Abstract: A flow measurement system including at least first and second ultrasonic transducers coupled to an existing conduit, a damping material about the conduit between the first and second ultrasonic transducers to prevent crosstalk, a damping material about the conduit upstream of the first ultrasonic transducer to attenuate system background noise travelling in the conduit at large, and a damping material about the conduit downstream of the second ultrasonic transducer to attenuate system background noise travelling in the conduit at large.

Abstract: A clamp-on ultrasonic measurement system for a gas or other fluid typically of low acoustic impedance such as low pressure steam or flare gas. The system includes a first ultrasonic signal transducer which clamps to the conduit, and a second ultrasonic signal transducer clamped on the conduit across from the first transducer. Each transducer is operated to transmit to, and receive from, the other along contrapropagation signal paths. The transducers generate a shear wave signal that skips within the conduit wall to coherently energize a region of the wall and launch ultrasonic signal energy at a defined angle across the direction of flow. The receiver is symmetrically arranged and positioned to respond to signal energy received along the path through the fluid.

Abstract: An apparatus and method for measuring gas flow velocity through a high stack employs ultrasonic transducers. The transducers are placed on opposite ends of a diameter several hundred feet up, with a small vertical separation L between the transducers. Apparatus for measuring acoustic velocity in the stack gas over short path lengths is also included.

Abstract: An acoustic burst with a predetermined amplitude envelope is triggered by a square wave signal and transmitted upstream or downstream to a transducer connected to an adaptive control system which tracks the midpoint of the received envelope. The received signal is rectified and fed via a polarity reversing circuit controlled by the square wave to an integrator whose output level controls the frequency of the square wave. The burst transit time is measured to the next zero crossing of the received signal following the half cycle transition point of the square wave.

Abstract: An ultrasonic system that measures either the impedance of a fluid or liquid level utilizes moderately directional, bulk SV mode sound waves generated by a transducer and propagated in a homogeneous, flaw-free solid member. The SV wave propagates in the solid along a zigzag path that reflects at a solid-fluid interface in at least two areas and at an angle of incidence that exceeds the first critical angle by at least five degrees and is less than the second critical angle by at least ten degrees. The attenuated amplitude of the wave due to acoustic coupling between the solid and the fluid measures the impedance or an impedance related parameter of the fluid. The system preferably includes a second acoustic path that serves as a reference to compensate for changes in parameters such as temperature, the nature of the fluid, the transducer, the transducer coupling, and residues or corrosion at the solid-fluid interface.

Abstract: An ultrasonic flowmeter for determining fluid flow velocity within a conduit by determining the difference in transit time between interrogating ultrasonic pulses transmitted upstream between a pair of transducers and transmitted downstream between them. A high frequency clock pulse operating for one or more cycles of interrogation allows for accurate digital computation.

Abstract: In the acoustic flowmeter apparatus disclosed herein, repetitively gated bursts of relatively high frequency acoustic energy are transmitted between upstream and downstream transducers in a conduit in which flow is to be measured, the transmission being alternately in an upstream and a downstream direction. The received signals are amplified and subjected to narrow band filtering so as to extract an essentially continuous component at the high frequency, preserving phase information. By measuring the relative phase shifts of the upstream and downstream transmissions, a measurement proportional to flow rate is obtained. In the preferred embodiment, the sum of the transit times is measured by measuring the phase shifts of the principal repetition frequency modulation component of the received signals.