度将越高，其原因与烟气再循环方法的原因类似。
必须指出，太多的过量空气将导致锅炉燃烧效率降低。
分隔炉膛锅炉是将饱和蒸汽的生产安排在一段，而将过热蒸汽的生产安排在另一段。
过热汽温是通过控制两个炉膛中的燃烧速率来调节的，这一方法不经济，很少应用中心电站锅炉。
译文：TT302—Field bus Temperature TransmitterOperationThe TT302 accepts signals from mV generators such as thermocouples or resistive sensors such asRTDs. The criterion is that the signal is within the range of the input. For mV, the range is -50 to 500mV and for resistance, 0-2000 Ohm.Functional Description – HardwareThe function of each block is described below.Figure 2.1—TT302Block DiagramMUX MultiplexerThe MUX multiplexes the sensor terminals to the signal conditioning section ensuring that the voltages are measured between the correct terminals.Signal ConditionerIts function is to apply the correct gain to the input signals to make them suit the A/D -converter. A/D ConverterThe A/D converts the input signal to a digital format for the CPU.Signal IsolationIts function is to isolate the control and data signal between the input and the CPU.(CPU) Central Processing Unit, RAM, PROM and EEPROMThe CPU is the intelligent portion of the transmitter, being responsible for the management and operation of measurement, block execution, self-diagnostics and communication. The program is stored in a PROM. For temporary storage of data there is a RAM. The data in the RAM is lost if the power is switched off. However there is a nonvolatile EEPROM where data that must be retained is stored. Examples, of such data are trim, calibration, block configuration andidentification data.TT302 - Fieldbus Temperature TransmitterCommunication ControllerIt monitors line activity, modulates and demodulates communication signals and inserts and deletes start and end delimiters.Power SupplyTakes power of the loop-line to power the transmitter circuitry.Power IsolationJust like the signals to and from the input section, the power to the input section must be isolated. Isolation is achieved by converting the DC supply into a high frequency AC supply and galvanically separating it using a transformer.Display ControllerReceives data from the CPU informing which segments of the Liquid Crystal Display, should be turned on.Local AdjustmentThere are two switches that are magnetically activated. They can be activated by the magnetic tool without mechanical or electrical contact.Figure 2.2 - LCD IndicatorTemperature SensorsThe TT302, as previously explained, accepts several types of sensors. The TT302 is specially designed for temperature measurement using thermocouples or Resistive Temperature Detectors (RTDs).Some basic concepts about these sensors are presented below.ThermocouplesThermocouples are constructed with two wires made from different metals or alloys joined at one end, called measuring junction or "hot junction". The measuring junction should be placed at the point of measurement. The other end of the thermocouple is open and connected to the temperaturetransmitter. This point is called reference junction or cold junction.For most applications, the Seebeck effect is sufficient to explain thermocouple behavior as following:How the Thermocouple Works (Seebeck Effect)When there is a temperature difference along a metal wire, a small electric potential, unique to every alloy, will occur. This phenomenon is called Seebeck effect. When two wires of dissimilar metals are joined at one end, and left open at the other, a temperature difference between the two ends will result in a voltage since the potentials generated by the dissimilar materials are different and do not cancel each other out. Now, two important things must be noted. First: the voltage generated by the thermocouple is proportional to the difference between the measuring-junction and the cold junction temperatures. Therefore the temperature at the reference junction must be added to the temperature derived from the thermocouple output, in order to find the temperature measured. This is called cold junction compensation, and is done automatically by the TT302, which has a temperature sensor at the sensor terminals for this purpose. Secondly, if the thermocouple wires are not used, all the way to the terminals of the transmitter (e.g., copper wire is used from sensor-head or marshaling box) will form new junctions with additional Seebeck effects. It will be created and ruin the measurement in most cases, since the cold-junction compensation will be done at the wrong point.NOTEThe relation between the measuring junction temperature and the generated mili-voltage is tabulated in thermocouple calibration tables for standardized thermocouple types, the reference temperature being 0 oC.Standardized thermocouples that are commercially used, whose tables are stored in the memory of the TT302, are the following:. NBS (B, E, J, K, N, R, S & T). DIN (L & U)Resistive Temperature Detectors (RTDs)Resistance Temperature Detectors, most commonly known as RTD’s, are based on the principle that the resistance of metal increases as its temperature increases. Standardized RTDs, whose tables are stored in the memory of the TT302, are the following:. JIS [1604-81] (Pt50 & Pt100). IEC, DIN, JIS [1604-89] (Pt50, Pt100 & Pt500).. GE (Cu10).. DIN (Ni120)For correct measurement of RTD temperature, it is necessary to eliminate the effect of the resistance of the wires connecting the sensor to the measuring circuit. In some industrial applications, these wires may be hundreds of meters long. This is particularly important at locations where the ambient temperature changes constantly.The TT302 permits a 2-wire connection that may cause measuring errors, depending on the length of