Ultrasonic system for measuring flow rate, fluid velocity, and pipe diameter based upon time periods

An ultrasonic flowmeter using ultrasonic pulses transmitted within a pipe containing flowing fluid determines values, including flow rate or fluid velocity of the flowing fluid. The ultrasonic flowmeter transmits trains of ultrasonic pulses having velocity components either in the upstream or downstream direction. The ultrasonic flowmeter includes the transducer placed downstream external to the pipe and a transducer placed upstream external to the pipe. Time measurements are made to determine a time, TU, required for a pulse train to travel from the downstream transducer to the upstream transducer and the time, TD, required for a pulse train to travel from the upstream transducer to the downstream transducer. The ultrasonic flowmeter is configured to have consistent triggering of the pulses of the pulse train to reduce error. Also, the electronics are simplified to allow for lower timing resolution requirements. Once TU and TD are determined, a series of validation filters, parameter filters, coarse flow filters, and refined flow rate filters are used to determine flow measurement. Alternatively, fluid velocity filters are used. Also, diameter filters are used to determine the current interior diameter of the pipe. All measurements are made noninvasively. The system and method includes determining coefficients for the various filters to account for variability in dimensions, parameters and conditions involved.