An accelerometer is an electro-mechanical device that measures acceleration in one or more directions. Usually X, Y, and Z are measured, but angular acceleration can also be measured with certain types. Large values indicate large accelerations or sudden stops (module hits floor). Acceleration is not the same as a position measurement! Some variants include a gyroscopic sensor, so a static null position can be measured, as well as the dynamic accelerations in one or more directions.

Acceleration is the increase or decrease in speed in a given time interval, so the change in velocity. As you may remember from physics lessons, you can integrate acceleration over time to get velocity and you can integrate that once more to get the position. The big drawback of doing that is that the calculated position is not very accurate as all errors are integrated as well. That means you have to calibrate your position every once and awhile to be accurate (enough).

Most important specifications

• Sensing range: the upper and lower limits of what the accelerometer can measure, usually expressed in g (1 g is about 9.8 m/s²).
• Number of axes measured (can be 1, 2, or 3)
• Power usage (especially important in mobile applications)
• Communication interface (analog signal, or digital via SPI, or I²C).

Applications

Vibration meter, model plane, detect earthquakes, motion feedback in swimmers to perfect a stroke, hard drive protection when a laptop is falling.