PERIOD MEASURING INSTRUMENT, FREQUENCY MEASURING INSTRUMENT, PERIOD AND FREQUENCY MEASURING METHOD, AND METER DRIVING DEVICE

摘要

PURPOSE: To suppress the occurrence of beats, rounding errors, and DC errors by calculating the weighted averages of the variation of the period and frequency of input signals and including the calculated averages in measured output period and frequency values. ;CONSTITUTION: An adder 38 supplies the weighted average T_n+1 of the counted results T_in of a binary counter 16 and a period T_n latched by a register 18 at timing (n) to a drive device, etc. At the time of supplying the average T_n+1, the period T_n is inputted to the A-input of an adder 42 and to the B-input of the adder 42 after inverting the period T_n by means of an inverter 40. In addition, the higher-rank (m) bits of the B-input of the adder 42 are fixed at a value '1' and the output terminal of the inverter 40 is connected to the B-input by shifting the output terminal rightward by (m) bits. Therefore, the data of the B-input become -2^-mT_n and the output of the adder 42 becomes the sum (1-2^-m)T_n of both A- and B-inputs. The adder 38 outputs the weighted average T_n+1=(1-2^-m)T_n+T_in. The occurrence of rounding errors and DC errors is suppressed by smoothing and averaging the variation of count values in such way. In addition, similar measurement can be performed about the frequency by finding the inverse F_in of the output T_in of the counter 16.;COPYRIGHT: (C)1993,JPO&Japio