Patent ID: 7417441

Claim:
A method for determining a measurable capacitance for proximity detection in a sensor having a plurality of sensing electrodes and a guarding electrode proximate the plurality of sensing electrodes, the method comprising: executing a charge transfer process for a number of executions equal to at least two, wherein the charge transfer process comprises the steps of: applying a pre-determined voltage to at least one of the plurality of sensing electrodes using a first switch; applying a first guard voltage to the guarding electrode using a second switch; sharing charge between the at least one of the plurality of sensing electrodes and a passive network that includes a filter capacitance such that shared charge accumulates on the filter capacitance; and applying a second guard voltage different from the first guard voltage to the guarding electrode; and measuring a voltage on the filter capacitance for a number of measurements equal to at least one to produce at least one result to determine the measurable capacitance for proximity detection.