| 摘要 |
<p>1,225,302. Automatic temperature control systems. SIEMENS-ELECTROGERATE G.m.b.H. May 6, 1968 [May 5, 1967; Sept. 27, 1967], No.21439/68. Heading G3R. An electric heating element 1 e.g. in a hotplate is supplied through bi-metal switch 3-5 the heater of which is controlled by a threshold value switch e.g. a thyristor or breakdown diode so that when the temperature sensed e.g. by a thermistor 7 rises to a value set by a corresponding resistor 8, the threshold switch conducts hence causing the bi-metal switch to open. In an alternative arrangement Fig.2 (not shown), components 3, 7, 8, are arranged in a bridge network together with an added resistor 12. In a further arrangement Fig. 3 (not shown) the control circuit is fed from a tap on the heating element and the bi-metal heater is controlled by a transistor threshold value amplifier. In Fig. 4 (not shown) a diode is used a threshold value device controlling heater current to a reed relay (40, 42) and in Fig. 5 (not shown) a complementary pair of transistors (29, 34) are rendered conductive at the determined temperature with a lag of 90 degrees each half cycle, but in an alternative arrangement the lag may be reduced to zero by including an R. C. member (45) in the circuit.</p> |
