GW Instek PCS-1000 - Manual (Page 29)

OPERATION
29
Crest Factor Table
Crest factor is the ratio of the peak signal amplitude to the RMS
value of the signal. It determines the accuracy of AC measurement.
If the crest factor is less than 3.0, voltage measurement will not
result in error due to dynamic range limitations at full scale.
If the crest factor is more than 3.0, it usually indicates an abnormal
waveform as seen from the below table.
Waveform Shape Crest factor
Square wave 1.0
Sine wave 1.414
Triangle sawtooth 1.732
Mixed frequencies 1.414 ~ 2.0
SCR output 100% ~
10%
1.414 ~ 3.0
White noise 3.0 ~ 4.0
AC Coupled pulse train >3.0
Spike >9.0