GB372521A - Improvements in electro-optic control system - Google Patents

Abstract

372,521. Thermostats. COMMUNICATION PATENTS, Inc., 60, Broadway, New York, U.S.A. April 15, 1931, No. 11138. Convention date, July 24, 1930. [Class 64 (ii).] Optical interference bands falling upon photo-electric cells are used for measuring or controlling temperature or other physical quantities. Light from a source 5, Fig. 1, is reflected from a surface 10 which is liable to displacement due to thermal expansion or other cause. By the semi-reflector 8 and lens 20 interference bands are projected on to a photoelectric cell 21 having two cathodes 22, 23. Displacement of the surface 10 causes displacement -of the interference bands so that one cathode, for example 22, becomes operative. A current impulse passes through the impulse counter 30 which registers it, disables the valve 26 and counter 35, and enables the oscillator 40 to generate oscillations in the coil 17. These act on the magnetic body 12 associated with the reflector 10, so as to annul the latter's displacement. Displacement in the opposite direction actuates the amplifier 26, counter 35 and oscillator 46, and disables the parts 25, 30, 40, so that coil 16 becomes effective instead of coil 17. As applied to the thermostatic control of a piezo-electric crystal, the crystal 86, Fig. 3, on expanding or contracting with temperature moves the reflecting surface 77 and so displaces the interference bands, projected from the semi-reflecting surface 76, on to the photo-cells 102, 103. One or other of the cells (according to the direction of displacement) becomes active and causes oscillations to pass from the oscillator amplifier 94 to one or other of the transformers 89, 90, which are associated with rectifiers 91, 92. Thus current passes in one direction or the other through thermo-couples 79, which heat or cool the crystal 86 by means of the Peltier effect and so restore the original temperature.