Patent ID: 7282927
Filing Date: 2007-10-16
Classification: G01R,G05B

Abstract:
1. An apparatus for measurement of capacitance by an input-cell, said input-cell comprising: a comparator having a first input and a second input, said capacitance connected between said first input and a ground; a first resistor and a second resistor connected in series between a first voltage reference source and said first input; a first switch connected to the first resistor, the second resistor and the ground, said first switch adapted to receive a first control signal from a first control line and to switch between an open state and a closed state in response to the first control signal with the first resistor, the second resistor and the first switch being adapted to provide charging and discharging to said capacitance when the first switch is open and when the first switch is closed respectively; a third resistor and fourth resistor connected in series between a second voltage reference source, a second switch and a waveform input line, said third resistor and fourth resistor connected to said second input; said second switch being adapted to receive a second control signal from a second control line and to transition between an open state and a closed state based upon a second control signal to switch the second input between said waveform input signal and a biased and attenuated waveform input signal when the second switch is open and when the second switch is closed respectively; and a system clock used to synchronize at least said waveform input, the first control signal and the second control signal; wherein said comparator is adapted to generate a signal at an output that indicates whether an amplitude of a signal at the first input is greater than an amplitude of a signal at the second input; and wherein said first control signal initiates at least one charge and discharge cycle of said capacitance; and wherein said generated output signal is measured by a cumulative count of said system clock and is indicative of a value of the capacitance.