Analog ultrasonic flowmeter

Abstract

A meter for measuring the velocity of a fluid by ascertaining propagation periods of acoustic wave packets transmitted therein, the meter including a pair of transducers for disposition in the fluid, a transmitter for transmitting a packet between the transducers in an upstream or downstream direction designated by an up/down signal at each time designated by a transmit signal and a receiver for developing a received signal marking the time of receipt by a transducer of each packet, the times being marked so as to avoid amplitude and half-cycle ambiguity errors. The meter also includes a phase detector for comparing the received times with those marked by a reference signal to develop early and late pulses, a decoder and a pair of integrators for developing from the pulses a pair of integrated signals representing changes in the upstream and downstream propagation periods, another integrator for combining the integrated signals to develop a signal representing the acoustic velocity of the fluid and an amplifier for combining the integrated signals to develop a signal representing the velocity of the fluid. Further, the meter includes a ramp generator for developing the up/down signal, a ramp signal and the transmit signal from the acoustic velocity signal and the combination of a multiplexer, a multiplier and a comparator for developing the reference signal, the multiplier for developing a signal inversely proportional to the acoustic velocity signal and multiplying it by a signal developed by multiplexing the integrated signals.