[Collins] Bucking Voltage -AC Line voltage

[Dr. Gerald N. Johnson, electrical engineer]

That is a problem. The Simpson and the VoltOhmist are both sensitive to
waveform and are adjustable. They are peak reading calibrated in RMS.
Any waveform distortion will change their readings. The panel meters may
be true RMS or peak reading calibrated in RMS but generally aren't
adjustable. But their rectifiers (including that in the Simpson 260) may
have been affected by age.

Meter repair shops do have standard meters for comparison. I've also
collected a university surplus 1% tolerance lab meter for reference, but
I generally depend on a 3-3/4 digit digital meter that actually does a
true RMS analog computation and use the Simpsons and VTVM as indicators
of presence or absence rather than for precision readings. One hopes
that the newest digital meter reads closer, but its easy for it to be
peak reading calibrated in RMS. 

I guess, I'd believe the highest reading panel meter and adjust the
others to match. I believe that panel meter aging will tend to make it
read lower rather than higher. But, I'd rather have a standard meter or
voltage source known to have low distortion.

Gerald
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