Contactless oscillator-type proximity sensor with constant-voltage impedance
US3935542A · kind A · utility
Inventor
Key dates
| Filing date | Jan 22, 1973 |
| Grant date | Jan 27, 1976 |
| Priority date | — |
| Expiry date | Jan 22, 1993 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03K17/9547
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A contactless proximity sensor includes an oscillator which generates an output damped by the presence of a metal part whose approach is to be detected. The operating voltage for the oscillator is developed across a capacitor, in parallel with a Zener diode, whose charging circuit includes a high-ohmic resistance connected in series therewith across a supply of pulsating direct current. The flow of charging current into the capacitor is controlled by a thyristor adapted to be fired by means of a trigger transistor upon a critical reduction in the amplitude of the oscillator output. The trigger transistor, upon conducting, lowers the cathode potential of the thyristor whose gate is connected, via a resistor and/or a diode, to the junction of the capacitor with its charging resistance; in one embodiment this gate is driven positive through an inverter upon the conduction of the trigger transistor. The thyristor may shunt only the charging resistance, or it may be connected in series with a second Zener diode across the voltage-generating network consisting of the first Zener diode, the capacitor and its charging resistance.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.