| 摘要 |
PURPOSE:To detect frequencies up to about 1/10 as high as the sampling frequency of an input signal from a direct current with high accuracy by changing detecting means according to the sampling frequency and frequency range of the input signal. CONSTITUTION:The voltage of a system 1 is stepped down to a signal level by a potential transformer 2 to obtain the input signal. Then, the input signal inputted to an analog input card 3 is sampled at a specific sampling frequency and also A/D-converted before being inputted to a microprocessor 4. Then, sampling data are processed by a microprocessor 4 to obtain the frequency of the input signal, which is displayed numerically on a display device 6 through a digital output card 5. Thus, frequencies up to about 1/10 as high as the sampling frequency are detected with high accuracy from the direct current at a relatively low frequency, e.g. a sampling frequency of order about 10 times as high as a frequency to be detected.
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