| 摘要 |
An absolute humidity meter in which a humidity sensor changes an electrical impedance thereof-exponentially with respect to the relative humidity. A z-f converting circuit (impedance to frequency ) generates a pulse signal corresponding to the impedance. A time constant control differentiating circuit has an impedance of a voltage control variable impedance element changed exponentially by a control voltage, and outputs a differentiated signal obtained by differentiating the pulse signal. A waveform shaping circuit outputs a pulse signal train obtained by binary-valued the differentiated signal. An integrating circuit causes a first integrating circuit to obtain the control voltage by integrating the pulse signal train and a second integrating circuit to obtain an output voltage of a relative humidity signal by integrating the pulse signal train, and obtains an absolute humidity signal by causing at least one of these integrating circuit to control the control voltage or the output voltage with increasing temperature.
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