Sampling theory, in conjunction wit

Sampling theory, in conjunction with the Nyquist criterion, enables you toreduce the sampling rate from 500 Hz to 50 Hz. Applying a filter anddownsampling the data set reduces the number of samples in and thecomputational complexity of the data set. The goal is to use as few samplesas possible to evaluate the behavior of the system.Sampling theory enables you to downsample, or decimate, the data set.Downsampling reduces the sampling rate, 500 Hz, by a factor of 10. Thusdownsampling enables you to acquire the data at a sampling rate of 50 Hz.The Nyquist criterion states that you need to sample the signal at aminimum of twice the highest frequency in the system.Recall that the input data is equally spaced over the frequency band0.122–24.4 Hz. Therefore, according to the Nyquist criterion, you need tosample at a minimum of 50 Hz to avoid any antialiasing. The benefit ofsampling at 50 Hz is that you still acquire all the data in the frequency band,yet you eliminate the resonance peak at 42 Hz.Therefore, in Figure 9-7, the SI Lowpass Filter VI sets the cutofffrequency to 25. In addition to applying a lowpass filter to the data, youmust downsample the reduced data set. The SI Down Sample VI inFigure 9-7 uses a decimation factor of 10.