[volt-nuts] Fluke 720A Kelvin Varley Divider Questions
gbusg at comcast.net
Mon Sep 20 02:01:37 UTC 2010
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.
Good question/suggestion Bruce.
Maybe that approach could be used to re-design the first "half" of a HP
419A, building a modern circuit into an existing HP 419A to save time/money
and to come up with a nice little box that works well. (The HP 419A *was* a
small form-factor, cute, attractive instrument, with built-in supply &
batteries, so it might yet still have a use?)
I think the 419A can be purchased for practically nothing, if it can still
be found. ...again, I'm afraid many of them have already gone to graveyards
for scrap metal recovery.
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