Here's a few hints to help you get more from your ESR meter - MK 1 or MK II

(1) The way to hold the 9V alkaline battery in place is to lay it in the bottom of the case, then place a suitable-sized piece of thick foam plastic over it. Then the circuit board will hold it snugly in place when the front panel is screwed down.

(2) The "Approximate worst ESR values" table on the front of the meter were taken from a fairly old capacitor catalog(ue), and capacitor technology has evolved a bit since then. Many 105 degree C electrolytics have an ESR up to nearly double those values even when brand new, and other electrolytics have a lower ESR even when old. From my experience if an electrolytic has an ESR more than double the table value for its capacitance and voltage rating, it's wise to check it against a new one and/or replace it to remove the chance of it causing problems in the future.

Hank Sievers said, "Bob Parker's meter can also be used as a go-no go type. I have found that I can consider everything below 3 ohms as good, and all over 10 as bad, with very few falling in the doubtful category". I agree that except for very large and very small caps, this is a useful 'rule of thumb'. Thanks, Hank!

(3) The 'DISCHARGE CAPACITOR BEFORE MEASURING!' warning on the meter front panel is a little over-cautious.... 'Test only discharged capacitors!' would have been better. Nearly all electrolytics are discharged by their surrounding circuitry within a few seconds of the power being disconnected, so you can generally poke around with the meter without worrying about this. The only caps which are likely to need deliberate discharging are the main filters in amplifiers and other large power supplies.

(4) Glenn Watkins has pointed out that a shorted or partially shorted cap can check OK (ie: low resistance), so if you check a cap and the indicated ESR seems too good = low to be true, it's wise to check it out with an ohm meter.

(5) The meter puts out regular bursts of 10us pulses at a 2KHz rate, at an open-circuit amplitude of about 600mV P-P. At a pinch you can use it as an audio signal source to check speakers, amplifiers etc. The pulses have a fast rise/fall time, so it would probably make a crude RF signal injector as well. Thanks to 'Kiwi' Joe Lussy for suggesting this!

(6) Glenn Watkins also said, "It's very hard to press the test lead tips together to get a steady reading before pressing the button to zero the display. I found that if the test leads have sharp tips, you can press them both on a solder pad (on a PC board) and the leads will penetrate the solder a little giving a good solid reading". Thanks Glenn!

(7) We all know that varying contact resistance between the banana plugs and sockets can cause unsteady readings, but if you give each plug a big squirt of CRC "CO Contact Cleaner" then rapidly insert and withdraw it in its socket a lot of times, this reduces the problem considerably.

(8) A few techs have suggested that the test lead sockets should have the industry standard 3/4" spacing. When I was designing the meter I tried to achieve this, but unfortunately the plastic mounting pillars in the case are too close together to make it possible, while still leaving room for the push button switch. Sorry about that, guys.

(9) This is more of a note than a hint... The ESR meter kits are now coming out with Zilog Z86E0412PSC microcontroller ICs rather than the Z86E0408PSC referred to in the paperwork. The new chips are functionally identical to the earlier ones, the only difference being that they are rated for a higher crystal frequency- irrelevant in this circuit.


Finally a big "THANK YOU" to all you techs who've bought this meter and said good things about (and constructively criticised) it, both on the Sci.Electronics.Repair newsgroup and to me by e-mail. I really appreciate it!

Accolades section...

From walterh@xxx.com Mon Jul 27 16:53:17 1998
> Well an ESR meter measures the Equivalent Series Resistance of a
> capacitor. ESR means how well a capacitor passes AC while blocking 
> the DC, and the lower the ESR the better.

FWIW, I've had good luck using my ESR meter to debug hum problems in audio
circuitry, where the difference between ground and a few tenths of an ohm
to ground can mean an induced voltage.

    --Walter Harley -