Dual path ultrasonic fluid flow metering system and method

TLDR: An ultrasonic fluid flow metering system for use in monitoring volumetric flow of fluids conveyed in conduits or open channels is described in this paper, where pulses are applied to the transducers and the transit time of the pulse energy through the fluid in two directions is utilized to generate frequencies which give an indication of the fluid flow.

Abstract: An ultrasonic fluid flow metering system for use in monitoring volumetric flow of fluids conveyed in conduits or open channels. The flow meter includes at least one pair of transducers which alternately operate as transmitters and receivers to propagate energy through the flowing medium between the transducers. Pulses are applied to the transducers and the transit time of the pulse energy through the fluid in the two directions is utilized to generate frequencies which give an indication of the fluid flow. The system includes means for generating pulses which are transmitted through the fluid in opposite directions and a voltage controlled oscillator, the output of which is divided and used to provide delayed output pulses. The delayed output pulses are compared in time phase to the received pulses transmitted through the fluid in the conduit or channel and the frequency of the oscillator is controlled to provide time coincidence between the compared pulses. A count of the VCO output pulses over a predetermined period is alternately performed for upstream and downstream transmissions and the difference in the count provides a measure of the fluid flow.