ESR or Capacitance Meter???

[Andyd1970]

Hi Guys,

Really getting into repairing TV's now with thanks to TOM66 who is a real star and has taught me a few things.

I am looking to get an ESR meter but a friend said why not get a capacitance meter instead, so I was wondering if anyone could clarify between the two types.

I believe a ESR can be used without removing the caps, and the capacitance meter has to have the caps desoldered first.

Also any recommendations on a good unit for someone who is going to repair a TV or two.

Andy

[1supertech]

Re: ESR or Capacitance Meter???

Yes you’re correct
But as far as using a Esr meter if caps are in series you will get false reading I notice this on motherboards but for power supplies Esr meter is a time saver. for caps lower then 0.1UF I us a capacitance meter.

EDS -88A ESR METER
M6013 AUTO RANGING CAPACITOR TESTER

[mariushm]

Re: ESR or Capacitance Meter???

Capacitance checker will measure the capacitance
ESR meter will measure the ESR.

They are two different things.

The capacitance is not a very useful value to know when repairing stuff. The capacitors themselves can have +/- 20% variation and the tool itself is only about +/- 1-5% when it comes to measure the capacitance.

Furthermore, most capacitance meters only use low voltage to determine capacitance, usually up to 2v - this works for low voltage rated capacitors but not so well for 200-400v rated capacitors.

The capacitors may be bad but the capacitance may still be reported within that 20% tolerance by a meter because the meter only charges the capacitor up to a few volts.

Of particular importance is the case of ceramic capacitors - the capacitance of ceramic capacitors is hugely dependent on voltage going through them: depending on type, a 10uF 16v ceramic capacitor will have 10uF at 1v, 8uF at 3-4v and can have as low as 1-2uF at 10v. A multimeter won't catch this issue.


The measurements are also done at low frequency not at frequencies commonly used in power supplies (above hearing level, generally 37Khz-100kHz). On lots of capacitors, the capacitance changes with frequency.

Capacitors can also go bad/dry up etc yet still show a reasonably good value but when ran at high frequency in switching power supplies they will have a totally different capacitance and they'll heat up due to increase resistance and so on.

So basically, an ESR meter is much more useful.

Now, cheap esr meters like Bob Parker's esr meter or ESRMicro or other esr meters you find on eBay for 20-40$ are not really "true" esr meters, but they use some method of determining the ESR that actually gives a close enough approximation of the capacitors' esr, one that's good enough to tell you if a capacitor is bad or not.
They're much more useful and I highly recommend you to get one.

If you want really accurate esr reading, you have to invest into a proper LCR meter with ESR function... which cost from about 180$ and up.

Most of the ones on the cheaper end only measure up to 10kHz but this is still quite a reasonable frequency and if a capacitor has a high esr at 10 khz, it's unlikely it will have better esr at 100kHz.