| 摘要 |
PURPOSE:To detect easily the disconnection, etc. of a detecting element, by switching successively the resistance value of the voltage dividing resistance which is in series to a detecting element like a thermistor, etc. having its resistance value varying in response to the state by means of a switching means and then discriminating the level by the resistance value. CONSTITUTION:The detected voltage corresponding to the temperature due to a voltage dividing circuit 20 provided with a thermistor 1 having its resistance varying in response to the rise of temperature and series resistances 8-11 is compared with the divided reference voltage obtained by resistances 6 and 7 through a comparator 2. Then the temperature is detected by a processing circuit 3. At the same time, the voltage dividing points of the resistances 8-11 are connected to switching transistor 12-14. These transistors are turned on and off successively in rsponse to the frequency of the control signal given from the circuit 3. Thus the disconnection which causes an increment of the resistance of the thermistor 1 is detected easily and assuredly on the basis of the output of the comparator obtained in an on-state and via the circuit 3. In the same way, it is possible to detect a fault, etc. of the comparator 2. |
