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Capacitive Accelerometer Characteristics

Advantages

An important advantage of capacitive accelerometers is that there is no inherent temperature sensitivity
Dielectric constants changes little with temperature
The only thermal effect is a change in the capacitance due to thermal expansion of the constituent elements
A symmetrical sensor design reduces the effect of thermal expansion to a minimum, so that these sensors often do not need any active temperature compensation
High temperature operation (>125 oC)
Scaling down the device dimensions is easier than in the case of piezoresistive sensing
Concerns about stress averaging and resistor tolerance are eliminated
No mechanical contact, friction error or hysteresis errors in the measurement.
High stability
High reproducibility
MEMS technology enables to manufacture signal conditioning circuits, needed to make the measurement, on the same wafer, very close to the sensor
Interference of stray capacitance can be reduced to a minimum and the sensor still has a very small size
Virtually no power consumption
High overpressure capability and high resistance to pressure shocks

Limitations

The capacitance changes nonlinearly with diaphragm displacement and applied pressure
Output impedance of the device is large
Affects the interface circuit design
Parasitic capacitance between the interface circuit and the device output can have a significant negative impact on the readout
Circuit must be placed in close proximity to the device in a hybrid or monolithic implementation
Transferring the signal at the counter electrode can be difficult in the case of absolute pressure sensors
In order to retain the hermetic seal

More information

Related Reading

Asch G., Les capteurs en instrumentation industrielle, Dunod, 1982.

Gad-el-Hak M. (ed.), The MEMS Handbook, CRC Press, 2002.

Lemkin M., Boser B.E., "A three-axis micromachined accelerometer with a CMOS position-sense interface and digital offset-trim electronics", IEEE J. Solid-State Circuits, vol. 34, pp. 456-468, 1999.

Petersen K.E., Shartel A., Raley N.F., ?Micromechanical accelerometer integrated with MOS detection circuitry?, IEEE Trans. Electron Devices, vol. ED-29, pp. 23-27, 1982.

Ristic, L., Sensor Technology and Devices, Artech House, 1994.

Rudolf, F., "A micromechanical capacitive accelerometer with a two-point inertial-mass suspension", Sensors and Actuators, vol. 4, pp. 191-8, 1982.

Rudolf, F., Jornod A., Bencze, P., ?Silicon microaccelerometer?, Transducers 87, Tokyo, Japan, Dig. Of Tech Papers, pp. 395-8, 1987.

Rufer L., Les microsystemes electromecaniques. in Mir, S. (Ed.), Les applications des microsystemes sur silicium. Traite EGEM, Hermes Science Publications, pp. 19-64, 2002.

Seidel H., Riedel H., Kolbeck R., M?, Kupke W., K?er M., "Capacitive silicon accelerometer with highly symmetrical design", Sensors and Actuators, vol. A21-A23, pp. 312-315, 1990.

Senturia S. D., Microsystem Design, Kluwer Academic Publishers, 2001.

Zimmermann L., Ebersoh J.Ph., Le Hung F., Berry J.P., Baillieu F., Rey P., Diem B., Renard S., Caillat P., "Airbag application: a microsystem including a silicon capacitive accelerometer, CMOS switched capacitor electronics and true self-test capability", Sensors and Actuators, vol. A 46-47, pp. 190-195, 1995.