GB598176A - Improvements in or relating to temperature-sensitive instruments - Google Patents

Abstract

598,176. Measuring sounds and like vibrations. ACE ELECTRONICS, Ltd., WELCH, L. C., and COOK, R. J. Nov. 24, 1944, No. 23448. [Class 40 (i)] [Also in Group XX] A temperature indicator utilizing mechanical waves comprises a cathode-ray oscillograph arranged to indicate the phase difference between electrical oscillations supplied to and received from two electro-mechanical transducers attached, in spaced relation, to a rigid body. (e.g. a rod or tube) subject to the temperature to be measured, whereby mechanical waves pass from the transmitter to the receiver through the body or through a liquid medium contained therein. As shown, the magneto-strictive or piezo-electric transducer 1, oscillated at resonance by the generator 12, sends vibrations through the body, whose temperature is to be measured, to a receiving transducer 2 (of equal resonance), whence corresponding electric oscillations are applied, through a phase-maintaining amplifier 13 and a phase-splitter 21, to the deflecting electrodes of a cathode-ray tube 14, thus causing the spot to rotate in a circular path in phase with the received vibrations. The oscillations of the generator 12 are also applied to the cathode-ray tube through the path 16, 17, 18 (the latter converting the sinusoidal oscillations a into sharp pulses b, one per cycle) to cause radial deflection of the spot, the angular position of which around the trace will coincide with the phase displacement angle and when read against a suitable scale on the screen will indicate the temperature. The transducers may have a resonance of, e.g. 10 mc., in which case the electric oscillations corresponding to the emitted and received signals may be reduced to a frequency of the order of 1 kc., by heterodyning in the mixer-modulators 16, 19 with the output from an oscillator 15, maintained at a frequency of 1 kc. above that of the generator 12 by heterodyning the latter in a mixer-modulator 25 with the output of a 1 kc. oscillator 26. Tuned filter circuits 17, 20, 24 eliminate unwanted frequencies. A suitable temperature-sensitive unit (Fig. 1, not shown) may comprise a metal tube filled with water or butyl bromide, the ends of which are closed by the two crystals 1, 2 pressed against a fluidtight packing by spring contacts held in place by insulating screw caps. A small maintaining reservoir partially filled with air may be connected to the tube. According to the Provisional Specification, a single transducer may be used for emission and reception from an internal reflecting surface of the body, and a regulating device may be controlled by a signal produced by a thermionic valve in dependence upon the phase relation of the emitted and received oscillations.