Digital flow meter circuit and method for measuring flow

摘要

In a method and apparatus for generating a signal proportional to flow in a pipe using probes strapped onto the exterior of the pipe, two ultrasonic pulse trains at a carrier frequency are sent in opposite directions from one probe to the other. Two lower frequency signals are extracted from the two respective pulse trains and analyzed to detect a phase difference. The phase difference corresponds to a difference in the travel times for the two pulse trains caused by the flow velocity in the pipe. The two lower frequency signals are converted to digital data samples which are stored with reference timing data. A microelectronic processor synchronizes the two sampled waves, using the timing data, before comparing the sampled waves to determine the phase difference. The processor and associated circuitry also measure the travel times of the two ultrasonic pulse trains and generate an output signal proportional to flow based on the measured phase difference and the measured travel times.