On 7/8/19 10:47 AM, Bob Engelhardt wrote:
If I measure a full wave voltage with a non true-RMS common variety
DMM*, will it be off by a known factor, from the true RMS value?

Or is there a rule of thumb about the error.Â* E.g., the reading will be
high by about 10%.

Thanks,
Bob

* - Extech Ex320 if it matters

Depends. If it reads the peaks, it'll be high by a factor of sqrt(2).

If it reads the mean, it'll read 2/pi times the peak value, which is low
by a factor 2*sqrt(2)/pi = 0.9003. So 10% is right in that case,
except that it would read low.

Of course it could do some random third thing instead.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com