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Measurement Computing WavePort 312P rev.1.0 User Manual

Page 63

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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