| 摘要 |
PURPOSE:To measure a long time interval with high precision by utilizing a time interval extending circuit and measuring even the time of deviation from one wavelength of a clock pulse. CONSTITUTION:The Q outputs of FFs 1 and 2 which are set and reset by ultrasonic-wave transmitting and receiving pulses P and R go up to a high level during an ultrasonic-wave transmission time interval. An AND gate 4 is opened by the Q output of the FF1 and an up counter which counts a clock outputs a counted value A. The Q output of the FF2, on the other hand, increases by N times through the extending circuit 3 equipped with an integration circuit 3 to obtain an extended time interval from transmission to the next clock CK and an extended time interval from reception to the next clock CK, controlling the opening of an AND gate 5. An up/down counter 7 counts up and down the clock CK at the 1st and the 2nd opening time of this gate 5 and outputs a counted value B-C. A transmission-reception interval (t) based upon an equation I is measured from those counted values A and B regardless of clock wavelength to measure even a long time interval easily with high precision. |
