Humidity sensor using temperature sensing resistor controlled to be at constant temperature of more than 150.degree. C.
US5837884A · kind A · utility
Assignees
Inventors
Key dates
| Filing date | Aug 23, 1996 |
| Grant date | Nov 17, 1998 |
| Priority date | — |
| Expiry date | Aug 23, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N27/18
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A humidity sensor of a heat conduction type which enables a humidity measurement to be produced by a single temperature sensing resistor so as to reduce a change in characteristic depending on a temperature change of the measurement atmosphere and to reduce the cost, comprises a temperature sensing resistor 1 and three fixed resistors R.sub.1, R.sub.2 and R.sub.3 which form a Wheatstone bridge circuit. The humidity is measured by utilizing the fact that the heat dissipation of the temperature sensing resistor 1 changes depending on the humidity. The temperature sensing resistor 1 is heated by a heat generator 2 for self-radiation of Joule heat so that the temperature of the temperature sensing resistor 1 is controlled to be at a constant temperature of 150.degree. C. or more. The output voltage value of the Wheatstone bridge circuit is corrected with reference to the variation of the output voltage value depending on the ambient temperature of the temperature sensing resistor 1.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.