[volt-nuts] Fluke 332D

[Bruce Griffiths]

It has to be inverting or the correction loop would be unstable.

The entire amplifier is configured as an inverting amplifier with the 
feedback resistors setting the gain and hence the output.
The chopper amp merely nulls the summing junction voltage by applying a 
correction to the noninverting input of the amp.
The feedback is only negative if the chopper amp is inverting.

Bruce

Dick wrote:
> Thanks, Bruce. Very helpful; still can't see it, tho'.
>
> Dick
>
>    
>> Message: 2
>> Date: Tue, 04 Dec 2012 22:47:56 +1300
>> From: Bruce Griffiths<bruce.griffiths at xtra.co.nz>
>> To: Discussion of precise voltage measurement<volt-nuts at febo.com>
>> Subject: Re: [volt-nuts] Fluke 332D
>> Message-ID:<50BDC6CC.4020808 at xtra.co.nz>
>> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>>
>> Dick wrote:
>>      
>>> I need a little circuit help here -- I'm looking at the schematic of the chopper amp, A5A4, and I'm trying to figure out if this amp is inverting or non-inverting for DC signals, that is from pin 6 input to pin 4 output. I'm looking at the simplified diagram on page 102 of the PDF manual, Fig 8-1, 3 of 3. The detailed circuit for the chopper is on page 104.
>>>
>>> Best,
>>> Dick Moore
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>>>        
>> Inverting.
>>
>> Bruce
>>      
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