Diagnostic capacitive occupancy or proximity detector
First Claim
1. A capacitive occupancy or proximity detector, comprisinga heating circuit, including a heating element connected between a first and a second node, said first and second nodes configured to connect said heating circuit to a heating current source;
- an impedance measurement circuit connected to said heating element configured to measure impedance between said heating element and a node at ground potential; and
a diagnostic circuit configured to measure electrical resistance across said heating circuit between said first and second nodes, said diagnostic circuit includinga heating current sensor arranged in said heating circuit, configured to sense a heating current across said heating circuit;
a current supply device connected to one of said first and second nodes configured to drive a diagnostic current across said heating circuit; and
a current limiting ground path connected to the other of said first and second nodes, configured to drain said diagnostic current and to block said heating current.
1 Assignment
0 Petitions
Accused Products
Abstract
A capacitive occupancy or proximity detector (10) comprises a heating circuit, an impedance measurement circuit (34, 36, 40) and a diagnostic circuit. The heating circuit includes a heating element (12). The impedance measurement circuit is connected to the heating element so as to measure impedance between the heating element and a node at ground potential. The diagnostic circuit is configured for measuring electrical resistance across the heating circuit and includes a heating current sensor (42), configured for sensing a heating current across the heating circuit, a current supply device (48) for driving a diagnostic current across the heating circuit and a current limiting ground path (50), configured for draining the diagnostic current and for blocking the heating current.
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Citations
24 Claims
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1. A capacitive occupancy or proximity detector, comprising
a heating circuit, including a heating element connected between a first and a second node, said first and second nodes configured to connect said heating circuit to a heating current source; -
an impedance measurement circuit connected to said heating element configured to measure impedance between said heating element and a node at ground potential; and a diagnostic circuit configured to measure electrical resistance across said heating circuit between said first and second nodes, said diagnostic circuit including a heating current sensor arranged in said heating circuit, configured to sense a heating current across said heating circuit; a current supply device connected to one of said first and second nodes configured to drive a diagnostic current across said heating circuit; and a current limiting ground path connected to the other of said first and second nodes, configured to drain said diagnostic current and to block said heating current. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A combined seat heater and seat occupancy sensor comprising a capacitive occupancy or proximity detector, said capacitive occupancy or proximity detector, comprising
a heating circuit, including a heating element connected between a first and a second node, said first and second nodes configured to connect said heating circuit to a heating current source; -
an impedance measurement circuit connected to said heating element configured to measure impedance between said heating element and a node at ground potential; and a diagnostic circuit configured to measure electrical resistance across said heating circuit between said first and second nodes, said diagnostic circuit including a heating current sensor arranged in said heating circuit, configured to sense a heating current across said heating circuit; a current supply device connected to one of said first and second nodes configured to drive a diagnostic current across said heating circuit; and a current limiting ground path connected to the other of said first and second nodes, configured to drain said diagnostic current and to block said heating current. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A combined steering wheel heater and hands-on-detector comprising a capacitive occupancy or proximity detector, said capacitive occupancy or proximity detector, comprising
a heating circuit, including a heating element connected between a first and a second node, said first and second nodes configured to connect said heating circuit to a heating current source; -
an impedance measurement circuit connected to said heating element configured to measure impedance between said heating element and a node at ground potential; and a diagnostic circuit configured to measure electrical resistance across said heating circuit between said first and second nodes, said diagnostic circuit including a heating current sensor arranged in said heating circuit, configured to sense a heating current across said heating circuit; a current supply device connected to one of said first and second nodes configured to drive a diagnostic current across said heating circuit; and a current limiting ground path connected to the other of said first and second nodes, configured to drain said diagnostic current and to block said heating current. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
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Specification