CAPACITIVE SENSOR CONFIGURED FOR USING HEATING ELEMENT AS ANTENNA ELECTRODE
First Claim
1. A capacitive sensor, configured for being connected between a heating element and a heating current supply and for using said heating element as antenna electrode, comprisinga common mode choke having first and second inductively coupled windings, said first winding for being connected between a first terminal of said heating current supply and a first terminal of said heating element and said second winding for being connected between a second terminal of said heating element and a second terminal of said heating current supply;
- said common mode choke further comprising a third winding inductively coupled with said first and second windings, anda control and evaluation circuit configured to inject an AC signal into said heating element via a measurement node, to measure a voltage on and/or a current across said measurement node, and to derive an impedance between said heating element and a counter electrode from said measured voltage and/or current, andwherein said measurement node is operatively coupled to said third winding for inductively injecting said AC signal into said heating element.
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Accused Products
Abstract
A capacitive sensor configured for connection between a heating element and a heating current supply comprises a common mode choke (CMC) for AC-decoupling the heating element from the heating current supply. The CMC comprises first and second inductively coupled windings, the first winding for connection between a first terminal of the heating current supply and a first terminal of the heating element and the second winding for connection between a second terminal of the heating element and a second terminal of the heating current supply. The capacitive sensor further comprises a control and evaluation circuit for injecting an AC signal into the heating element via a measurement node, measuring a voltage on and/or a current across the measurement node, and to derive an impedance between the heating element and a counter electrode from the measurement. The CMC comprises a third winding inductively coupled with the first and second windings, the third winding being operatively coupled with the measurement node.
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Citations
12 Claims
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1. A capacitive sensor, configured for being connected between a heating element and a heating current supply and for using said heating element as antenna electrode, comprising
a common mode choke having first and second inductively coupled windings, said first winding for being connected between a first terminal of said heating current supply and a first terminal of said heating element and said second winding for being connected between a second terminal of said heating element and a second terminal of said heating current supply; - said common mode choke further comprising a third winding inductively coupled with said first and second windings, and
a control and evaluation circuit configured to inject an AC signal into said heating element via a measurement node, to measure a voltage on and/or a current across said measurement node, and to derive an impedance between said heating element and a counter electrode from said measured voltage and/or current, and wherein said measurement node is operatively coupled to said third winding for inductively injecting said AC signal into said heating element. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
- said common mode choke further comprising a third winding inductively coupled with said first and second windings, and
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11. Occupancy sensor for a vehicle seat (25), comprising a capacitive sensor configured for being connected between a heating element for said vehicle seat and a heating current supply and for using said heating element as antenna electrode, said capacitive sensor comprising
a common mode choke having first and second inductively coupled windings, said first winding for being connected between a first terminal of said heating current supply and a first terminal of said heating element and said second winding for being connected between a second terminal of said heating element and a second terminal of said heating current supply; - said common mode choke further comprising a third winding inductively coupled with said first and second windings, and
a control and evaluation circuit configured to inject an AC signal into said heating element via a measurement node, to measure a voltage on and/or a current across said measurement node, and to derive an impedance between said heating element and a counter electrode from said measured voltage and/or current, and wherein said measurement node is operatively coupled to said third winding for inductively injecting said AC signal into said heating element.
- said common mode choke further comprising a third winding inductively coupled with said first and second windings, and
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12. Hands-on or hands-off detector for a steering wheel (28), comprising a capacitive sensor configured for being connected between a heating element for said steering wheel and a heating current supply and for using said heating element as antenna electrode, said capacitive sensor comprising
a common mode choke having first and second inductively coupled windings, said first winding for being connected between a first terminal of said heating current supply and a first terminal of said heating element and said second winding for being connected between a second terminal of said heating element and a second terminal of said heating current supply; - said common mode choke further comprising a third winding inductively coupled with said first and second windings, and
a control and evaluation circuit configured to inject an AC signal into said heating element via a measurement node, to measure a voltage on and/or a current across said measurement node, and to derive an impedance between said heating element and a counter electrode from said measured voltage and/or current, and wherein said measurement node is operatively coupled to said third winding for inductively injecting said AC signal into said heating element.
- said common mode choke further comprising a third winding inductively coupled with said first and second windings, and
Specification