Patent ID: 7201065

Claim:
A sensor for measuring fluid flow in a pipe having a pipe axis, the sensor comprising at least two pairs of acoustic transducers disposed on at least one probe having a respective probe axis and insertable into the pipe to a respective probe insertion depth, each probe having a respective flow measurement direction transverse to the respective probe axis, each pair of the transducers associated with a second pair of the transducers, each pair of the transducers arranged to transmit and receive respective oppositely directed acoustic signals transverse to the respective flow measurement direction along a respective quasi-helical path having an opposite rotational direction from the quasi-helical path of that other pair of transducers with which said each pair is associated; the sensor further comprising signal processing circuitry for processing the acoustic signals from the at least two pairs of transducers to determine respective transit-times associated with each pair of transducers, for adding the transit-times of associated pairs to cancel effects of a rotary component of the flow and for providing a respective raw flow signal value representative of a component of the fluid flow along the respective flow measurement direction.