Measurement Computing WavePort 312P rev.1.0 - 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