measurements...

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: davep <davep-at-quik-dot-com> 

(This is from a professional power quality mag.
I thought it might be illustrative as to the difficulties
and detail level in doing 'accurate/mwaningful'
measurements.)
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In the article you reference, the expression "total effective" as used with 
current or voltage relates to the calculation of power losses through a 
system resistance. This value is also useful in determining loading on 
thermal circuit breakers. The rms values, when used to calculate losses, 
will give the real losses in watts, and the rms currents will indicate the 
real load on circuit components. Any "true rms" meter from a reputable 
manufacturer should give the desired values.

Having said that, there are subtle differences in meters of which you 
should be aware. When selecting a meter to be used for measuring current or 
voltage in a system serving loads with switched-mode power supplies, the 
maximum crest factor (the ratio of peak to rms values) that the meter can 
be exposed to and still read correctly will determine whether the "true 
rms" value actually captures all the harmonics. Some inexpensive meters 
state that they can handle crest factors of 2 or 2.5. Since the crest 
factor of computer power supplies is usually between 3.5 and 4, this type 
of meter will not provide readings that represent the "true rms" value.

In general, if you select a "true rms" meter from a reputable manufacturer 
and make sure that the meter can handle high enough crest factors, you can 
feel confident that, for power calculations and loading values, the meter 
will show you the "total effective" current or voltage.
================================================
PS:
If its not been mentioned the book
	Empires of Light
discusses, Tesla, Edison, Westinghouse and the war
of the currents.  While not strictly ad rem this list,
and like no follow up, it may be of interest.

-- 
	best
	dwp

.