Accelerometre

An accelerometre, or accelerometer, is a sensor that measures acceleration. In physics, acceleration is the rate of change of velocity; a proper accelerometer measures proper acceleration, which is the acceleration relative to free fall. In practical terms, accelerometers sense linear motion along one or more axes and can be used to determine orientation with respect to gravity when stationary.

Most modern accelerometers are microelectromechanical systems (MEMS). They typically use a moving proof mass attached to a suspension and a capacitive, piezoelectric, or other transduction method to convert inertial forces into an electrical signal. The most common type in consumer electronics is a MEMS capacitive accelerometer, often available as a 3-axis device that outputs three simultaneous measurements.

Electrical outputs may be analog voltage, or digital data via interfaces such as I2C or SPI. Measurements are expressed in meters per second squared (m/s^2) or in gravitational units (g). Dynamic range, bandwidth, sensitivity, and noise characterize performance; typical consumer devices use ranges around ±2 g to ±16 g.

Applications include sensing device orientation and motion in smartphones and wearables, in automotive systems for airbag deployment, rollover detection, and stability control, and in navigation and inertial measurement units when GPS signals are unreliable. In engineering, accelerometers are used in vibration monitoring and structural health.

Calibration and limitations: accelerometers can exhibit bias that drifts with temperature, scale-factor errors, and noise. They require calibration and, in many cases, fusion with gyroscopes and magnetometers to provide robust attitude and motion estimates.