Occupancy detector apparatus for automotive safety systems
First Claim
1. Occupant presence detecting means comprising:
- means forming an occupant sensing capacitor having a first capacitance in the presence of an occupant and a second capacitance in the absence of an occupant;
means forming a reference capacitor having a capacitance independent of the presence or absence of an occupant;
means for supplying charging current to said sensing capacitor and said reference capacitor;
first, second and third terminals;
charge detecting means responsive to a first signal applied to said first terminal and operative to simultaneously develop second signal at said second terminal which is commensurate with the capacitance of said occupant sensing capacitor and a third signal at said third terminal which is commensurate with the capacitance of said reference capacitor; and
comparator means responsive to said second and third signals and operative to develop an output signal having a first state when the capacitances of said sensing capacitor and said reference capacitor have a first predetermined relationship, and a second state when said capacitors have a second predetermined relationship.
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Accused Products
Abstract
Occupancy detector apparatus including a metallic electrode disposed to cooperate with the body of an automobile to form an occupant sensing capacitor, a reference capacitor, and an IC capacitance detecting and logic generating circuit. The IC includes a current source for continuously supplying charging current to the sensing capacitor and the reference capacitor, a first charge detecting circuit for detecting the charge on the sensing capacitor, a second charge detecting circuit for detecting the charge on the reference capacitor, and a comparator circuit for comparing the output signals developed by the first and second charge detecting circuits and for developing a logic output commensurate with the relationship between the capacitances of the sensing capacitor and the reference capacitor.
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Citations
5 Claims
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1. Occupant presence detecting means comprising:
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means forming an occupant sensing capacitor having a first capacitance in the presence of an occupant and a second capacitance in the absence of an occupant; means forming a reference capacitor having a capacitance independent of the presence or absence of an occupant; means for supplying charging current to said sensing capacitor and said reference capacitor; first, second and third terminals; charge detecting means responsive to a first signal applied to said first terminal and operative to simultaneously develop second signal at said second terminal which is commensurate with the capacitance of said occupant sensing capacitor and a third signal at said third terminal which is commensurate with the capacitance of said reference capacitor; and comparator means responsive to said second and third signals and operative to develop an output signal having a first state when the capacitances of said sensing capacitor and said reference capacitor have a first predetermined relationship, and a second state when said capacitors have a second predetermined relationship. - View Dependent Claims (2, 3)
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- 4. Occupant presence detecting means as rated in claim 7 wherein said occupant sensing capacitor includes a metallic electrode positioned so as to be separated from a ground plane by a volume of space in which the presence of an occupant is to be detected.
Specification