| 摘要 |
PURPOSE:To impart the highly accurate wire breakage detecting function to a temperature detecting circuit wherein a thermistor is used by a simple circuit, by providing a means for detecting the polarity of the terminal voltage of a resistor which is connected to the thermistor in a bridge in series. CONSTITUTION:A first detecting means 7, which detects the variation in resistance value of the thermistor 1, is provided in the bridge circuit whose one side is the thermistor 1. Bias resistors 6 and 8 are provided between both ends of the resistor 2 which is connected to the thermistor 1 and a power source 5. In this temperature detecting circuit, a second detecting means 9, which detects the polarity of the terminal voltage of the resistor 2, is provided. For example, the circuit as shown by the Figure, wherein an open collector type comparator is used as the detecting means 7 and 9, is used. When the output of the comparator is ''L'', it is regarded that the temperature is higher than the upper limit, or the thermistor wire 1 might be broken, and heating is not performed. |
