Control circuit using a sulphonated fluorocarbon humidity sensor
US5014908A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 27, 1989 |
| Grant date | May 14, 1991 |
| Priority date | — |
| Expiry date | Nov 27, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N27/225
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A control circuit (1) for use in a humidifier (H). A capacitor functioning as a humidity sensor (55) includes a sulphonated fluorocarbon material acting as the dielectric (57) of the capacitor. The material is sandwiched between sheets (59a, 59b) of a screen material which act as plates of the capacitor. An RC oscillator (53) has a variable frequency output and incorporates the capacitor. Changes in the dielectric value of the material due to sensed changes in humidity produce changes in the oscillator output frequency. A DC voltage is supplied to the oscillator. The amount of voltage impressed on the sensor at relatively high-humidity levels is controlled to prevent leakage currents caused when the material is exposed thereto. The generation of such leakage currents otherwise adversely effects sensor operation. Operation of the circuit to control operation of the humidifier is also described.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.