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US 5,633,594 AGranted
Differential type capacitive sensor system
AssigneeNEC Corporation
InventorHiroyuki Okada
Life of this patent
Estimating the term…
Abstract
In a capacitive sensor system, first and second driving signals opposite in phase are applied to a sensor capacitor and a reference capacitor, respectively, which are both connected to a switched capacitor circuit. An output signal of the switched capacitor is sampled by two sample-and-hold circuits which are operated in different phases of the driving signals. A differential amplifier generates a sensor signal in response to the difference in potential between the outputs of the sample-and-hold circuits.
Claims15
A capacitive sensor system comprising:
- first means for generating a first driving signal;
- second means for generating a second driving signal opposite in phase to said first driving signal;
- a sensor capacitor, connected to said first means, for receiving said first driving signal;
- a reference capacitor, connected to said second means, for receiving said second driving signal;
- a switched capacitor circuit, connected to said sensor capacitor and said reference capacitor, for generating a signal corresponding to a difference in capacitance between said sensor capacitor and said reference capacitor;
- a first sample-and-hold circuit, connected to said switched capacitor circuit, for sampling and holding an output of said switched capacitor circuit when said first and second driving signals are high and low, respectively;
- a second sample-and-hold circuit, connected to said switched capacitor circuit, for sampling and holding the output of said switched capacitor circuit when said first and second driving signals are low and high, respectively;
- and
- a differential amplifier, connected to said first and second sample-and-hold circuits, for generating and output signal in response to a difference between outputs of said first and second sample-and-hold circuits.
6 more elements
A capacitive sensor system comprising:
- a sensor capacitor;
- a reference capacitor;
- a switched capacitor circuit, connected to said sensor capacitor and said reference capacitor, for generating a signal corresponding to a difference in capacitance between said sensor capacitor and said reference capacitor;
- a first sample-and-hold circuit, connected to said switched capacitor circuit, for sampling and holding an output of said switched capacitor circuit;
- a second sample-and-hold circuit, connected to said switched capacitor circuit, for sampling and holding the output of said switched capacitor circuit;
- a differential amplifier, connected to said first and second sample-and-hold circuits, for generating and output signal in response to a difference between outputs of said first and second sample-and-hold circuits;
- and
- a driving circuit, connected to said sensor capacitor, said reference capacitor, said switched capacitor circuit and said first and second sample-and-hold circuits, for generating a first driving signal having a definite time period and applying said first driving signal to said sensor capacitor, generating a second driving signal opposite in phase to said first driving signal and applying said second driving signal to said reference capacitor, generating a reset signal for a definite time period in advance of a transition of said first and second driving signals and applying said reset signal to said switched capacitor circuit to thereby deactivate said switched capacitor circuit, generating a first sampling and holding signal for a definite time period after a rising transition of said first driving signal and before generation of said reset signal and applying said first sampling and holding signal to said first sample-and-hold circuit to thereby operate said first sample-and-hold circuit, and generating a second sampling and holding signal for a definite time period after a rising transition of said second driving signal and before generation of said reset signal and applying said second sampling and holding signal to said second sample-and-hold circuit to thereby operate said second sample-and-hold circuit.
5 more elements
Dependencies are inferred from the claim text.