I'm having to check several circuits with many capacitors in them.
I have heard of using the following tools:
1. capacitor testor - for out of circuit tests (measure leakage &
2. ESR meter - to check equivalent series resistance while capacitor is in
A third method is to look at the signal over a capacitor in a live
circuit with an oscilloscope. If the capacitor is good the AC component
should be small. The advantage of this method is that you see how the
capacitor behaves under real live conditions. The disadvantage is that
for circuits like the primary side of a SMPS this method can be
dangerous to your health.
What is the best method(s) of checking capacitors? Or what methods would you
use and in what order?
An ESR meter is ideal for quickly identifying suspect electrolytic caps.
It is the first method I use. It catches the vast majority of bad
electrolytic caps. However a decent ESR is not a 100% guarantee that the
capacitor is good. Like any in-circuit test other components, like
parallel capacitors, may confuse the readings. You still need to
understand what you are doing. But most of the time it works perfectly,
and not having to remove capacitors from the circuit board is a real
If the ESR meter is unable to identify you might resort to testing
capacitors out of circuit with a real capacitor tester (not the one you
find on multimeters, these are useless). However before you do that you
want to narrow down the possible number of suspects to test. Desoldering
every capacitor on the PCB and putting the good ones back is usually not
a good idea.
Do you have any specific suggestions on models on instruments you like to
That depends on how much you are willing to spend on it and how
intensively you are going to use it. Is it just for hobby or are trying
to make living out of this?
If it is just for hobby take a look at this one:
I have this ESR meter myself, and I'm quite impressed with the build
quality of this unit. It is certainly good value for money.
Unfortunately it lacks a beeper, which makes it is less suitable for
really intensive use.
For other ESR meters look here: