| 摘要 |
<p>PURPOSE:To regulate the turning-off time of the turning-on and off control to a constant time even for a low control set temperature, by providing a generating circuit for the forced conduction command of the heater circuit in the electric heater. CONSTITUTION:AC power source 1 is connected to heater 2 through relay contact 11a, and further, power of power source 1 is converted to a constant-voltage DC power source in 5 and is divided in 6 and is supplied to thermosensitive resistor 3. The impedance change of resistor 3 accompanied with the temperature change of heater 2 is detected by detector 7. This detection value is compared with a prescribed threshold by switching circuit 8 and is decided, and relay 11 is controlled to switch contact 11a. Generating circuit 12 for the forced conduction command of the heater circuit is provided in circuit 8. Circuit 12 is provided with clock circuit 14 and counter 13, and counter 13 is driven in accordance with the cut-off output of the heater feed line of comparing circuit 9 of circuit 8; and when counter 13 counts a prescribed number of clocks of circuit 14, the signal corresponding to closing of contact 11a is given to the input of circuit 9 forcedly, thus regulating the turning-off time of contact 11a to a constant time.</p> |
