Abstract: An ultrasonic transducer includes a film of piezoelectric material mounted on the support column. Two overlapping metal foil electrodes are in intimate contact with the two opposite surfaces of the film respectively, and a respective electrical lead is connected to each electrode.

Abstract: An apparatus for measuring the speed of an air flow comprises an ultrasonic transmitter and an ultrasonic detector mounted spaced apart on a housing for insertion in the air flow. A circuit inside the housing derives the speed of the air flow as a function of the time taken for the burst to reach the detector.

Abstract: From a first aspect this invention provides a missing pulse detector for determining the true termination time of a sequence of pulses in a signal of an assumed predetermined length having a rising edge and a trailing edge which may include pulses which do not reach a predetermined threshold, the detector including a counter connected to count pulses exceeding said threshold, up to a predetermined number, an oscillator for producing pulses at twice the frequency of the pulses in the signal and an enabling circuit for allowing pulses from the oscillator to pass to the counter only after the termination of a sequence of threshold-exceeding pulses from the signal.

Abstract: A distance sensing apparatus is provided in the form of a case housing electronic equipment including a piezoelectric transducer for radiating pulsed sonic or ultrasonic signals along a measurement path through a sound horn (3) which creates a narrow beam. Reflected signals received back through the horn are received by the transducer and converted into electric measurement signals. A time measurement device is providing for determining the time lapse between radiation of a pulse and receipt of a reflected signal so as to provide a distance signal which will be representative of the path distance between the apparatus and the surface which will trigger a display (7) to give a distance reading.