Non-conductive polar gas sensing element and detection system
US4247299A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 19, 1978 |
| Grant date | Jan 27, 1981 |
| Priority date | — |
| Expiry date | Jun 19, 1998 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N27/60
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An air pollutant and/or fire combustion sensing apparatus includes a sensing electrode having an electrically non-conductive or dielectric sensing layer which has a surface resistivity in excess of 1.times.10.sup.10 ohms/square (and preferably 1.times.10.sup.15), and a bulk resistivity in excess of 1.times.10.sup.12 ohm-cm, and preferably 1.times.10.sup.15 at 50% R.H., and which is essentially free of dipole-hydrogen bonding forces such that the surface energy component is primarily due to dispersion bonding forces and, if at all, only incidentally as a result of dipole-hydrogen bonding forces. The latter appears to be a principal factor and desirably has a value of less than 5.0 ergs/cm.sup.2 and preferably less than 1.0 erg/cm.sup.2. The gases detected have a large Van der Waal gas "a" constant and dipole moment. This sensing layer adsorbs air borne polar constituents to alter the charge on the electrode. Optimum results are obtained with polytetrafluoroethylene (Teflon TFE), perfluoroalkoxy (Teflon PFA), fluorinated ethylene-propylene (Teflon FEP), polystyrene or polyethylene. A high input impedance detecting circuit with good electrometer characteristics responds to the change …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.