Proximity switch having oscillator inductively coupled through pulsed Faraday shield to resonant target
First Claim
1. A combination comprising an inductive type proximity switch which comprises a main LC oscillator circuit, and a target which comprises inductance means, there being means provided which are adapted to be operated by a pulsed input, characterised in that one of the proximity switch and the target includes an open ended loop and said means adapted to be operated by a pulsed input comprise bistate switching means which are connected between the ends of the loop, the bistate switching means being adapted to be operated by the pulsed input to sequentially make and break a connection between the ends of the loop whereby the loop functions as a shield to inhibit mutual inductive linking of the inductance means of the target with inductance means of the main LC oscillator when the target is in proximity with the proximity switch and said connection is made.
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Abstract
An inductive type proximity switch (S) includes an open-ended loop (L3) adjacent to the inductor (L1, L2) of the parallel resonant circuit of its main (LC) oscillator. A high speed bistate switch (S1) is connected between the ends of the loop (L3). A pulsed input to the switch (S1) causes sequential making and breaking of a connection between the ends of the loop (L3) whereby the loop (L3) functions as a Faraday shield to inhibit mutual inductive linking of the inductor (L1, L2) with an inductor (L4) of a passive (LC) resonant circuit (L4, C4) of a target (T) when the target (T) is in proximity with the proximity switch (S) and the connection between the ends of the loop (L3) is made by the bistate switch (S1).
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Citations
16 Claims
- 1. A combination comprising an inductive type proximity switch which comprises a main LC oscillator circuit, and a target which comprises inductance means, there being means provided which are adapted to be operated by a pulsed input, characterised in that one of the proximity switch and the target includes an open ended loop and said means adapted to be operated by a pulsed input comprise bistate switching means which are connected between the ends of the loop, the bistate switching means being adapted to be operated by the pulsed input to sequentially make and break a connection between the ends of the loop whereby the loop functions as a shield to inhibit mutual inductive linking of the inductance means of the target with inductance means of the main LC oscillator when the target is in proximity with the proximity switch and said connection is made.
- 3. An inductive type proximity switch comprising a main LC oscillator circuit and means which are adapted to be operated by a pulsed input, characterised in that said means comprise bistate switching means and said proximity switch also comprises an open-ended loop, said bistate switching means being connected between the ends of the loop and being adapted to be operated by the pulsed input to sequentially make and break a connection between the ends of the loop whereby the loop functions as a shield to inhibit mutual inductive linking of a passive parallel resonant circuit of a target with inductance means of the main LC oscillator when the target is in proximity with the proximity switch and said connection is made.
- 13. A target for use in combination with an inductive type proximity switch, which target comprises inductance means, there being means adapted to be operated by a pulsed input, characterised in that said means adapted to be operated by a pulsed input comprise bistate switching means, and said target further comprises an open ended loop, said bistate switching means being connected between the ends of the loop and being adapted to be operated by the pulsed input to sequentially make and break a connection between the ends of the loop whereby the loop functions as a shield to inhibit mutual inductive linking of the inductance means of the target with inductance means of a main LC oscillator of the proximity switch when the target is in proximity with the proximity switch and said connection is made.
Specification