Fluid flow monitoring

Abstract

A method and an apparatus for (a) monitoring fluid flow by transmitting acoustic signals in opposite directions through a fluid with components in the direction of flow; (b) receiving the transmitted signals; (c) providing a first signal representing acoustic velocity; (d) time-integrating the first signal to produce a ramp signal, the rate of change of which represents acoustic velocity in the fluid; (e) transmitting a first acoustic signal in one direction through a fluid; (f) transmitting a second acoustic signal in the opposite direction through the fluid; and (g) initiating integration of the first signal. The ramp signal is compared with a second signal representing fluid flow velocity to generate first and second arrival signals according to the direction of the transmitted acoustic signal; expected arrival times for the transmitted acoustic signals are compared with the actual arrival times of the transmitted acoustic signals, and the results of the comparisons are stored. The stored results from two successive acoustic signal transmissions are then compared so as to either modify the first signal, if both acoustic signals arrived earlier or later than their respective expected arrival times, or to modify the second signal, if one acoustic signal arrived before, and the other after their respective expected arrival times.