Apparatus for measuring propagation time of ultrasonic waves

摘要

In apparatus for measuring the propagation time of ultrasonic waves by counting the number of clock pulses occurring within the period of time from the transmission of an ultrasonic pulse to the receiving of the pulse, a receiving circuit receives a transmitted pulse and a received pulse and provides an output which continues from transmission until reception of the pulse. A time-difference detection circuit detects pulses occurring during a time interval t1 starting at the leading edge of the transmission pulse and ending at the leading edge of the first clock pulse thereafter and a time interval t2 starting at the leading edge of the received pulse and ending at the leading edge of the first clock pulse thereafter. The duration of the time interval t between transmission and reception is determined in accordance with the equation t=[A+1/m(B-C)]x (time corresponding to one clock wavelength) where B is a digital numeric value corresponding to the time interval mt; C is a digital numeric value corresponding to the time interval mt2 and m is the amplification ratio.