"Shaun"

I used to work at an Industrial and Instrumentation repair and Calibration
shop that was licensed by Beckman to repair and calibrate there DMMs. In
the good ones, the RMS converted used a thermal method to determine RMS
Voltage and Current. That was 18 years ago and I don't remember any
details except that they used thermal measurement on a heated element. I
have compared the reading on the Beckman - Then Wavetek - now I don't know
if anyone is still making them, to a Fluke RMS DMM at 60 Hz and DC and the
readings matched.

** No fooling...........

I have always heard that if you really want to know the real value, you
have to buy an RMS meter.

** That sort of nonsense *would* be said by someone who either owned an RMS
meter or was selling them.

Thermal RMS meters are virtually obsolete these days and have been replaced
by cheap analogue RMS to DC computation ICs in many hand held DMMs OR by
digital sampling computation in most DSOs.

The hand held kind have a limited measurement bandwidth compared to the
latter.

Depends what your needs are.

As Clint Eastwood might have said -

" Man's gotta know the limitations of his test equipment ".




..... Phil