GW Instek GDM-8246 User Manual - Manual (Page 14)

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6-3. AC+DC measurement
A signal includes an ac component and a dc level. The relationship
between the total rms value of the signal and the ac component and the
dc component is:
rms total= 2 2 component) (dc rms) component c ( + a
6-4. Crest factor
Crest factor is often overlooked in determining the accuracy of an ac
measurement. Crest factor is defined as the ratio of the peak signal
amplitude to the rms value of the signal.
If an input signal has a crest factor of 3.0 or less, voltage
measurements will not be in error due to dynamic range limitations at
full-scale.
The waveforms in Figure 6-2 show signals with increasing value of
crest factor. As you can see from the series of waveforms, a signal with
a crest factor above 3.0 is unusual.
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z Figure 6-2: Crest Factor