I did a quick simulation of 1000uf with 0.030 ohm ESR. Waveform attached. The source is again a plus and minus 4v square wave, and the added series resistance for the test was 600 ohms.
Hi dr pepper,Hi Willen,
Theres little diffrence between the ludens schematic and the one you posted, in fact the ludens one has less parts, the osc and the amp are in one 8 pin chip, not having a transistor theres little in the way of biasing resistors.
The scale on mine starts at 30 ohm, going to 2 ohms 1/2 way, and the last quater way is 1 ohm, so you can read down to a fraction of an ohm, the only thing with a log scale is that you couldnt resolve 10 ohm from 10.5 ohm, however its more than acceptable for repair work, I dont read resistance the diffrence between a good and bad cap is usually large, tens of ohms.
This is certainly a simple method with a scope.
The Step voltage is a result of the ESR in the Cap, which in this case is 0.4V out of 4.0V pp or 10% and thus 10% of 600 Ohms or 60 Ohms.
Using the ESR*C figure of merit, this cap is 1000u*60 = 60ms which is a good result. ( 1ms best... 1 second is poor)
My attention to units failed.
step change on output 0.4mV ?? my mistake
step input = 4V
Rs= 600 Ohms
step attenuation = 4V/0.4mV = 10,000
if you add both input current steps + and -
then you have to add both output steps.
So dont.
So you input is only a 4V step not 8V
And my mistake output scale was mV
ESR = 600/10,000 = 60 mΩ
did I get it right this time?
That looks like a good design Nige, what did you use for the bulb?, I used to have some ra53 thermistors which were pretty much exclusively for wien osc's, but they've all long gone.
I only use CPC, RS and Farnell, and sometimes ebay.
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