| 摘要 |
PURPOSE:To enhance the measuring accuracy of all time intervals by accurately measuring even a time below one pulse without increasing the frequency of a clock pulse, by utilizing a time interval expanding circuit. CONSTITUTION:When a transmitting pulse P and a receiving pulse R are inputted to an FF circuit 1, the FF circuit 1 is turned ON only between pulses P, R. The output of the circuit 1 and a clock pulse are applied to an AND gate circuit 3 and an increment counter 4 counts the number A of arrival clock pulses and a time difference detection circuit 9 detects a pulse turned ON only between times t1, t2 from the risings of the pulses P, R to that of the clock pulse respectively succeeding to said pulses P, R. The output of the circuit 9 is digitalized at an expanding ratio m-times the time t1, t2 by an A/D converter 8 through an integration circuit 7. Then, the output of the converter 8 and that of the circuit 1 are applied to a subtractor 5 and digital numerical values B, C corresponding to the time mt1 and the time mt2 are calculated. Hereupon, the value of the time interval (t) between transmission and reception is calculated according to formula t=[A+(B-C)/m]X(time corresponding to one wavelength of clock). |
