| 摘要 |
1,226,015. Automatic temperature control systems. SIEMENS A.G. June 28, 1968 [July 1, 1967], No.31134/68. Heading G3R. An automatic control system, particularly for a diffusion furnace for semi-conductor doping having a proportional + integral action has the integral action suppressed or reduced during an increase of the rate of change of the error signal. A furnace 1 has the output from a detecting thermocouple 4 compared with a reference in a difference amplifier 5 the output from which is passed through a further amplifier 3 to control the firing angle of a thyristor unit 2 controlling heater current. Integral action is provided by a circuit R1, C the latter being shunted by a N. T. C. thermistor R2 heated by a separate resistor 9 fed from a differentiating circuit 6, so that when the rate of change of error signal is large thermistor R2 has a low value thus shunting capacitor C. In an alternative arrangement Fig. 4 (not shown) the capacitor C is shuntable by a contact of a relay energized from differentiating circuit 6. The contact may have a series resistor (18) to reduce the shunting action. The arrangement is stated to reduce overshoot in automatic control systems having a large time lag, and may be applied to controlled path drives in machine tools. The system may be applied to a mechanical control arrangement, Fig. 5 (not shown). |
