Seat heater and capacitive occupancy sensor combination
First Claim
Patent Images
1. A combined heater and capacitive occupancy sensor, comprising:
- a heater network including a heating element connected between a first node and a second node and configured to dissipate heat when a heating current is caused to flow between said first and second nodes, said first and second nodes being connected via a common mode choke to a heater power supply;
a capacitive sensing network connected to said heating element, said capacitive sensing network configured to apply an oscillating signal to said heating element and to derive a capacitive load of said heating element from a current flowing into or a voltage resulting on said heating element in response to an application of said oscillating signal;
said capacitive sensing network comprising an AC signal source and a current meter connected in series to one of said first and second nodes and a control and detection circuit configured for measuring a voltage applied to and a current flowing into said heating element in response to said voltage,wherein said AC signal source is configured for generating AC signals with at least a first carrier frequency and at least a second carrier frequency, said second carrier frequency being different from said first carrier frequency, and wherein said control and detection circuit is configured for measuring said voltage and said current at least for said two different carrier frequencies generated by said AC signal source.
1 Assignment
0 Petitions
Accused Products
Abstract
In a combined seat heater and capacitive occupancy sensor, the present invention proposes to perform two measurements with two different frequencies. In a first step, the carrier frequency is set to a first known carrier frequency, the complex current through inductance and unknown capacitance and complex drive voltage are measured. In a second step, the carrier frequency is set to a second known carrier frequency, the complex current through inductance and unknown capacitance and complex drive voltage are measured. The measured complex values are used in a formula which yields the unknown capacitance.
-
Citations
10 Claims
-
1. A combined heater and capacitive occupancy sensor, comprising:
-
a heater network including a heating element connected between a first node and a second node and configured to dissipate heat when a heating current is caused to flow between said first and second nodes, said first and second nodes being connected via a common mode choke to a heater power supply; a capacitive sensing network connected to said heating element, said capacitive sensing network configured to apply an oscillating signal to said heating element and to derive a capacitive load of said heating element from a current flowing into or a voltage resulting on said heating element in response to an application of said oscillating signal;
said capacitive sensing network comprising an AC signal source and a current meter connected in series to one of said first and second nodes and a control and detection circuit configured for measuring a voltage applied to and a current flowing into said heating element in response to said voltage,wherein said AC signal source is configured for generating AC signals with at least a first carrier frequency and at least a second carrier frequency, said second carrier frequency being different from said first carrier frequency, and wherein said control and detection circuit is configured for measuring said voltage and said current at least for said two different carrier frequencies generated by said AC signal source. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
-
Specification