电容ESR

ESR & Low Resistance Meter
Introduction
As electrolytic capacitors age, their internal resistance - Equivalent Series Resistance (ESR) - increases & eventually
causes faulty operation of the circuit. This device can measure the ESR & can be also used to measure small
resistances..

Circuit Description
IC1a is configured as an oscillator. IC2a divides this signal by 2 to ensure a 50/50 mark/space ratio.

IC3a switches between +5 Volt and ¨5Volt and thus applies an AC square wave current of about 2 mA to the capacitor
under test Cx. IC3b/1,2 directs the positive half cycles to C9 and IC3b/3,4 directs the negative ones to C10. R4, C9 &
C10 act as low pass filters to attenuate the 100 kHz AC component of the voltage across Cx. C9 & C10 charge to the
DC component which is proportional to the ESR. C9 holds the positive voltage during negative half cycles and C10
holds the negative voltage during positive half cycles.

IC4 amplifies the differential DC signal so it can be displayed on a Digital Multimeter (on the 200mV scale). 10 Ohm
will be represented by 100 mV, 1 Ohm by 10 mV, etc.

Calibration
Adjust P1 to obtain 100 kHz at TP3.

Connect the probes together and adjust P4 for 0mV at IC4/6.

Separate the probes. Set P2 to balance the positive & negative currents through R2 as follows. Apply -5V to TP2.
Connect a multimeter between TP4 and B and note the current (about 2 mA). Transfer the -5V from TP2 to TP1 and
adjust P2 until the same current (magnitude, ignore sign) is obtained. Remove the -5V from TP1.

Connect the Multimeter between A & B. Apply the probes to a 10 Ohm resistor and adjust P3 until the Multimeter
reads 100 mV.

Protection against charged capacitors.
Always ensure that the capacitor under test is discharged before measuring its ESR. However, accidents will happen, so
R3, D1 & D2 protect against capacitors charged to at least 20 Volt. R4, D3 & D4 to at least 32 Volt. If the voltage is
greater than these, survival of these components will depend upon the energy stored in the capacitor which is dependant
upon the voltage and capacitance.

Len Cox
Forest Hill
Australia



血沉及低电阻测试仪
简介
电解电容器的年龄，他们的内部阻力 - 等效串联电阻（ESR） - 增加和最终
导致电路故障。该装置可以测量的ESR及也可以用来测量小
电阻..

电路描述
IC1a配置为振荡器。 IC2a这2分，以确保信号50/50马克/空间比例。

IC3a之间切换5伏和° 5Volt，因而适用于交流方波约2 mA电流的电容器
根据试验Cx。 IC3b / 1,2指示正半周期C9和IC3b / 3,4消极的指示到C10。 R4中，碳九及
C10的低通滤波器来衰减行为100千赫Cx的两端电压的交流分量。碳九和C10的充电至
直流成分，是成正比的ESR。碳九负半周期间举办和C10的正电压
保存在负电压正半周期。

IC4的放大差分直流

信号，它可以在数字万用表显示（在200mV的规模）。 10欧姆
将代表100毫伏，10毫伏1欧姆等

校准
调整小一获得100 TP3千赫。

探针连接在一起，在IC4的调整/ 6 0mV P4的。

独立的探头。设置P2到平衡，R2的正，负电流如下。适用─5V至TP2上。
之间连接一个TP4和乙万用表，并注意电流（约2毫安）。转自TP2上的- 5V至TP1和
调整到相同的电流为P2（大小，忽略符号）获得。 TP1还取出了- 5V的。

A和B之间连接万用表应用到10欧姆的电阻探针和P3的调整，直到万用表
读取100毫伏。

防护电容器充电。
始终确保被测电容的ESR测量其前出院。然而，天有不测风云，所以
R3中，D1和D2防止收取至少20伏电容。 R4中，维生素D3和D4的至少32伏。如果电压
比这些更重要，这些组件的生存将取决于在电容中储存的能量，取决于
根据电压和电容。


莱恩考克斯
福里斯特希尔
澳大利亚