Patent ID: 7690266

Claim:
An apparatus for measuring at least a speed of sound (SOS) in a process flow in a conduit, the apparatus comprising: first and second transducers positioned on the conduit at an axial position and circumferentially spaced apart from each other and generating ultrasonic signals, wherein the relative positions of the transducers is such that said signals emitted from each transducer interfere with each other to generate, sub-ultrasonic acoustic input signals in the process flow over a range of frequencies; a plurality of strain sensors on the conduit, spaced from each other around the cross-sectional circumference of the conduit, which strain sensors are adapted to sense strain associated with the sub-ultrasonic acoustic input signals and produce strain signals; and a SOS processor adapted to receive the strain signals, and configured to identify peak strains associated with cross-mode frequencies of the conduit and to produce using the peak strains associated with the cross-mode frequencies a signal indicative of the SOS in the process flow.