connection wires and on the temperature to which they are exposed. (See Figure 2.3 -Two-Wire Connection).In a 2-wire connection, the voltage V2 is proportional to the RTD resistance plus the resistance of the wires.V2 = [RTD + 2 x R] x IFigure 2.3 - Two-Wire ConnectionIn order to avoid the resistance effect of the connection wires, it is recommended to use a 3-wire connection (See Figure 2.4 – Three-Wire Connection) or a 4-wire connection (See Figure 2.5 - Four - Wire Connection).In a 3-wire connection, terminal 3 is a high impedance input. Thus, no current flows through that wire and no voltage drop is caused. The voltage V2-V1 is independent of the wire resistances since they will be cancelled, and is directly proportional to the RTD resistance alone.V2-V1 =[RTD + R] x I - R x I = R TD x IFigure 2.4 - Three – Wire ConnectionIn a 4-wire connection, terminals 2 and 3 are high impedance inputs. Thus, no current flows through those wires and no voltage drop is caused. The resistance of the other two wires is not of interest, since there is no measurement registered on them. Hence the voltage V2 is directly proportional to the RTD resistance.(V2 = RTD x I)Figure 2.5 - Four - Wire ConnectionA differential or dual channel connection is similar to the two-wire connection and gives the same problem (See Figure 2.6 - Differential or Dual Connection). The resistance of the wires will be measured and do not cancel each other out in a temperature measurement, since linearization will affect them differently.Figure 2.6 - Differential or Dual ConnectionSIEMENSHighlight of SIMATIC PCS 7 PSLow investment costs．Modular system based on standard components, therefore high degree of flexibility and scalability.．Open thanks to the use of standard technologies.Low operation and maintenance costs．Horizontal integration with Totally Integrated Automation.．Control system specific functionality and components for power plant requirements.Customer Profits．Optimum adaptation to the requirements.．Expansion and adaptations according to size and plant characteristic.．Scalable performances and memories for control.．Scalable from single station to distributed control system with client-server architecture. ．Power-plant-specific operation and monitoring,diagnostics and process interface.Facts& Figures of Simatic PCS7 PSThe Scope．On the market since 1997.．100 sold to date (as of 08/2002).．In use in more than 30 countries.．In control of:Industrial power plantsBiomass power plantsAuxiliaries of power plantsReasons behind this success．Totally Integrated Automation:Consistent use of SIMATIC PCS7 with Power Solution Library．Innovation Nature:We provide an open system using international recognized standards for control and HMI ．Competence:Worldwide services which are available for you anytime, anywhere!．Experience:Project management and process know-how guarantee for high quality in project engineering and saving time.Superheater and ReheaterThe superheater is a heat exchanger in which heat is transferred to the saturated steam to increase its temperature. Stream superheating is one of the design features accepted in central electric power stations. Superheating raise overall cycle efficiency. In addition, it reduces a moisture level in the last stages of the steam turbine and thus increases the turbine internal efficiency.Superheaters are commonly classified as either radiant superheaters, convective superheaters, or combined superheaters, depending on how heat id transferred from the gases to steam. These superheaters have different performance characteristics. The feature that the outlet steam temperature can stay essentially constant over a wide range of unit load is the most desirable. When the outlet steam temperature becomes excessive, it may cause failures from overheating parts of the superheater.The convective superheater is located in the furnace exit or in the zone where it can receivethermal energy from the high temperature produces of combustion. The convective superheater is frequently screened from the furnace radiation by a bank of water-filled tubes. These tubes, when adequately spaced, can also intercept the slag particle and reduce slagging problems in superheatrs. Convective superheaters in large steam generator systems are frequently split into two parts: the primary superheater and the secondary superheaater. Saturated steam first enters the primary superheater and receives the initial heating. The primary superheater is located in a zone of relatively low gas temperature. After the partial heating steam moves to the secondary superheater and completes its superheaing process. The main reasons for splitting the superheater are to provide space for the steam reheater and to achieve an effective heat transfer from the gases the steam.The radiant superheater is not as commonly used as the convective superheater. When the radiant superheater is needed, it is usually placed on the furnace wall replacing a section of water-filled tubes. Another arrangement is to have the radiant superheater just behind the screen tubes. The radiant superheater is an integral part of the secondary superheater.Central station boilers provide for steam reheating. The reheater is essentially a convective type and usually located in the space between thee primary and secondary superheaters. After steam partially expands in the tubine, it returns to the boiler for reheating. The temperature of steam leaving the reheater is usually equal to the superheated steam temperature. Since the design and operation of reheater are essentially the same as superheaters, the