Capacitative proximity sensing system
First Claim
1. Capacitative proximity sensing system comprisinga leakage field capacitor having a support and two adjacently located planar surface electrodes (11, 13, 31, 32) located on the surface of the support;
- a signal source (14) having one terminal connected to one of the electrodes (11,
31) whereby said one electrode will be a transmitting electrode;
a receiving and evaluation circuit (15-18;
35, 36-42) having one terminal connected to the other electrode (13,
32) whereby said other electrode will be a receiving electrode, said receiving and evaluation circuit evaluating disturbances of the field being emitted by the transmitting electrode;
the other terminal of said signal source being connected to a common ground or chassis connection;
and an electrically floating metallic shield (20,
33) galvanically insulated from said electrodes and from said ground or chassis connection, said shield being located with respect to the electrodes to draw off a portion of the field generated by the transmitting electrode, when in oscillatory state,whereby, when a grounded mass approaches said floating shield, the leakage field drawn off by said shield will increase and thus provide a signal at the receiving electrode sensing proximity of the mass, said signal being evaluated in the evaluation circuit.
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Accused Products
Abstract
A leakage field capacitor has two adjacently located surface electrodes placed on an essentially plane support surface. A signal source is connected to one of the electrodes, so that this electrode, which may then be termed the transmitting electrode, will provide an electrical field which is sensed by the other, receiving electrode, which is connected to an evaluation circuit which evaluates disturbance of the field generated by the transmitting electrode. A metallic shield which is electrically floating i.e., is galvanically isolated with respect to the electrodes is connected to the signal source as well as to the evaluation circuit in such a manner as to draw off a portion of the field generated by the transmitting electrode when a mass connected to a terminal of the electrodes -- for example ground of chassis -- approaches the shield to cause an increase in leakage field being drawn off by the shield and thereby provide a positive signal indication; the grounded mass may, for example, be the finger of a user operating a switch.
255 Citations
8 Claims
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1. Capacitative proximity sensing system comprising
a leakage field capacitor having a support and two adjacently located planar surface electrodes (11, 13, 31, 32) located on the surface of the support; -
a signal source (14) having one terminal connected to one of the electrodes (11,
31) whereby said one electrode will be a transmitting electrode;a receiving and evaluation circuit (15-18;
35, 36-42) having one terminal connected to the other electrode (13,
32) whereby said other electrode will be a receiving electrode, said receiving and evaluation circuit evaluating disturbances of the field being emitted by the transmitting electrode;the other terminal of said signal source being connected to a common ground or chassis connection; and an electrically floating metallic shield (20,
33) galvanically insulated from said electrodes and from said ground or chassis connection, said shield being located with respect to the electrodes to draw off a portion of the field generated by the transmitting electrode, when in oscillatory state,whereby, when a grounded mass approaches said floating shield, the leakage field drawn off by said shield will increase and thus provide a signal at the receiving electrode sensing proximity of the mass, said signal being evaluated in the evaluation circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification