| 摘要 |
<p>The capacitor monitoring circuit for measuring for example humidity, comprises a voltage driving circuit (22) providing two varying voltages (20, 21) of opposite phase, a first measuring circuit supplied with one of the voltages and including a first resistance (Ra) and a fixed capacitor (Cf), and a second measuring circuit supplied with the other of the voltages and including a second resistance (Rb) and a variable, humidity sensitive, capacitor (Ch). The resistances (Ra, Rb) are of generally the same magnitude and the capacitors (Cf) are of the different capacitive values. An adjustable resistance (Rx) is connected to one of the measuring circuits to provide null calibration at output (25) to a load (31), such as a meter. </p> |
