ESR meter DIY

One way to test electrolytic capacitors is to measure their capacitance. It does not tell the whole story of capacitor condition. Another usually more useful way to measure electrolytic capacitor condition is to use an ESR meter. Here is ESR meter I built years ago based on instructions from http://ludens.cl/Electron/esr/esr.html
but I built the transformer differently from parts I had (took toroidal inductor and wound extra coil).

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Inside

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Circuit diagram

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The design presented here works by applying a 50kHz, 200mV square wave to the capacitor under test, in series with a 10 Ohm resistor.

The circuit diagram shows a transformer with very many turns on primary and secondary. I replaced the transformer with my ow transformer that had the same turns ratio, but when I used a large ferrite toroidal core, I could build transformer with similar other specifications with less turns.

Some more ESR meter material
https://www.epanorama.net/blog/2013/01/17/esr-meters/

This ESR meter has advantage of working better with in-circuit capacitors than smart multi component testers.

Those smart testers can measure nicely ESR from bare components not in circuit board:
https://www.epanorama.net/blog/2019/09/17/component-tester-case/
https://www.epanorama.net/blog/2015/09/09/component-tester-m12864/
https://www.epanorama.net/blog/2018/03/26/transistor-tester-m12864-advaced-version/
https://www.epanorama.net/blog/2014/08/18/diy-electronics-tester-kit-m168/

4 Comments

  1. CM Tan says:

    You are lucky to get this ESR to work. Technically TL062 requires a minimum of +5V and -5V, which means that 9V with virtual ground at +4.5V is insufficient. Please refer to datasheet at para 6.3. Refer also tp para 6.7 under VICR and VOM. Technically 9V is not enough under all cases. You might happen to have use some very good spec TL062. TL082 is slightly better specs on these points, but even with TL082, 9V is not enough. I would use at least 12V (+6V and -6V) if the signal translation is not more than 3Vp-p at the input or output. Any larger signal will cause signal distortion or worst output inversion.

    Reply
  2. CM Tan says:

    You are lucky to get this ESR to work. Technically TL062 requires a minimum of +5V and -5V, which means that 9V with virtual ground at +4.5V is insufficient. Please refer to datasheet at para 6.3. Refer also tp para 6.7 under VICR and VOM. Technically 9V is not enough under all cases. You might happen to have use some very good spec TL062. TL082 is slightly better specs on these points, but even with TL082, 9V is not enough. I would use at least 12V (+6V and -6V) if the signal translation is not more than 3Vp-p at the input or output. Any larger signal will cause signal distortion or worst output inversion.

    Reply
  3. CM Tan says:

    I have a greatly improved design, based on Luden’s design. There are several issues with Luden’s design which I have corrected. It will help you improve your mid scale deflection to 5 ohms or less instead of the 25 ohms you are having now.
    Refer to https://electronicsdesignfun.blogspot.com/p/esr-meter.html

    Reply

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