| 摘要 |
PURPOSE:To obtain a detector which produce a wide ranging frequency output and a sine wave output with limited distortion, by arranging a Wien bridge type oscillation circuit having two electric resistance type moisture sensors. CONSTITUTION:A moisture detection circuit comprises a difference input amplifier 1, capacitors 6 and 7, two electric resistance type moisture sensors 8 and 9 made of the same moisture sensing material for determining oscillation frequency and the like which form a Wien bridge type oscillation circuit. For example, the two sensors 8 and 9 are formed on the same substrate to vary the oscillation frequency by changing the resistance values of the sensors 8 and 9. Thus, a wide ranging frequency output and a sine wave output with limited distortion can be obtained regardless of about three-digit exponentially functional changes in the resistance values of the sensors 8 and 9 due to moisture and changes therein due to temperature and can be inputted direct into a microcomputer.
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