温度和压力传感器

temperature sensor and Pressure sensor

introduction

Pressure Sensor

The pressure sensor is an industrial practice, Instrument control the most commonly used sensors, And widely For a variety of industrial automation environment,Involvingwaterutilities,Railwaytransport,Productionautomation, Aerospace, Military, Petrochemical ,oil, electricity, shipbuilding , machine tools, pipes and many other industries .

Many types of mechanical sensors ,Such as resistance strain gauge pressure sensors, Semiconductor strain gauge pressure sensor, A piezo resistive pressure sensors, pressure sensors inductive, capacitive pressure sensors, resonant pressure transmission Capacitive sensors and acceleration sensors. But the most widely used is the piezo resistive pressure sensors, it has Low price and high accuracy and good linearity. Here we introduce this type of sensor.

Piezoresistive pressure sensor principle and applications:

Piezoresistive pressure sensor is the use of single crystal silicon piezoresistive material made of effects and integrated circuit technology transfer Sensors, Piezoresistive sensors commonly used in pressure Rally ,Other physical pressure difference and can change into force Physical quantity ( such as level , acceleration , weight, strain , flow rate , degree of vacuum) for measurement and control. Piezoresistive effect

When force is applied to the silicon crystal , the crystal lattice deformation

,The carriers from one valley to another can valley scattering, Caused by the mobility of carriers is changed , the disturbance of the longitudinal and transverse carriers of the average amount ,Thereby changing the resistivity of silicon .This varies with the crystal orientation varies ,Therefore, silicon piezoresistive effect Should be concerned with the orientation of the crystal .Unlike silicon piezoresistive effect metal strain gauges, The former resistance changes with pressure Depend on the resistance change rate , which depends mainly on the change of the resistance change of the geometry ( to be Variable ) , and the sensitivity of the former than the latter 50~100 Times.

Piezoresistive pressure sensor structure Piezoresistive pressure sensor with integrated process will be integrated on a single crystal silicon resistance of the diaphragm, Made of silicon piezoresistive Chip, This chip peripherals and fixed encapsulated within the housing , the lead electrode leads. Piezoresistive pressure sensor Is also known as solid-state pressure sensor ,It differs from the bonded strain gauge sensing element required by the elastic vicarious Force ,But directly feel the pressure measured by the silicon diaphragm .Silicon diaphragm side is connected with the measured pressure High-pressure chamber ,The other surface is a low pressure chamber communicating with the atmosphere .Silicon diaphragm is generally designed to be clamped round ,Straight Diameter and thickness ratio of about 20~60.In a circular silicon diaphragm(Type)Localized diffusion 4 Article P Resistance of impurities,

And then Sake of the bridge , which is located two compressive stress zone , and the other two in the tensile stress zone , relative to the center of the diaphragm symmetry. Silicon is also a cylindrical element diffusion sensitive resistive strip produced in a certain direction on a cylindrical silicon crystal plane, Two by Tensile stress resistance of compressive stress with another two full bridge resistance of the constitution .

Development

1954 In C.S. Smith detailed study of the piezoresistive effect of silicon, silicon manufacturers began using pressure sensor Devices . Early silicon pressure sensor is a semiconductor strain gauge type . Later in the N Given the proliferation of domain -type silicon wafer P Type impurity resistivity of the formation , and then into the bridge, made chips. This chip still attached to the elastic member Sensitive to changes in pressure . With this chip as the sensing element of the sensor is called diffusion -type pressure sensor.

Both sensors are also used sticky sheet structure ,Thus there is a large hysteresis and creep ,Natural frequency is low, Unwell Dynamic measurements, and difficult to miniaturization and integration, accuracy is not the disadvantages .70 Made since the era of the Week Side fixed support the resistance and the integration of the silicon diaphragm diffused silicon pressure sensor cup .It not only overcomes the sticky Sheet structure of the inherent defects ,And can resistive strip ,Compensation circuitry and signal conditioning circuitry integrated on a silicon chip On Even the micro-processor integrated with sensors, Made smart sensors .