Author Topic: An ESR Meter to Check Capacitors  (Read 3077 times)

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An ESR Meter to Check Capacitors
« on: November 21, 2012, 12:30:43 pm »
I just completed my ESR Meter to check for bad electrolytic capacitors.  It operates at 250mV so it will not turn on transistors, so you can use it for in circuit troubleshooting.  When electrolytic capacitors dry up, and they frequently do, they stop behaving like capacitors and you get voltage ripple.  This is the reason why a lot of computers, monitors, and routers fail.   

Wikipedia explains the theory of operation the best:
An ESR meter is a two-terminal electronic measuring instrument designed and used primarily to measure the equivalent series resistance (ESR) of real capacitors - the ESR of an ideal capacitor is zero - usually without the need to disconnect the capacitor from the circuit it is connected to. Most ESR meters work by applying voltage pulses to the capacitor under test which are too short to appreciably charge it; any voltage appearing across the capacitor is due to ohmic drop across the ESR

This meter is my implementation of an already existing schematic available on the internet.

A photo of my ESR Capacitor Meter:

<photo available soon>

I sourced all electronics parts from Digikey, the project enclosure from Radio Shack,  and the Analog meter is a 50uA current meter sourced from Fleabay (aka

If you want to make your own,  I have attached the artwork for the analog meter scale as well as the meter.  I used ink jet printable decal slide paper (available from Ebay) to make my own custom decals. 

Full size file:

Full size file:

« Last Edit: November 24, 2012, 03:43:41 pm by »