Interface circuit for capacitive sensor

Details Interface circuit for capacitive sensor Interface circuit for capacitive sensor

1997-10-31

1999-11-16

Ton, My-Trang Nu

Miscellaneous active electrical nonlinear devices, circuits, and

Specific identifiable device, circuit, or system

Unwanted signal suppression

7351432, 327 94, G08C 1910

Patent

active

059864974

ABSTRACT:
An interface circuit for a capacitive sensor capable of outputting a detection signal with high stability and reliability while suppressing to a minimum the influence of offset and temperature dependency onto the output signal. In a differential capacitance type sensor having a common electrode connected to the ground potential, an electric discharge redistributing method and impedance conversion technique are adopted for obtaining an output voltage which is in proportion to the inter-electrode relative displacement. A switching mechanism is provided for mitigating an offset voltage component contained in the output due to an input offset voltage of the operational amplifier. Further, the sensitivity of the capacitive sensor is increased with the temperature-dependent drift of the sensor output being suppressed by providing additionally a power source change-over switches for allowing the voltages sampled in response to predetermined clocks to be differentially amplified.

REFERENCES:
patent: 5343766 (1994-09-01), Lee
patent: 5451940 (1995-09-01), Schneider et al.
patent: 5528520 (1996-06-01), Kemp
patent: 5604685 (1997-02-01), Seesink et al.
patent: 5633594 (1997-05-01), Okada
patent: 5751154 (1998-05-01), Tsugai
"A ASIC for High-Resolution Capacitive Microaccelerometers", H. Leuthold et al, Sensors & Actuarores A21-23, 1990, pp. 278-281.

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