| 摘要 |
PURPOSE:To control the temp. of an electrical heating element so as to maintain a specified value with good accuracy by controlling the impedance of a variable impedance body incorporated into a bridge circuit so as to make zero the unbalance voltage of the bridge circuit. CONSTITUTION:The resistance value of the electrical heating element 16 increases with an increase in the temp. of the element 16 when said element is heated. This temp. is affected by not only the current value supplied to the element 16 but also the ambient temp. and the moisture contained in a heat developable sensitive material. However, the resistance value R of the element 16 and the heating temp. T of the heat developable sensitive material correspond one to one and the heating temp. of the heat developable sensitive material can be maintained constant by controlling the resistance value of the element 16 so as to maintain the specified value. The resistors Rgamma and RF correspond consequently one to one if the gate of an FET18 is so controlled as to make zero the unbalance voltage of the bridge circuit.
|
