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From: koziarz@halibut.nosc.mil (Walter A. Koziarz)
Newsgroups: sci.electronics
Subject: TRUE RMS Voltmeters WAS: Re: Powerline voltage too high, power co working on it
Message-ID: <3298@nosc.NOSC.MIL>
Date: 26 Dec 90 18:56:13 GMT
References: <2470004@hp-vcd.HP.COM> <9798@as0c.sei.cmu.edu>
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In article <9798@as0c.sei.cmu.edu> rsd@sei.cmu.edu (Richard S D'Ippolito) writes:
>Just got around to seeing this, and I'm sure you're quoting me --  anyway,
>no, the typical meter (analog or digital) is average responding, RMS
>equivalent reading.  Peak-reading meters are very rare and specialized.
>
no argument here; but.....

>Again, there is NO SUCH THING as "true RMS"; it's just RMS!
>
most likely the difficulty is semantics; *most*, typical 'AC' voltmeters do
read (either via analog meter or didgits) a value REPORTED TO BE RMS.  This is
'okay' as long as the INPUT IS SINUSOIDAL.  A 'True RMS' meter will display a
reading based upon the heating effect of the input voltage and is, therefore
capable of measuring non-sinusoidal voltages and reporting an RMS reading.

Walt K.



>Sorry to shout!
>
>Rich