Accelerometer
An accelerometer is an electromechanical device that will measure acceleration forces. These forces may be static, like the constant force of gravity pulling at your feet, or they could be dynamic - caused by moving or vibrating the accelerometer.
Uses
Some accelerometers use the piezoelectric effect - they contain microscopic crystal structures that get stressed by accelerative forces, which causes a voltage to be generated. Another way to do it is by sensing changes in capacitance. If you have two microstructures next to each other, they have a certain capacitance between them. If an accelerative force moves one of the structures, then the capacitance will change. Add some circuitry to convert from capacitance to voltage, and you will get an accelerometer. There are even more methods, including use of the piezoresistive effect, hot air bubbles, and light.
Examples
- Apple uses an LIS302DL accelerometer in the iPhone, iPod Touch and the 4th generation iPod Nano allowing the device to know when it is tilted on its side.
- Apple’s Sudden Motion Sensor, which is used to detect drops. If a drop is detected, the heads of the hard disk are parked to avoid data loss by the ensuing shock.
- The Wii Remote for the Wii game console contains a three-axis accelerometer from Analog Devices to sense movement which complements its pointer functionality. This provides more realistic game control.
Types
- Capacitive - sense a change in capacitance related to acceleration
- Piezoelectric - piezocrystal emits a charge when subjected to a “g” force, mounted to mass–voltage output converted to acceleration
- Piezoresistive - uses a piezo-resistive substrate feature whose resistance changes with acceleration
- Hall Effect -Motion converted to electrical signal by sensing of changing magnetic fields