Capacitive sensing system able of using heating element as antenna electrode
First Claim
1. Capacitive sensing system for being connected to a heating element producing heat upon electrical current being caused to flow across it, said capacitive sensing system comprisinga capacitive detector connectable to said heating element, configured for driving an alternating current into said heating element and for producing an output indicative of capacitance based upon said alternating current;
- a common mode choke having a first winding for connecting a first terminal of said heating element with a first terminal of a heating current supply and a second winding for connecting a second terminal of said heating element with a second terminal of said heating current supply, said common mode choke essentially preventing said alternating current from flowing from said heating element to said heating current supply;
wherein said common mode choke comprises a third winding connected in parallel of at least one of said first and second windings, said capacitive detector being further configured for measuring a portion of said alternating current flowing across said third winding and for taking into account said measured portion of alternating current when producing said output.
1 Assignment
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Accused Products
Abstract
A capacitive sensing system for being connected to a heating element comprises a capacitive detector connectable to the heating element and a common mode choke for essentially preventing alternating current from flowing from the heating element to the heating current supply. The capacitive detector is configured for driving an alternating current into the heating element and for producing an output indicative of capacitance based upon the alternating current. The choke has a first and a second winding for connecting the heating element with the heating current supply. The choke comprises a third winding connected in parallel of the first and/or second winding. The capacitive detector is configured for measuring a portion of the alternating current flowing across the third winding and for taking into account the measured portion of alternating current when producing the output.
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Citations
15 Claims
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1. Capacitive sensing system for being connected to a heating element producing heat upon electrical current being caused to flow across it, said capacitive sensing system comprising
a capacitive detector connectable to said heating element, configured for driving an alternating current into said heating element and for producing an output indicative of capacitance based upon said alternating current; -
a common mode choke having a first winding for connecting a first terminal of said heating element with a first terminal of a heating current supply and a second winding for connecting a second terminal of said heating element with a second terminal of said heating current supply, said common mode choke essentially preventing said alternating current from flowing from said heating element to said heating current supply; wherein said common mode choke comprises a third winding connected in parallel of at least one of said first and second windings, said capacitive detector being further configured for measuring a portion of said alternating current flowing across said third winding and for taking into account said measured portion of alternating current when producing said output. - View Dependent Claims (2, 3, 4, 5, 6)
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7. Combined heating and capacitive sensing system, comprising
a heating element for producing heat when electrical current is caused to flow across it, a heating current supply having a first terminal connected to a first terminal of said heating element and a second terminal connected to a second terminal of said heating element so as to form a heating circuit, a capacitive detector connected to said heating element, configured for driving an alternating current into said heating element and for producing an output indicative of capacitance based upon said alternating current; -
a common mode choke having a first winding connected between said first terminal of said heating element and said first terminal of said heating current supply and a second winding connected between said second terminal of said heating element and said second terminal of said heating current supply, said common mode choke essentially preventing said alternating current from flowing from said heating element to said heating current supply; wherein said common mode choke comprises a third winding connected in parallel of at least one of said first and second windings, said capacitive detector being further configured for measuring a portion of said alternating current flowing across said third winding and for taking into account said measured portion of alternating current when producing said output. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15)
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Specification