| 摘要 |
PROBLEM TO BE SOLVED: To provide a humidity sensor unit more inexpensively than before which is capable of performing a logarithmic compression and linear compensation. SOLUTION: A logarithmic compression circuit 7 includes two diodes D1a, D1b subjected to antiparallel connection and passes the current signal outputted from a humidity sensor 5 through the diodes D1a, D1b to convent the same to a logarithmically compressed voltage signal. A peak voltage holding circuit 9 outputs the peak voltage of the half-wave signal of one polarity of logarithmically compressed AC voltage and an output signal obtained by the temperature compensation of the peak voltage is amplified by an amplifier circuit 11 to be outputted from an impedance converter circuit 17. A compensation circuit 13 changes the bias voltage fed back to the logarithmic compression circuit 7 from a bias voltage generation circuit 15 corresponding to a change in the output voltage of the amplifier circuit 11 so that the reduction of the output of the amplifier circuit 11 as a function of relative humidity approaches linear reduction when the output voltage of the amplifier circuit 11 becomes a predetermined voltage or lower.
|
