TRANSDUCTEURS ET APPAREIL LES CONTENANT

摘要

1361052 Automatic control of liquid level RADUN CONTROLS Ltd 3 July 1972 [9 July 1971] 32422/71 Heading G3R [Also in Division H4] A transducer head for sensing the presence of liquid comprises a body having a pair of limbs with a gap between them, two Piezo-electric elements mounted on respective ones of the limbs so as to face each other across the gap, and an oscillator and detector amplifier mounted on the body and connected to respective ones of the elements whereby an amplifier output signal in response to vibrations transmitted across the gap occurs only if liquid is present in the gap. In the Fig.1A embodiment the transducer head is a generally cylindrical stainless steel member 2 slotted at its end 3 to define two limbs in which Piezo-electric discs Tx, Rx are mounted in plugged bores 7. Ultrasonic vibrations transmitted across the slot by disc Tx are received by disc Rx whose output amplitude is compared with a reference signal to derive an error signal. For liquid level sensing, this error signal drives a motor to winch the head up or down to maintain it immersed a given amount in the liquid. For liquid level control the error signal actuates a pump or valve to introduce liquid into or withdraw it from a container. The head may alternatively be arranged to respond to liquid flowing over it. One or more heads each giving an "on-off" type signal may be arranged at fixed heights within a container.