Panametrics, Inc.

General Electric Company

James M Korba

Lawrence C Lynnworth

Toan Huu Nguyen

Lei Sui

James E Matson

Saul A Jacobson

Generoso Polcaro

David R Wallace

A multimode flow meter can use both the time-of-transit of upstream and downstream ultrasonic signals and time for transmission of downstream-only signals to determine a flow velocity of a medium flowing through a conduit. Based on factors, such as previously computed flow velocity and signal-to-noise ratio of the upstream signal, a mode of operation may be switched and only the time for transmission of the downstream signals may be used to determine flow velocity. The multimode flow meter can compute cross-flow to reduce its effect on the determination of flow velocity.

Flow measuring device and method using transmission paths having different angles

A flow meter, or flow path intervalometer, transmits a transmission signal modulated with digital pseudo-noise or similar code. The received signal is correlated with the transmitted signal at successive times to produce a correlation function having a peak at a time to equal to the propagation time. The code is selected such that the side lobes of the correlation function are small. An interpolator determines a precise time of maximum correlation. In one embodiment, upstream and downstream correlation functions are defined and are correlated to determine an upstream-downstream propagation time difference interval .DELTA.t. In a preferred embodiment the digital code is a Barker code, and the transmitted signal is a finite interval wave which is phase modulated by the Barker code. In another embodiment, the received signal is a reflected signal which is range gated so as to represent flow data originating from a desired region within the conduit. The signal is sampled in phase quadrature and transformed to determine its frequency domain representation, and the devide derives local flow rate information from Doppler information. In yet another embodiment, a plurality of transducers are arranged to provide a number of sampling paths across the conduit, and the flow meter varies the range gating interval for the signal received along each path to derive a Doppler frequency, hence flow rate, for each of many sample intevals or bins along the path. The total flow in the conduit is then obtained by summing the flow in each bin times a cross-sectional area weighting factor.

Differential correlation analyzer

An intervalometer for determining the transit time of an ultrasonic energy pulse through a fluid medium employs an automatic gain control amplifier circuit for amplitude stabilizing the electrical signal derived at a receiving transducer. The automatic gain control circuit tracks both a rapidly increasing and a rapidly decreasing signal amplitude. In various embodiments, synchronous switching can be employed in conjunction with a single amplifier and a plurality of storage elements to rapidly scan a plurality of signal paths and for providing automatic gain control capability on each path. The intervalometer further has a 'slipped cycle' capability for accurately determining arrival time when is is known that the signal pulse will be within a certain range of times. In addition, the relative time difference between two arriving signal pulses can be accurately determined using this method so long as the range of time difference is sufficiently small. The intervalometer also provides for bad data rejection based upon limits applied to either transit time or signal amplitude.

Intervalometer time measurement apparatus and method

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Woburn, MA, United States of America

James M Korba