Ultrasonic flow meter using mode coupling transducers

This paper describes the development of an ultrasonic flow meter using a new type of transducer called the mode coupling transducer (MCT). The mode coupling transducer consists of a thin plate of a suitable piezoelectric material on which an interdigital transducer (IDT) is deposited for the generation and detection of plate acoustic waves. The flow meter consists of two such transducers mounted on opposite walls of a pipe through which the fluid is flowing. The transducers used in this work were fabricated on 0.5 mm thick plates of lithium niobate and had a center frequency of 1 MHz. The prototype device developed here can measure flow rates over a range from less than 0.2 lpm (liters per minute) to greater than 100 lpm.