[volt-nuts] Fluke 720A Kelvin Varley Divider Questions

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sun Sep 19 21:17:51 UTC 2010

Charles P. Steinmetz wrote:
> Bill wrote:
>> You're kidding, right ?
> I've never used one, and I'd be interested to know what you (and 
> others) think its failings are.
> Best regards,
> Charles
A more general question would be:

Is it possible to design a chopper stabilised null detector using modern 
components with a performance equivalent to the 845A?

Whilst the noise of most chopper stabilised opamps is much larger than 
that of the 845A, perhaps something like the approach used in:
could be used.

Since the low noise preamp is AC coupled a lower noise input using a 
single ended JFET could be substituted for the one using the LSK389.


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