| 摘要 |
PURPOSE:To obtain an inexpensive sensor circuit having a long lifetime by providing an analog switch in series to a humidity sensor to control the voltage impressed to the sensor. CONSTITUTION:The AC voltage of a sine wave, etc. is impressed to a humidity sensor 3 from an oscillation circuit 2 via a resistance 4. Then the humidity detection voltage is obtained at a juncture 20 and then supplied to a comparator 8 to be compared with the voltage value of a variable resistor 10 for set humidity. Thus a signal of H or L level is obtained and supplied to a controller 12 to control the working of an air conditioner, etc. An analog switch 13 is provided in series to the sensor 3 and turned on in a humidity measurement mode and off in a non-measurement mode respectively by the controller 12. Thus the lifetime of the humidity sensor circuit 3 can be increased since the output voltage of the circuit 2 is impressed to the circuit 3 since the switch 13 is turned on only in a measurement mode. |
