Sampled-data interface circuit for capacitive sensors

Details Sampled-data interface circuit for capacitive sensors Sampled-data interface circuit for capacitive sensors

1995-09-25

1997-08-26

Williams, Hezron E.

Measuring and testing

Speed, velocity, or acceleration

Acceleration determination utilizing inertial element

73862581, 73 188, 324658, G01P 15125, G01L 102, G01R 2726

Patent

active

056612400

ABSTRACT:
In one embodiment of the present invention, a sensing system utilizing a capacitive sensor includes an integrator which is connected to the sensor and has an operational amplifier and an integrator capacitor, a reference voltage source, a clock generator generating a 3-phase clock, and a number of switches. The switches, during the first phase of the clock connect the sensor capacitors to the reference voltages and cause the capacitors to become charged, and connect the output and the input of the amplifier cand cause the integrator to be shorted. During the second phase, the switches connect the sensor capacitors contained in the capacitive sensor to the ground and disconnect the input of the integrator from the output of the integrator to cause the charges on the sensor capacitor to be transferred to the integrator capacitor. During the third phase, the switches connect the sensor capacitors to the output of the integrator, and the integrator capacitor to the groung so that the charge is transferred from the integrator capacitor to the sensor capacitors of the capacitive sensor. Thus, the output of integrator becomes a scaled version of the difference over the sum of the sensor capacitors. The scale factor can be adjusted by adjusting the reference voltage.

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"Surface Micromachined Accelerometers" Bernhard E. Boser and Roger T. Howe, University of California, Berkeley, CA 94720-1770.

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