Improvements in or relating to electric circuits for controlling the supply of current to a load impedance

摘要

908,813. Automatic temperature-control systems. GENERAL ELECTRIC CO. Ltd. Oct. 26, 1960 [Oct. 30, 1959], No. 36915/59. Class 38 (4). [Also in Group XL (c)] Automatic control of the temperature of a crystal oven is effected by a circuit shown in Fig. 1 in which resistor 17 is sensitive to the temperature in the oven and resistor 8 is the oven heater winding. Transistors 2 and 3 form a bi-stable circuit controlled by a comparator circuit 1, 4 in which the voltage across the temperature-dependent resistor 17 is compared with the voltage at the terminal of potentiometer 15, 16. Thus, the heater winding 8 is energized by the bi-stable circuit depending on whether the resistor 17 is above or below the predetermined temperature. A resistor sensitive to the ambient temperature of the circuit may be connected in series with resistor 18 to compensate for temperature changes.