23-07-2011, 05:56 PM
Welcome to this enjoyable relaxed forum Marty!
Many of the ESR meters have been successfully built, and have proved useful, but if you have any difficulties, please don't hesitate to contact me, when I'll be happy to help in any way possible. In retrospect, I think my posting on the forum on this project may perhaps deter rather than to encourage people to build it, because in my desire to give the fullest information about how it evolved from the original design, based on feedback from constructors, there’s just such a heap of information that it may be off-putting. I hope not. The final design and layout of the PCB is much simplfied from the original, based on feedback from the less experienced construtors who had problems with the wiring of the front panel pot and the meter, sometimes getting the polarity wrong, and mixing up the connections to the pot. In the final version those problems have been eliminated by incorporating a pre-set pot on the PCB. Also, theres' provision for an LED if desired.
It's handy to have a scope at the testing stage, but by no means essential. If built carefully, it should work straight off, and the only adjustment needed is to set the pre-set pot to get full scale deflection on the meter with the cap test leads shorted. The meter scale works in a similar fashion to that of an Ohmmeter, in that full scale deflection is zero Ohms, and the further to the left the needle moves, the higher the effective series resistance of the cap under test, and the more suspect it becomes. 2 Ohms is about 75% FSD, 5 Ohms about 50%, and 10 Ohms about 25%. Generally, if I find anything much more than 5 Ohms, I compare the cap with a known good one. It's as well to try a few new caps to get the hang of what to expect. We're not looking for exact readings - just a low ESR. I know that many like to own precision test gear, but it simply isn't necessary to know that a cap has an ESR to four decimal places on a digital display to know whether the cap should be binned.
The meter I used is still available and in stock at the aptly named ESR Electronics at £5.54 + £2.50 P&P + VAT. Order Code: 124-116, description: 0-50µA Panel Meter.
http://www.esr.co.uk/electronics/product...tequip.htm
Hope these addtional comments are of help and interest.
Best of luck with the project!
David
Many of the ESR meters have been successfully built, and have proved useful, but if you have any difficulties, please don't hesitate to contact me, when I'll be happy to help in any way possible. In retrospect, I think my posting on the forum on this project may perhaps deter rather than to encourage people to build it, because in my desire to give the fullest information about how it evolved from the original design, based on feedback from constructors, there’s just such a heap of information that it may be off-putting. I hope not. The final design and layout of the PCB is much simplfied from the original, based on feedback from the less experienced construtors who had problems with the wiring of the front panel pot and the meter, sometimes getting the polarity wrong, and mixing up the connections to the pot. In the final version those problems have been eliminated by incorporating a pre-set pot on the PCB. Also, theres' provision for an LED if desired.
It's handy to have a scope at the testing stage, but by no means essential. If built carefully, it should work straight off, and the only adjustment needed is to set the pre-set pot to get full scale deflection on the meter with the cap test leads shorted. The meter scale works in a similar fashion to that of an Ohmmeter, in that full scale deflection is zero Ohms, and the further to the left the needle moves, the higher the effective series resistance of the cap under test, and the more suspect it becomes. 2 Ohms is about 75% FSD, 5 Ohms about 50%, and 10 Ohms about 25%. Generally, if I find anything much more than 5 Ohms, I compare the cap with a known good one. It's as well to try a few new caps to get the hang of what to expect. We're not looking for exact readings - just a low ESR. I know that many like to own precision test gear, but it simply isn't necessary to know that a cap has an ESR to four decimal places on a digital display to know whether the cap should be binned.
The meter I used is still available and in stock at the aptly named ESR Electronics at £5.54 + £2.50 P&P + VAT. Order Code: 124-116, description: 0-50µA Panel Meter.
http://www.esr.co.uk/electronics/product...tequip.htm
Hope these addtional comments are of help and interest.
Best of luck with the project!
David
