GB1003985A - Apparatus for testing an ultrasonic transducer - Google Patents

Abstract

1,003,985. Photo-electric indicating devices. UNITED BRISTOL HOSPITALS. July 24, 1963 [July 24, 1962], No.28410/62. Heading G1A. [Also in Division H4] In an arrangement for measuring the intensity of the radiation produced by an ultrasonic transducer the radiation from the latter 10, (Fig. 1) which is immersed in a water filled tank 12, is directed by reflection at 16 towards a radiationpressure sensitive member 18 carried by an arm 24 mounted on the moving coil 20 of a moving coil instrument 22. Movement of arm 24 caused by radiation pressure on member 18 is arranged to vary the amount of light falling on a photo-transistor 30 (Fig. 2) which together with a second phototransistor 32 subjected to constant light from the same source (Fig. 3, not shown) form two arms of a bridge circuit the output of which is supplied via a D.C. transistor amplifier 48 to one side of the coil 20 and other side of which is supplied from a D. C. source of opposite polarity via a circuit including a milliampermeter 52. Thus, as the bridge goes out of balance due to movement of arm 24, the output of transistor 48 is reduced and current flows via the circuit including milliampermeter 52 which acts to rotate coil 20 in a direction which returns the arm 24 (and member 18) to the initial position. The current indicated by meter 52 is thus a measure of the radiation pressure and this may be determined directly by suitable calibration. In the well position the member 18 is arranged to hang with a slight inclination to the vertical in order to avoid errors due to buoyancy forces caused by bubbles sticking to it and to reduce the effect of standing waves This inclination may be set by adjustment of potentiometer 60 which thus allows compensation to be effected for departure from the horizontal of the surface on which the instrument rests.