Imported: 23 Feb '17 | Published: 22 Oct '02
USPTO - Utility Patents
An exemplary embodiment of the invention is a sensing circuit for use with a proximity sensor having a first electrode and a second electrode and a capacitance between the first electrode and the second electrode. The sensing circuit includes a signal generator for generating an alternating signal. The signal generator is for connection to the first electrode of the sensor. A synchronous detector has a first input for connection to the second electrode of the sensor. A phase shifter is coupled to the signal generator and generates a phase shifted signal in response to the alternating signal. The phase shifted signal is provided to a second input of the synchronous detector. The synchronous detector detects a change in the capacitance between the first electrode and the second electrode in response to a signal from the second electrode and the phase shifted signal.
The present invention will now be described, by way of an example, with reference to the accompanying drawings, in which:
a shows, in part, a signal generator;
b shows, in part, a synchronous detector;
c shows, in part, a low pass filter;
d shows, in part, an inverter as well as an attenuator;
e shows, in part, an extension of an equivalent of the operational amplifier;
1. A sensing circuit for use with a proximity sensor having a first electrode and a second electrode and a capacitance between the first electrode and second electrode, the sensing circuit comprising:
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10. A method of detecting a response of a proximity sensor having a first electrode and a second electrode and a capacitance between the first electrode and second electrode, the method comprising:
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