Method and apparatus for detecting a change in capacitance of a capacitive proximity sensor
First Claim
1. A method for detecting a change in capacitance of a capacitive sensing element having a nominal capacitance value, the method comprising:
- coupling the sensing element to a first oscillator, said first oscillator generating a first frequency dependent upon the capacitance value of the sensing element; and
comparing said first frequency to a reference frequency, said reference frequency being a second frequency generated by a second oscillator;
wherein the change in capacitance from the nominal capacitance value is detected if said first frequency differs from said reference frequency by a determined frequency value.
2 Assignments
0 Petitions
Accused Products
Abstract
A method for detecting a change in capacitance of a capacitive sensing element having a nominal capacitance value is disclosed. In an exemplary embodiment, the method includes coupling the sensing element to a first oscillator, the first oscillator generating a first frequency dependent upon the capacitance value of the sensing element. The first frequency is compared to a reference frequency generated by a second oscillator. The change in capacitance from the nominal capacitance value is detected if the first frequency differs from said reference frequency by a determined frequency value.
-
Citations
21 Claims
-
1. A method for detecting a change in capacitance of a capacitive sensing element having a nominal capacitance value, the method comprising:
-
coupling the sensing element to a first oscillator, said first oscillator generating a first frequency dependent upon the capacitance value of the sensing element; and
comparing said first frequency to a reference frequency, said reference frequency being a second frequency generated by a second oscillator;
wherein the change in capacitance from the nominal capacitance value is detected if said first frequency differs from said reference frequency by a determined frequency value. - View Dependent Claims (2, 3, 4, 5, 6)
-
-
7. An apparatus for detecting a change in capacitance of a capacitive sensing element having a nominal capacitance value, comprising:
-
a first oscillator coupled to the sensing element, said first oscillator generating a first frequency dependent upon the capacitance value of the sensing element;
a second oscillator generating a reference frequency; and
a device for comparing said first frequency to said frequency;
wherein the change in capacitance from the nominal capacitance value is detected if said first frequency differs from said reference frequency by a determined frequency value. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15)
-
-
16. A capacitive sensing element, comprising:
-
a capacitive strip having a nominal capacitance value; and
a capacitance detection circuit integrated within said capacitive strip, said capacitance detection circuit further comprising;
a first oscillator coupled to the capacitive strip, said first oscillator generating a first frequency dependent upon the capacitance value of the capacitive strip; and
a second oscillator generating a reference frequency, said reference frequency being offset from said first frequency by a fixed offset value when the capacitance of said capacitive strip equals said nominal capacitance value;
wherein a change in capacitance of the capacitive strip from said nominal capacitance value is detected if said first frequency differs from said reference frequency by more than said fixed offset value. - View Dependent Claims (17, 18, 19, 20, 21)
-
Specification