| 摘要 |
PURPOSE:To make measurement of frequencies possible without receiving the in fluence of noise and amplitude change by calculating the time when an input sine wave signal zero-crosses by using a circuit analysis method and taking the inverse number of the period thereof. CONSTITUTION:A sample holding circuit 1 sample-holds the amplitude analog value at each point of time of an input sine wave signal according to the sampling pulses outputted from a timing circuit 4 based on clock pulses and applies the value thereof as amplitude information to an operator 3. A counter 2 calculates time data by counting the clock pulses and applies this to the operator 3. Based on these data, the operator 3 makes circuit analysis, thereby determining the period of the sine wave signal. The period determined by this is taken of reciprocal by the circuit of the subsequent stage, whereby the frequency of the sine wave signal is determined. Thereby, the highly accurate frequency measurement is accomplished without being affected by noise and the change of amplitude. |
