J&w Scientific Incorporated

Curtin Matheson Scientific, Inc.

William Stephen Woodward

An acoustic displacement flowmeter determines the flow rate of a fluid in a path containing a controllable valve by establishing fluid flow along the path, directing the flow of the fluid to a transducer having a displacement element by restricting the flow path, generating a signal from the transducer representative of displacement due to fluid flow while the flow path is restricted, using the transducer to determine the fluid flow rate, and reestablishing fluid flow along the path by removing the restriction. The transducer signal is used to determine the fluid flow rate by providing an analog reference signal, integrating the analog reference signal for a predetermined time period, deintegrating the integrated reference signal with the transducer signal until the value of the deintegration signal reaches a threshold value, and using the time required for the deintegration signal to reach the threshold value to calculate the flow rate. The time is accumulated by counting the number N of fundamental sampling periods occurring during the deintegration of the integrated reference signal and determining the flow rate from the equation V=A/N-B, where V is the mass flow rate and A and B are constants. A temperature correction signal for adjusting the calculated flow rate value for temperature variations is generated by providing first and second sensor signals whose ratio is representative of temperature, integrating the first sensor signal for a predetermined time period, deintegrating the integrated first signal with the second sensor signal until the value of the deintegration signal reaches zero, and using the time required for the deintegration sensor signal to reach zero to calculate the temperature correction signal.

Acoustic displacement flowmeter

Fluid flow along a fluid path is determined by measuring the travel time between two transducers of two oppositely travelling acoustic burst waves. A pair of phase reference signals in phase quadrature are compared with the signals received by each transducer to determine the phase difference therebetween. The phase difference values are used to calculate the flow velocity. After each phase difference determination has been made, the transducer drive signals are adjusted so that the launch time of the next pair of burst waves reduces the phase difference between the previously received signals and the phase reference to zero in the absence of any changes in flow velocity. The duration of each acoustic burst is sufficient to ensure that a predetermined number of successively received cycles in each burst are used in the phase comparison process.

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Chapel Hill, NC, United States of America

William Stephen Woodward