Abstract: A method and device (60) is described which measures the speed of a flowing fluid (F) by measuring the difference in time taken for an ultrasonic signal to travel first upstream and then downstream in the fluid. In each direction the device (60) calculates the time taken for an ultrasonic wave packet emitted by one ultrasonic transducer (62) to be received by another (63). The method used consists of the digitisation (85) of the received waveform and the subsequent identification of waveform features by comparison with a standard template of the waveform. The position in time of these features is then determined with respect to a high speed clock (70). The results are then used in a weighted computation to determine the time of arrival of the waveform at the transducer (63).

Abstract: The present invention relates to a fluid flow arrangement where the effects of high order acoustic modes are suppressed in ultrasonic flow measurement. In one embodiment, ultrasonic transducers are arranged in a duct configured to carry a fluid. Ultrasonic signals between the transducers travel in a plurality of high order modes having velocities slower than a fundamental mode whose time of flight is desired to determine with accuracy. A measurement portion between the transducers is adapted to suppress the propagation of the non-fundamental modes.

Abstract: A fluid meter has a central cylindrical section in which time-of-flight ultrasonic measurements can be made between acoustic transducers disposed in spaced apart enlarged end sections. The central section has a smaller diameter than do the end sections. Transitional regions join the end sections to the central cylindrical section. The transducers are located at least in part in the transitional regions. The transitional regions in the intermediate central section are generally shaped such that in combination with the shape and location of the transducers, pressure drops along the central section along with back-reflections of acoustic pulses from the transitional regions are reduced.

Abstract: Disclosed is a method and apparatus with which errors caused by the propagation of high order accoustic modes in ultrsonic flow measurement are reduced. Accoustic wave packets are transmitted between two transducers (1,2) arranged in a duct (3). A ringaround transmission technique is used and implemented by a control device (4) in which every fourth wave packet is inverted with respect to the preceding packets in order to annul the propagation effects of high order modes in the duct (3). This permits increased accuracy in the detection of reception of the wave packets by the transducers (1,2) enabling increased accuracy in flow velocity measurment.

Abstract: Ultrasonic piezoelectric transducer comprising a piezoelectric material having a profile whereby the transducer transmits and/or receives ultrasonic vibrations in a dilational (quasilongitudinal) mode. The profile is curved and includes a point of inflection. Possesses a vibrational peak in the frequency range 10 KHz-200 KHz. Construction is performed via profiling and tensioning the piezoelectric material.