Patent ID: 7777503
Filing Date: 2010-08-17
Classification: G01D,G01R,H03K

Abstract:
1. A system for determining a capacitance value associated with a sensor electrode, the system comprising: a guarding electrode proximate to the sensor electrode; an integrating capacitance configured to store charge received from the sensor electrode; a charge changing circuit coupled to the integrating capacitance; and a controller configured to apply a guard signal to the guarding electrode, the guard signal comprising a waveform having at least two different voltages, the controller further configured to determine the capacitance value by repeatedly applying a voltage to the sensor electrode, repeatedly sharing charge between the sensor electrode and the integrating capacitance to accumulate charge on the integrating capacitance, repeatedly measuring a voltage on the integrating capacitance using a quantizer of the controller, generating quantized values responsive to the repeated measurings, repeatedly changing charge on the integrating capacitance based on the quantized values using the charge changing circuit, and determining the capacitance value of the measurable capacitance from the quantized values.