[sdiy] expo accuracy? or integrator accuracy?, or both?

[René Schmitz]

Hi Martin, Ian and List!

At 12:38 10.02.03 +0100, Czech Martin wrote:

>The result was that the 30pA of the 
>3140 I used outweigh any other leakage source by far.

But did it have a reset switch? 

I am not surprised that the capacitor leakage is lower than 
the input bias. This is what I would expect from a foil cap. 

I remember a method in which you use a 10cm piece of RG 58 
as a low-value low-leakage capacitor to measure the bias 
current. That idea could also be used to measure the 
gate-source leakage of the reset jFET. With that it should 
be possible to dissect the individual leakage currents 
I mentioned earlier.

>I did not clean the circuit board, it was cheap paper/resin type,
>pre drilled. Surprise to me.
>Of course, this does not say anything about long term
>behaviour, moisture etc.
>But I have the feeling that board/soldering effects can
>be neglected in the 1pA range. Certainly not in the 1fA
>range which is perhaps not so interesting here.

Right. I'm also thinking that the effects of the flux are 
somewhat overestimated. I don't know about the american brands, 
but the stuff sold here by alpha metals seems pretty ok in that 
respect.

Cheers,
 René




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uzs159 at uni-bonn.de
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