Electronic monitoring system stabilized against accidental triggering
US4336491A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 6, 1981 |
| Grant date | Jun 22, 1982 |
| Priority date | — |
| Expiry date | Feb 6, 2001 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03K17/952
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A contactless motion detector, including an oscillator sensitive to an approaching metallic element, includes an electronic switch such as a thyristor triggerable by an output signal from a demodulator comprising a storage capacitor which is alternately chargeable and dischargeable, preferably with constant current, during each cycle of a high-frequency voltage generated by the oscillator. The oscillator voltage is compared with a reference voltage by means of a differential amplifier causing the flow of a charging current into the capacitor when the oscillator voltage exceeds the reference voltage whereas a discharging current flows out of that capacitor in the opposite case. The reference voltage is so chosen that the capacitor charge rises in the course of a few cycles above a predetermined threshold when the oscillator voltage is high but remains below that threshold when it is low.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.