| Measurement and Signal Processing | |
(iii) Preventation of leakage by coinciding periods :
As discussed above, we can obtain the correct result if the time duration measured coincides with the integer multiple of the period of the original signal. If we can attain this by some means, it is better than the use of window functions, which distorts the original signal. For example, for numerical calculations that can be repeated in exactly the same way and whose sampling interval can be adjusted freely, we can determine the measurement duration after we know the period of the original signal by trial simulation, and then execute the actual numerical simulation. On the contrary, for experiments, fine adjustment of sampling intervals is generally impossible using practical measuring instruments. However, if the phenomenon appears within a speed range, we can change the rotational speed little by little and adopt the best result where the period, often determined by the rotational speed, and the sampling interval fit. |
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