Flow metering device based on the ultrasound principle with two oscillators

摘要

A flow metering device contains two ultrasound transducers (41, 43) in each case operating as a transmitter or receiver to which the frequency of one or the other oscillator (13, 15) can be supplied as desired by means of changeover devices (24, 45) when the direction of the ultrasound propagation changes. A counting circuit (61) emits an end-of-count signal (63) corresponding to the frequencies of the oscillators (13, 15) when a pre-defined counter reading is reached, while a control device (59) influences the frequency of the oscillators (13, 15) to the effect that a predefined relationship between the propagation time of the ultrasound waves (45, 47) and the counting time of the counting circuit (61) is maintained until the predefined counter reading is reached. To compensate for the effect of temperature changes, a device (81, 85) is provided to change the number N which is set in the counting circuit (61) according to the sum of the frequencies of the two oscillators (13, 15) in order to cause the latter to converge in a predefined range. <IMAGE>