[volt-nuts] Poll

Andreas Jahn Andreas_-_Jahn at t-online.de
Wed Sep 15 21:32:56 UTC 2010

> Basically, the circuit, battery and/or AC power supplies, and all 
> connections to
> such would be floating (except "earth" grounding) from the outside 
> container.
> The outside container would be tied only to the "earth" connection of the 
> AC
> power cord and/or any separate external "earth" connection that you may 
> provide.
> It is most instructive to study the Fluke 335D construction and circuitry. 
> This
> instrument demonstrates the proper way regarding "guarding" and "leakage." 
> Other
> "guarding" worth reviewing is the Fluke 731 and 732 reference supplies as 
> they
> also provided such processes.
> Bill....WB6BNQ

Hello Bill,

Thanks a lot for the informative hints:

I had a look at the Fluke 335D manual. So I think that against the Fluke
I am missing at least one shield (or even two since the inner shield does
not cover all cirquitry) in my planned construction.

I have only a outer metal case around all cirquitry including batteries
and voltage stabilisation

and a inner metal shield around the LTZ1000 cirquit including resistors.

The only thing that I eventually wanted to do is to connect some
filtering capacitors (1 to 5 nF) from the output terminals
(and the stabilized voltagte) to the inner shield.
I hoped this would work for a battery supplied reference when
removing 24V charger connection. But for shure I have some
improvement capabilities for the next build.

Something which I cannot get clear from the manual is the exact position
of the "Guard" and "Chassis" shield against the "Case".

The "Case" seems to be the outer tube around the Instrument.
But how is the front-panel constructed. If the  3 shieldings had to be 
I would need 3 isolated front panels. The outer connected to "Case".
The next inner connected to "Guard" and the 3rd as part of the "Chassis".

Best regards


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