Posted on Monday, May 2, 2011 • Category:
Test and Measurement
As electrolytic capacitors age, their internal resistance, also known as "equivalent series resistance" (ESR), gradually increases. This can eventually lead to equipment failure. Using this design, you can measure the ESR of suspect capacitors as well as other small resistances. Basically, the circuit generates a low-voltage 100kHz test signal, which is applied to the capacitor via a pair of probes. An op amp then amplifies the voltage dropped across the capacitor’s series resistance and this can be displayed on a standard multimeter. In more detail, inverter IC1d is configured as a 200kHz oscillator.
Its output drives a 4027 J-K flipflop, which divides the oscillator signal in half to ensure an equal mark/space ratio. Two elements of a 4066 quad bilateral switch (IC3c & IC3d) are alternately switched on by the complementary outputs of the J-K flipflop. One switch input (pin 11) is connected to +5V, whereas the other (pin 8) is connected to -5V. The outputs (pins 9 & 10) of these two switches are connected together, with the result being a ±5V 100kHz square wave. Series resistance is included to current-limit the signal before it is applied to the capacitor under test via a pair of test probes. Diodes D1 and D2 limit the signal swing and protect the 4066 outputs in case the capacitor is charged.
Digital Volt Ampere Meter ESR & Low Resistance Test Meter Function Generator XR2206 Dual Channel 70V PIC Voltmeter LM386 Audio Probe Amplifier Simple EMF Probe ESR Meter / Transistor Tester PIC based Spectrum Analyser for PC 10Hz - 60MHz Frequency Meter / Counter Accurate LC Meter based on PIC16F84ACircuit-Zone.com © 2007-2025. All Rights Reserved.
