Improvements in temperature control systems

摘要

641,615. Automatic temperature control systems. BRITISH THERMOSTAT CO., Ltd. Dec. 3, 1947, No. 31944. [Class 38 (iv)] [Also in Group XXXVI] In a temperature control system employing a Wheatstone bridge circuit 1 the unbalanced output of which regulates a heater or cooler 9 to restore the temperature to a predetermined value, two supplementary or anticipatory temperature-sensitive resistances 11, 11a disposed in close relation, are connected in adjacent sides of the bridge so that they do not normally influence the balance. The resistance 11 responds directly to the surrounding temperature, whereas the resistance 11a is arranged to respond to this temperature only after a predetermined time lag. Thus, for air flowing in a duct 10 past the heater 9 to a chamber 3, the heater is initially controlled by the resistance 11 but after the time lag when the resistance of 11a becomes equal to that of 11 the control is passed to the main control element 2. An anticipatory effect may be obtained by placing the resistances 11, 11a before the heater (Fig. 2, not shown). The time lag of resistance 11a is made adjustable by variable vents in the shroud 12 of the resistance (Fig. 3, not shown), (see Group XXXVI).