ABSTRACT
When ultrasonic flowmeters were first introduced in the 1950s and 1960s the process control industry had high expectations for them. The reason the image of ultrasonic flowmeters was rather tarnished for decades is that the complexity of the measurement produced was not realized initially. The flowmeter usually consists of an electronics housing, transducers, and a pipe section. The acoustic coupling to the pipe and the relative alignment of the transducers must be maintained in spite of pipe temperature changes and vibration, in order to obtain acceptable performance. As with transit-time flowmeters, in order to properly indicate volumetric flow, the pipe must always be full. The Doppler flowmeters will operate independent of pipe material provided the pipe is sonically conductive. One of the most promising tasks for smart ultrasonic flowmeters is to automatically evaluate the presence or absence of reflector particles or bubbles and to automatically switch from the transit-time to the Doppler reflection mode of operation and back.
