| 摘要 |
PURPOSE:To improve a measuring precision at a high humidity region and to prevent thermal breakdown of a humidity-sensitive element due to overheating, by a method wherein a humidity measurement takes place in a condition to heat the humidity-sensitive element to a given temperature, and the cleaning temperature for the humidity-sensitive element is maintained at a constant temperature. CONSTITUTION:A humidity-sensitive element 4' is constituted such that a porous humidity-sensitive substance r, made of sintered metal oxide, is placed in a manner to cover a resistance wire acting as a core. A bridge circuit consists of a resistance R1 of the resistance wire, and fixed resistances R2, R3, and R4, while the potential change of the bridge circuit is inputted to an amplifier 5, and a current I is fed back to the bridge circuit from the output, which allows the temperature of the resistance R1 to be maintained at a constant temperature. As a result, the humidity- sensitive element 4' is also kept at a constant temperature, and thereby a change in a resistance value suitable for an equivalently low humidity range is shown even if a relative humidity at a measuring time is within a high humidity region. When the humidity-sensitive element 4' is cleaned, a resistance R5 is connected in parallel to the resistance R3 to bring the bridge circuit into a different balancing state, and impurities in the humidity-sensitive element is incinerated at a constant temperature. |
