Sensing element and detection system employing such element for detection of environmental borne material
US3989463A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 26, 1975 |
| Grant date | Nov 2, 1976 |
| Priority date | — |
| Expiry date | Aug 26, 1995 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N27/227
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An air pollutant and/or fire combustion sensing apparatus includes a pair of sensing electrodes separated by a free space to define a capacitance unit. At least one of the electrodes includes a corrosion-resistant, conductive material which interacts with air borne products to alter the permittivity and/or charge transfer characteristic of the unit. The material is in the form of a highly corrosion-resistant metal selected from a metal or metal alloy including at least one of the metals selected from the Group VIII, periods 4, 5, and 6 of the periodic table, particularly rhodium and stainless steel. Carbon and copper respond to produce a detectible output. An amplifying and alarm circuit is connected to the capacitance unit, and responds to either an increase or a decrease in the capacitance as a result of the interaction with the sensing electrode material. The circuit includes a thermally stabilized field effect transistor as a buffer input amplifier connected in differential configuration to produce a high input impedance and a high gain. The transistor is connected to a high gain DC operational amplifier having a feedback compensation network to compensate for thermal and low f…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.