Blue ESR understanding table

[DavidOH]

I'm having a little trouble understanding the table on this. I've downloaded two other tables to compair. For example I have two caps 50v 22uf. One reads 1.3. The other reads 2.1. If I understand this right the 2.1 is bad and the 1.3 is a little high but okay. The cap reading 1.3 goes next to a 450v 22uf cap reading .72 which I think is also okay. Then again I may be way off.

Other tables I downloaded.

http://members.ozemail.com.au/~bobpar/2003esrchart.txt

http://www.jestineyong.com/esr-meter-table/

[mariushm]

Re: Blue ESR understanding table

The table is from 2003, it's a bit outdated.

They're some approximate values he calculated, based on whatever capacitors were on the market back then. Since then, capacitor technology has evolved and the caps are much better made these days.

Capacitors above 100uF should nowadays have an ESR value lower than 0.3 ohm... below 100uF, it really varies on the voltage and can size (diameter+height).

Above about 330uF, good capacitors should have less than 0.25 ohm esr, depending on voltage (16v and up should be < 0.10-0.15 ohm)

For example, I have a 2.2uF 400v capacitor that has 11 ohm esr and that's OK, but I also have a 4.7 uF 400v capacitor that's 5 ohm ESR.

For a 22uF 50v capacitor, I would find 1.3 ohm reasonable, but for one that reads 2.1 ohm, I'd be a bit concerned. It also depends on the can size, if it's a miniature capacitor the 2.1 ohm would be OK in my book.

A relatively standard (compared to today's standards) Nichicon PW capacitor would have about 1.2 ohm esr at 22uF/50v.

[DavidOH]

Re: Blue ESR understanding table

Is there an updated table I can use? I have another 50v 22uf that reads .78. These are small caps. I'll get this figured out somehow.

[LDSisHere]

Re: Blue ESR understanding table

What I do is use the impedance rating from the datasheet as a guide to approximate what the ESR reading should test. This may not be a perfect solution but it will at least give you an idea if it is bad or not if you can find the datasheet. Also if you have two identical caps (brand, series, ratings, etc.) and they give you different readings of any significance then one or both are most likely bad.

[budm]

Re: Blue ESR understanding table

Get yourself a couple PANASONIC FM/FR series each (values that you use often) and use them as the ref. caps, that may be good enough if you put in the PANASONIC and it fixes the problem.

[DavidOH]

Re: Blue ESR understanding table

Good info. Thanks