BEHA UNITEST CHB 10, Инструкция по эксплуатации, Страница: 26 / 48

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4.7 True RMS measurements / Crest factor
(only Clamp Meter CHB 35 )
True RMS measuremets
Commonly availa b le clamp meter s give an average value, and are
therefore only s uita b le for mea s uring DC, and pure s ine-wave AC
current s and voltage s .
If the AC current or voltage i s not a true s ine-wave, for example
due to di s tortion from a pha s e controller, then true RM S mea s ure-
ment s mu s t b e made – with the UNITEST Clamp Meter CHB 35 ,
they can b e.
Ta b le 1, b elow, s how s a compari s on of mea s urement s made with
the UNITEST Clamp Meter CHB 35 , and tho s e made with conven-
tional clamp meter s that have average and peak value function s :
Crest factor:
The cre s t factor i s the ratio of the peak value to the RM S value of
a s ignal.
Thi s i s important for RM S mea s urement s ( UNITEST Clamp Meter
CHB 35 ). Although the mea s ured value may lie within the cho s en
range, if the peak value of the s ignal i s too high, the UNITEST
Clamp Meter CHB 35 may b e overmodulated and give fal s e rea-
ding s .
4.8 MIN/MAX and peak values
The MIN/MAX b utton can b e u s ed to find either the large s t or the
s malle s t value of a s erie s of mea s urement s . Pre ss ing the MIN/MAX
b utton activate s fir s t the MIN mode, s o that the s malle s t value i s
s elected. Pre ss ing it a s econd time change s to MAX mode, for the
large s t value. Pre ss ing the b utton a third time return s the in s trument
to normal operation.
Wave form
RM S value
Rectified value
Di s play UNITE S T
Clamp Meter
CHB 15
Di s play UNITE S T
Clamp Meter
CHB 35
Deviation
Deviation
PTDB93468-05.qxd 14.12.2005 9:41 Uhr Seite 26