Chapter 3
DMM Operation
©
National Instruments Corporation
3-7
DAQMeter DAQCard-4050 User Manual
Crest Factor
The DAQCard-4050 is calibrated to optimize the accuracy of measuring
sine wave inputs. Because the DAQCard-4050 uses the RMS method of
the AC measurements, it can also accurately measure inputs other than
sine waves. The accuracy of these measurements depends on the crest
factor of the input signal. The crest factor of a signal is the ratio of the
peak value of the signal to the RMS value of the signal. For example, a
symmetrical square wave has a crest factor of 1 and an undistorted sine
wave has a crest factor of 1.4. The DAQCard-4050 can measure signals
with crest factors of up to 10.
Table 3-4 shows the additional errors associated with different crest
factors.
Table 3-3.
Input Frequency Error Rate
Input
Frequency
Additional Error
(Percent of Full Scale)
20–50 Hz
2%
50–100 Hz
1%
100 Hz–5 kHz
0%
5–10 kHz
1%
10–25 kHz
2%
Table 3-4.
Crest Factor Error Rate
Crest
Factor
Additional Error
(Percent of Full Scale)
1–2
no error
2–5
1%
5–10
2%