| 摘要 |
PURPOSE:To eliminate the need for an oscillation circuit and to permit simplification, weight reduction and cost reduction of a circuit by coupling a DC power supply to a humidity sensor and controlling the on-action time and off-action time for the purpose of measurement by a timer. CONSTITUTION:One end of an ion conductive humidity sensor 1 is coupled to a + terminal of a DC power source 2 via a switch 3 and the other end thereof is grounded via a resistor 4 and is coupled to an output terminal 5. The timer 6 for controlling the on-action time within one second for the purpose of measuring humidity and the off-action time before the - ions accumulated in an anode are recovered at the time of measurement is coupled to the switch 3. The switch 3 is turned on by the on command from the timer 6 at the time of the humidity measurement, by which a DC voltage is impressed to the sensor and the voltage is detected at the output terminal 5. Since the resistance value of the humidity sensor 1 changes according to the humidity, the voltage to be detected at the terminal 5 changes with the humidity. This voltage eventually indicates the humidity.
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