Piezoresistive accelerometer

The piezoresistive accelerometer is a variant of the strain-gauge accelerometer that uses piezoresistive sensors instead of strain gauges. These sensors behave similarly to strain gauges, but allow for greater strain and sensitivity, although they have some stability issues with temperature changes.

A piezoresistive accelerometer has a stable structure consisting of a silicon chip made by micromachining and semiconductor manufacturing technology. A mass and a beam on which a set of piezoresistive resistors are formed on a silicon chip. A set of electrical bridges is formed by such piezoresistive resistors to generate signals proportional to the applied acceleration.

The main advantages of piezoresistive accelerometers are:

  • measurements are possible over a wide frequency range, from ultra-low to high frequencies of several kHz.
  • compact and lightweight
  • high sensitivity
  • highly resistant to acceleration

Instead of sensing capacitance changes in the seismic mass, a piezoresistive accelerometer uses the change in resistance of piezoresistive materials to convert mechanical strain into a DC output voltage. Most piezoresistive designs are either MEMS type (gas damped) or bonded strain gauge type (fluid damped) and are suitable for shock measurements where the frequency range and g level are significantly high.

Piezoresistive accelerometers are widely used in automotive safety testing, including anti-lock braking systems, safety airbags, and traction control systems, as well as in weapons testing and seismic measurements. Micromachined accelerometers are also available and used in various applications, such as sub-millimeter piezoresistive accelerometers in extremely small dimensions used in biomedical applications.

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