Accelerometer
An accelerometer is a device for measuring acceleration. An accelerometer inherently measures its own motion (locomotion), in contrast to a device based on remote sensing.
One application for accelerometers is to measure gravity, wherein an accelerometer is specifically configured for use in gravimetry. Such a device is called a gravimeter.
Accelerometers are used along with gyroscopes in inertial guidance systems, as well as in many other scientific and engineering systems. One of the most common uses for micro electro-mechanical system (MEMS) accelerometers is in airbag deployment systems for modern automobiles. In this case the accelerometers are used to detect the rapid deceleration of the vehicle to determine when a collision has occurred and the severity of the collision.
Accelerometers are perhaps the simplest MEMS device possible, sometimes consisting of little more than a suspended cantilever beam or proof mass (a.k.a. seismic mass) with some type of deflection sensing and circuitry. MEMS Accelerometers are available in a wide variety of ranges up to thousands of gn's. Single axis, dual axis, and three axis models are available.
The widespread use of accelerometers in the automotive industry has pushed their cost down dramatically.
There is currently research investigating using accelerometers to help estimate the location of devices. The Global Positioning System can only provide information to a device where it can receive signals. When a device is in a tunnel, it can make use of an accelerometer to infer position.
Types of accelerometer:
- Piezo-film or piezoelectric sensor
- Surface Micromachined Capacitive (MEMS) — Analog Devices, Motorola, Honeywell, Systron Donner (BEI)
- Thermal (submicron CMOS process) — MEMSIC
- Bulk Micromachined Capacitive — VTI Technologies
- Bulk Micromachined Piezo Resistive
- Electromechanical Servo (Servo Force Balance ???)
- Null-balance
- Strain gauge
- Resonance
- Magnetic induction
- Optical
- Surface Acoustic Wave (SAW)
In biology
Many aquatic invertebrates use statocysts, special cellular structures with pendulous weights and enervated sensory organs to measure acceleration and gravity.
In humans, the vestibular apparatus in the inner ear provides information about acceleration to the brain, used for coordination and balance. In people whose sense of balance is injured or defective, this function can be regained through the use of a wearable MEMS-based sensor.
Other uses
It has been revealed that the "nunchaku" peripheral featured with the Nintendo Wii free-hand pointer input device will contain an accelerometer. The cited source below suggests the device may be used in first-person, or light-gun type shooting games where the accelerometer peripheral can be tilted left or right to reload the player's weapon. However, this ought to just be the tip of the iceberg, as the full suite of sensors in the controller allow the Wii to calculate where the device is in 3D space, as well as it's orientation.