Capacitive Pressure Sensor Characteristics

Advantages of capacitive sensors compared with piezoresistive devices:

• Scaling down the device dimensions is easier
  because concerns about sress averaging and resistor tolerance are eliminated
• No mechanical contact, friction error or hysteresis errors in the measurement
• High stability and reproducibility
• Minimum dependence on the temperature
  because the dielectric constant changes little with temperature
• High temperature operation (>125 oC)
• MEMS technology enables to manufacture signal conditioning circuits on the same wafer,
  very close to the sensor. Thus the 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 of capacitive sensors:

• Capacitance changes nonlinearly with diaphragm displacement and applied pressure
• Output impedance of the device is large
  this 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.
  It must be placed in close proximity to the device in a hybrid or monolithic implementation.
• Transferring a signal at the counter electrode out of the cavity in the case of absolute pressure sensors
  can present a substantial manufacturing challenge

More details

Related reading

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

Ko W.H., "Solid-state capacitive pressure transducers", Sensors and Actuators, vol. 10, p. 303-320, 1986.

Ko, W.H., Wang, Q., Wang, Y., Touch Mode Pressure Sensors for Industrial Applications, in Solid-State Sensor and Actuator Workshop, pp. 244?248, 1996.

Middelhoek S., Audet S. A., Silicon sensors, Academic Press, 1989.

Omi, T., Horibata, K., Sato, F., Takeuchi, M., Capacitive pressure sensor with center clamped diaphragm, IEICE Trans. Electron. Vol. E80-C, No. 2, pp. 263-268, 1997.

Park, Y. E., Wise K. D., "An MOS switched capacitor readout amplifier for capacitive pressure sensors", in Record of the IEEE Custom IC Conference, and Microsensors, R. S. Muller et al., Eds., IEEE Press, New York, pp. 329-333, 1990.

Peters, D., Bechtold, S., Laur, R., Optimized behavioral model of a pressure sensor including the touch-down effect, in Technical Proceeding of the 1999 Int. Conf. on Modeling and Simulation of Microsystems, pp. 237-240, 1999.

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

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

Zhang Y., Wise K. D., "An ultra-sensitive capacitive pressure sensor with a bossed dielectric diaphragm", Tech. Dig. IEEE Solid-State Sensors and Actuator Workshop, 205-208, 1994.