An accelerometer is a device that measures proper acceleration. The proper acceleration measured by an accelerometer is not necessarily the coordinate acceleration (rate of change of velocity). Instead, the accelerometer sees the acceleration associated with the phenomenon of weight experienced by any test mass at rest in the frame of reference of the accelerometer device. In commercial devices, piezoelectric, piezoresistive and capacitive components are commonly used to convert the mechanical motion into an electrical signal.Piezoelectric accelerometers rely on piezoceramics (e.g. lead zirconate titanate) or single crystals (e.g. quartz, tourmaline). They are unmatched in terms of their upper frequency range, low packaged weight and high temperature range. Piezoresistive accelerometers are preferred in high shock applications. Capacitive accelerometers typically use a silicon micro-machined sensing element. Their performance is superior in the low frequency range and they can be operated in servo mode to achieve high stability and linearity.

Piezoelectric Accelerometer

Piezo electric accelerometer is based on principle of piezo electric effect. A Piezo electric substance is one that produces an electric charge when a mechanical stress is applied.  In a Piezo electric accelerometer a mass is attached to a Piezo electric crystal which is in turn mounted to the case of the accelerometer. When the body of the accelerometer is subjected to vibration the mass mounted on the crystal wants to stay still in space due to inertia and so compresses and stretches the piezo electric crystal. This force causes a charge to be generated and due to Newton law (F=ma) this force is in turn proportional to acceleration. The charge output is converted to voltage output by the use of integral electronics (for example: in an IEPE accelerometer) or made available as a charge output (pc /g) in a charge output Piezo electric accelerometer.

Applications of Accelerometers

  • Used in cars to study shock and vibrations.
  • Camcorders use accelerometers for image stabilization.
  • Still cameras use accelerometers for anti-blur capturing.
  • Used in mobile phones for multiple functions including tilt detection, motion detection.
  • Process control systems and safety installations in industries.
  • Used to measure seismic activity, inclination, machine vibration, dynamic distance and speed with or without the influence of gravity.