Chemical sensing apparatus and methods
US5512882A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 7, 1991 |
| Grant date | Apr 30, 1996 |
| Priority date | — |
| Expiry date | Aug 7, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N27/126
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Apparatus for the detection of a vapor of a selected chemical substance includes a sensor whose impedance changes upon exposure to such a vapor. The sensor comprises a polymer whose physical structure is altered by the vapor, e.g., through expansion or disintegration, and electrically conductive elements that are interspersed with or separated by the polymer. The interspersed elements may consist of a fine powder of carbon or of a metal in a matrix of silicone or other vapor-sensitive polymer. The electrical contacts between the powder particles are weakened when the polymer swells or disintegrates, which results in increased resistance. Alternatively, the capacitance between two conductive layers separated by a polymer layer decreases, and hence the impedance increases, when the polymer swells upon exposure to the vapor. In yet another embodiment, the polymer exerts a stress on a piezoresistive element and the stress is increased when the polymer swells, which causes a further increase in resistance. The changes are measured by an impedance-measuring circuit, such as a Wheatstone bridge.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.