Another piece of test gear that I’ve been needing for a while is an ESR meter. W2AEW has a video on his youtube channel about a simple 5 transistor ESR meter that was designed by an eevblog forum user.
I had everything I needed to build it except for a 50uA meter, but ebay had plenty for a few bucks.
The schematic is below, but I’d really suggest watching W2AEW’s video where he walks through the circuit and explains it in detail.
I built the circuit on a piece of perf board and hooked up the meter with some alligator leads.
Since it is the holiday season, I was able to find a cookie tin that was about the right size for the enclosure.
I usually have trouble drilling into these tins. Drill bits tear up the thin metal, but this time I tried a few diamond tipped hole saws with my drill press and they worked beautifully.
I mounted everything and just hot glued the circuit to the lid.
Here it is all together.
I shorted the leads together and zeroed the meter with the pot.
Here it is measuring a 1 ohm resistor.
Below is a 2.2 ohm resistor.
And a 10 ohm resistor.
As you can see, it is working. The scale is very non-linear and I still need to calibrate it and replace the paper scale in the meter itself, but it is pretty easy to tell at a glance if you’ve got a bad cap. I’d definitely suggest building one of these if you need an ESR meter.