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US 4,731,591 AGranted
Inductive proximity switch having switched capacitor for controlling hysteresis
AssigneeSiemens Aktiengesellschaft
InventorReinhard Weigand
Life of this patent
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Abstract
An inductive proximity switch which consists of an oscillator with an externally controllable resonant circuit as well as of a switching amplifier controllable by the oscillator. It further has a feed or biasing circuit for the oscillator and the switching amplifier. Connected in parallel with the capacitor of the resonant circuit is a capacitor with an electronic switch, the electronic switch being responsive to the output of the switching amplifier. Thereby a simple switching hysteresis is obtained.
Claims2
An inductive proximity switch comprising:
- a resonator circuit having a resonator frequency and an output which changes in the proximity of an external object, said resonator circuit including a first capacitor;
- an oscillator coupled to said resonator output and having an oscillator output coupled to means for generating an amplifier output;
- a second capacitor;
- and
- switching means responsive to said amplifier output for switching said second capacitor in parallel with said first capacitor for changing said resonator frequency.
2 more elements
Dependencies are inferred from the claim text.