configure esr for noncharted caps

f caps that are not on the charts and don't have access to data sheets?

Approach 1: look up a table of typical values. Hit & miss, inevitably. Approach 2: use a bridge. Simple, yes. Quick, not really.

ir lower R limit is basic & only useful for electrolytics.

NT

Is there a simple way to do something that wasn't easy in the first place?

No.

RL

Yes.

Start with a power resistor chosen to place a substantial current load on the charged capacitor. Switch the bottom (ground) end of the resistor with a power MOSFET, drive the MOSFET from a pulse generator. Use your scope in its ac-coupled mode to see the step changes in voltage vs load on-off across the capacitor terminals. To keep it all honest, move the probe from the top to the bottom of the cap to verify the voltage step change, as opposed to ground-wiring voltage drops.

This will work, but I prefer an HP LCR meter with variable test frequency and milli-ohm sensitivity. Get them used on eBay. I like the hp 4192A.

What equipment do you have?

He doesn't have an oscilloscope!

Here's a 50 ohm function generator making a square wave into an electrolytic cap. You can see C, ESR, and ESL in the waveform.

Time domain rules!

To quote JL: "He doesn't have an oscilloscope!"

My square wave trick might work. Or do it in the frequency domain: inject a sine wave current, sweep the frequency, measure the terminal voltage. It should be a sort of bathtub curve, with the low, flat part defining ESR.

But they have an ESR app:

Is that the same Robert Macy that used to post here?

Cheers