Measurement Computing WavePort 312P rev.1.0 User Manual
Page 63

PowerVista/312 User’s Manual
Spectrum Analyzer 7-3
V. We could include more frequencies left and right of the signal, but in real life those frequencies will contain
information unrelated to our signal in addition to our spread signal.
After a Hamming Window is applied, the resultant spectrum appears as shown in
Figure 7-3.
Notice here that
the peak value is 194.64 V at 695.8 Hz. The peak magnitude is reduced slightly. The total RMS energy
however, has been concentrated around this center frequency instead of spread left and right and tapering off as
in
Figure 7-2.
For this case, there are four values that contain this concentration, and they are listed in Table 9.
The root sum square of these values is 249.79 V, which is an excellent approximation to our applied signal of
250 V RMS. The resultant error is less than 0.1%.
Table 8. 700 Hz Spectral Results with no Hamming.
Frequency
Value
Value Squared
634.7656
13.44
180.88
646.9727
16.45
270.61
659.1797
21.27
452.56
671.3867
30.24
914.82
683.5938
52.84
2792.93
695.8008
204.34
41755.66
708.0078
106.84
11415.61
720.2148
41.81
1748.09
732.4219
26.05
679.06
744.6289
18.88
356.66
Total:
60566.93
Square Root of Total:
246.10
Table 9. 700 Hz Spectral Results with Hamming.
Frequency
Value
Value Squared
683.5938
40.30
1624.09
695.8008
194.64
37884.34
708.0078
150.74
22723.75
720.2148
12.67
160.50
Total:
62392.68
Square Root of
Total:
249.78