PURPOSE: To provide a device which ensures accurate correction of delayed time without any special delay time element provided in the time detection circuit by setting between the total propagation time and the propagation time in the fluid to be measured while putting a specified value at the deviding ratio preset for the divider.
CONSTITUTION: As illustrated, an ultrasonic flowmeter is equipped with a pair of ultrasonic vibrators 12 and 13 for transmitting or receiving ultrasonic wave propagating the intended fluid flowing through a pipeline 100 (13 one receiving side in the drawing), a divider 4, a phase comparator 5 for comparing the phase between the signal received with the receiving vibrator 12 and the output signal of the devider 4 and an oscillators 8 and 9 adapted to oscillate with the received frequency and provide an output to the divider 4. The dividing ratio N preset for the divider 4 is determined by the formula herein given and the delay in time is set based on the total propagation time obtained from a quotient between the dividing ratio of the divider 4 and the frequency of the oscillators 8 and 9 and the actual propagation time in the fluid to be measured. The flow speed of the fluid is measured from the difference in the frequency of the oscillators 8 and 9 in the normal and opposite direction with respect to the fluid. Thus, accurate correction of the delay time is possible without any special delay time element.
WASHIMI TETSUO
UEMATSU MAKOTO
