Water-absorbing capacitor system for measuring relative humidity
US4662220A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jun 20, 1985 |
| Grant date | May 5, 1987 |
| Priority date | — |
| Expiry date | Jun 20, 2005 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N27/225
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method and apparatus using a known water-absorbent polymer as a capacitor which is operated at a DC voltage for measuring relative humidity. When formed as a layer between porous electrically-conductive electrodes and operated in an RC oscillator circuit, the oscillator frequency varies inversely with the partial pressure of the moisture to be measured. In a preferred embodiment, the capacitor is formed form Nafion and is operated at a low DC voltage with a resistor as an RC circuit in an RC oscillator. At the low voltage, the leakage current is proper for oscillation over a satisfactory range. The frequency of oscillation varies in an essentially linear fashion with relative humidity which is represented by the moisture being absorbed into the Nafion. The oscillation frequency is detected by a frequency detector.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.