| 摘要 |
<p>Apparatus for controlling humidity comprises a humidity sensing circuit including a humidity sensing element the electrostatic capacitance of which varies in accordance with the ambient relative humidity, and an air-conditioning system responsive to the sensed humidity. The humidity sensing element is charged and discharged repeatedly in accordance with a pulse train signal, and a period required for the voltage across the sensing element is measured during charging by a comparison between the voltage and a reference voltage. The pulse width or the reference voltage may be changed to select a desired reference humidity. A hysteresis characteristic may be given to render the operation of the circuit stable. When an SCR is controlled by the output signal of the humidity sensing circuit, the frequency of the pulse train signal is selected to be greater than four times the frequency of the voltage applied to the SCR.</p> |
