Electronic proximity sensor
US4663542A · kind A · utility
Inventors
Key dates
| Filing date | Jul 30, 1984 |
| Grant date | May 5, 1987 |
| Priority date | — |
| Expiry date | Jul 30, 2004 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03K17/955
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
An electronic sensor of the contactless type has a free-running oscillator with internal positive feedback supplemented by an external negative feedback including a capacitive path whose impedance is normally high but is lowered in the presence of an object to be detected, thereby reducing the output signal of the oscillator from a normal amplitude above a predetermined level to a diminished amplitude below that level. The negative feedback is provided through an IGFET, e.g. of n-channel depletion type, with the aid of a capacitor bridging its source and gate electrodes to form with the external capacitance a voltage divider for the output signal of the oscillator.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.