[volt-nuts] 731A output impedance

Bob Smither smither at c-c-i.com
Mon Nov 26 23:27:03 UTC 2012

The 731A is specified to have an output impedance of less than 1.1K in the 10V
setting.  A meter with 10 M input Z therefore causes a .01% (100 ppm) reading error.

I understand that when operated using a null meter the output impedance is not a
problem.  I would like to use my 731A as a bench standard for my DMMs.

The 10V output is taken through a 1K resistor (R18) from the output pin of the
op-amp.  Clearly the op-amp output pin is much lower impedance.

The op-amp is an LM301A and appears to be conservatively compensated.

I am thinking of shorting R18.  I understand it provides some protection to the
op-amp and may be a factor in the op-amp stability.

Other than the above, can anyone see why this would be a bad idea?

Bob Smither                                             smither at c-c-i.com
Circuit Concepts, Inc.                                       281-331-2744
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