discussion of superheaters will be equally applicable to reheaters.In superheater thermal design, the steam temperature is first determined. This is generally accomplished in the plant system design, balancing the plant initial cost against the lifttime operating cost. In recent years the optimum steam temperature is approximately 538℃for all large steam generation systems. In the second step, the amount of superheater surface required is approximated.After the amount of superheater surface id determined, the next consideration is to select the tube length, tube diameter, and the number of tubes. Evidently, the selection is an iterative process, generating a trial solution and checking to see whether all constraints are met. From several acceptable solutions, the optimum is found. The optimum superheater should have enough heat transfer surface necessary to give the design steam temperature. The tube parameters(length and diameter) are such that the steam pressure drop and tube metal temperature will not exceed the design values. The tube metal temperature is an important parameter and has a strong influence on the tube material selection. In addition, the optimum superheater should have its tubes so spaced that minimum ash and slag deposits will result.Modern superheaters have many tube passes, and the tubes are arranged in-line rather than staggered. The tubes are usually cylindrical and have 5 or 6.3cm outside diameter. There is no extended surface(i.e.fins)attached to the tubes. The material selection depends on the steam temperature and pressure. Carbon steel has an allowable temperature up to 430℃and is frequently used for loe-temperature superheaters. Chrome-moly, stainless steel, or same similar heat resistant alloy can withstand the temperature up to 650℃. Therefore they are selected for theSuperheater in a high-temperature zone.Temperature regulation and control are importation for both superheaters andreheaters. Steam temperature adjustments are frequently made at the time of the commissioning of a boiler. The principal methods are an addition or regulatingthe hot gas temperature and mass flow rate. These are generally accomplished by changing the excess air or the effectiveness of the evaporation section.During a boiler operation, there are many factors affecting the temperature of steam leaving the superheater and reheater. These include a boiler load, excessair, feedwater temperature, and cleanliness of heating surfaces. Control of steamtemperature during operation must be done without changing the arrangement of equipment. The most effective approaches are gas bypass, burner control, attemperation, gas recirculation, excess air, divided furnace.A gas bypass is to control the gas flow rate to superheater. The main disadvantages of this approach are the operating difficulties experienced by the movable dampers located in the high-temperature zone and the slow response to load change.Burner control is used to control the flame location and combustion rate. Tilting burners can direct the flame toward or away from the superheater. These will result in a change of heat absorption in the furnace and change of gas temperature in the superheater. As the boiler load is reduced, burners are removed one by one from service. This will change the combustion rate and, thus, change the gas flow rate to the superheater.Attemperation is one of approaches frequently used. The attemperator is usually located at the point between the primary and secondary superheaters.There are two basic types of attemperator. The first is the tubular type in which some of superheated steam is passed through the tubes of a heat exchanger and has heat transferred to the boiler water(either boiler feedwater or water in the boiler drum).Subsequent to attemperation, the divided streams from the primary superheater will combine and enter the secondary superheater.The second type of attemperator involves a spray of feedwater into the atream ofsuperheated steam. The feedwater evaporates and reduces the steam temperature. Controlling the amount of feedwater will result in control of the ateam temperature. Care must be exercised to ensure that the spray water has sufficient purity. The spray water should mix well with the superheated steam so that there are no water droplets in the inlet of the secondary superjeater.Gas recirculation is used to control the steam temperature by changing the heat absorption rates both in the furnace and in the superheater. When the ateam temperature needs to be raised, some of the furnace. Therefore, the furnace temperature will become lower, resulting in a lower heat absorption in the furnace and thereby a higher flue gas temperature in the furnace exit. This high gas temperature, combined with an increase in the gas floe rate, will increase the heat transfer rate in the superheater and thus increase the steam outlet temperature.Temperature control can be affected bu using different amounts of excess air. the more the excess air, the higher the steam outlet temperature would be. The reasons for this are similar to those for the gas recirculation method. It must be pointed out, however, that too much excess air will result in a reduction of boiler combustion efficiency. A divided-furnace boiler is usually arranged with a generation of saturated steam in one section and a superheating of steam in another section. The temperature of the superheated steam is regulated by controlling the firing rates in the two furnaces. This method is not economical and is seldom applied in a central electric power station.。