Unless you're going to be testing caps in the field rather than in the lab, wouldn't a bog-standard USB power supply be preferable for this project? 5V would give you more options than 3V and have a greater chance of achieving that magic 5% accuracy you want.

 

Unless you're going to be testing caps in the field rather than in the lab, wouldn't a bog-standard USB power supply be preferable for this project? 5V would give you more options than 3V and have a greater chance of achieving that magic 5% accuracy you want.

5% is not a magic number . If overall accuracy is 10 or 20% , it's OK. It's not for exact measurement. ESR values may differ significantly .
In other hand, i don't want to use a primitive one-transistor meter, you can't trust at all. Those are discussed in many forums. Simply read the feedback

 

bob2,
i did read the feedback. Bizzare shaped test voltage,frequency is not stable, poor performance, especially if battery is depleted

BobTPH,
A typical PP3 9V battery have small capacity, high self-discharge and relatively high cost.
I prefer rechargeable NiMh AAA type

How often do you intend to use it?

 

Any comments on circuit post #40?
Did anybody build a similar oscillator?

 

This improves output waveform significally.

Why are you concerned about waveform?

 

Why are you concerned about waveform?

sine wave signal meters are less sensitive to parasitic parameters , like capacitor ESL and probe self inductance

 

100kHz sine vawe oscillator from internet. The author said simutated in LT Spice, THD about 10%, amplitude remains 2mVp-p when powered from 2 to 2.9V battery.
The current source is built on VT3, LED ,R1 and R3. This improves output waveform significally.
Amplifier gain is set with R8-R9.

A nice little circuit, I like it!
Is the resistor in series with the cap-under-test the actual ESR?

 

A nice little circuit, I like it!
Is the resistor in series with the cap-under-test the actual ESR?
View attachment 298530

Yes

 

i did read the feedback. Bizzare shaped test voltage,frequency is not stable, poor performance, especially if battery is depleted

The shape of the signal does not affect the result. The scale is stretched near zero.

 

The shape of the signal does not affect the result. The scale is stretched near zero.

no, no, indeed, it's not. They said-
Firs of all, it was appeared in a russian site. Discussed for a long time.
Take a look, how it's made- yellow epoxy coated, it seems, they invented an eternal NiCd battery