Patent ID: 7117104

Claim:
A method of determining a rate of flow of a fluid in a conduit, the method comprising acts of: sending first and second ultrasonic signals along a length of the conduit using a pair of ring-shaped transducers disposed at first and second positions spaced apart along the length of the conduit; receiving the first and second ultrasonic signals; cross-correlating the first received ultrasonic signal and the second received ultrasonic signal to generate a resulting time-domain signal; analyzing the resulting time-domain signal to determine a difference in transit time between the first received ultrasonic signal and the second received ultrasonic signal; calculating the rate of flow of the fluid in the conduit based upon the determined difference; and providing the calculated rate to another device for use as the determined rate of flow of fluid in the conduit; wherein the act of cross-correlating comprises: performing a Fourier transform on the first received ultrasonic signal to generate a first frequency-domain representation; performing a Hilbert transform and a Fourier transform on the second received ultrasonic signal to generate a second frequency-domain representation; multiplying the first and second frequency-domain representations together to generate a resulting frequency-domain representation; and performing an inverse Fourier transform on the resulting frequency-domain representation to generate the resulting time-domain signal.