Capacitance proximity switch
Abstract
Abstract The invention refers to a capacitance proximity switch which is more reliable than known devices. This is achieved by using a circuit which makes it possible to use digital circuits instead of linear amplifiers. The device comprises a square wave oscillator, a pulse stretcher fed by the oscillator using the capacitance between two electrically conducting bodies as at least part of the timing capacitance, means for detecting the change of mark-space ratio due to change of capacitance between the said two bodies and the means to operate a switch when the mark-space ratio differs from a predetermined value. The change of capacitance may be caused by changing the distance between the said two bodies or by approaching one or both of the bodies by a third body which latter may be a conductor or an insulator.
Inventors
- 👤 W Urmenyi
Bibliographic Details
Claims Analysis
Total Claims: 6References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-03-26 | 1976-09-25 | 1977-03-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-03-26 | 1980-09-25 | 1981-03-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-03-26 | 1984-09-25 | 1985-03-27 | $7700.00 | Window Closed / Lapsed |