Crest Factor (C.f.); True Rms Measurement / Crest Factor - Unitest CHB 5 Bedienungsanleitung

5.7

Crest Factor (C.F.)

1) Turn selector switch (3) to "~mA, ~A oder ~V"
2) Select basic frequency via switch(10).
3) Select "C.F." vie key FUNC (6)
4) at ~mA and A measurement
1) Open the clamp, and close it round the conductor. Make sure that the clamp
properly encircles the conductor, and that there is no air gap between the
jaws. For best measurement results and highest accuracy, have the conduc-
tor placed in center of clamp jaws.
at ~V measurement
1) Plug the black test lead into the "COM" socket and the red lead into the "VΩ"
socket
2) Connect the probes to the UUT and read the display
The crest factor (CF) is defined as following: CF = (peak value / RMS value)
5.8

True RMS Measurement / Crest Factor

True RMS Measurement:
Conventional current clamps indicate the mean value and, therefore, are only ap-
propriate for DC currents/voltages and pure sinus-shaped AC currents/voltages.
If the AC current/voltage is not sinus-shaped, e.g. caused by distortions due to a
phase control, a true RMS measurement must be carried out. The UNITEST clamp
CHB 5 is suitable for true RMS measurement. The table shows the comparison bet-
ween the UNITEST clamp CHB 5 with true RMS measurement and current clamps
with mean value and peak value sampling.
Crest Factor
The crest factor or peak factor indicates the ratio between peak value and true RMS
of a signal. This unit finds particular attention with true RMS measurement instru-
ments (UNITEST Clamp CHB 5). Although the measurement value is located within
the selected measurement range, the UNITEST Clamp CHB 5 could be amplified and
supply faulty measurement results, if the signal to be measured shows excessive
peak values.
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