METHOD AND APPARATUS FOR FLOW MEASUREMENT WITH TEMPERATURE AND DENSITY COMPENSATION

摘要

A transit time ultrasonic flow meter (40) includes a pair of ultrasonic transducers (44, 46) transmitting an ultrasonic signal through a fluid (48) flowing in a conduit (50) and receiving the transmitted ultrasonic signal. A comparator then detects a difference in phase between the received ultrasonic signal and a reference signal having a selected phase shift with respect to the transmitted ultrasonic signal. Control circuitry (52) selects the phase shift of the reference signal based on outputs of the XOR phase comparator in order to maintain the phase shifts detected by the XOR phase comparator. Since the outputs of the phase comparator are correlated to fluid flow, adjusting the phase of the reference signal enhances the inventive flow meter's measurement of fluid flow.