DescriptionAn accelerometer is an instrument used for measuring acceleration and gravity induced reactions. Accelerometers are capable of sensing the tilt of an object, or inclination. They can also sense vibration, and shock. With producers of electronics constantly looking for new and innovative ideas, they have looked to accelerometers to enhance their products. Small electronics, like cameras and even the new iPods feature accelerometers to enhance the user’s overall experience. However, accelerometers also serve a useful purpose for many other industries, including the medical field, transportation, science and engineering.

Accelerometers were evented by George Atwood in 1783, and was originally called Atwood Machines. The early generation of accelerometers measured linear acceleration by the method of Newton's second law: Force=Mass(Acceleration).


Atwood Machine
Atwood Machine

Later on accelerometers were developed to measure circular movement. this was measured with a string with a weight attached to the end of it. The accelerometer has since developed and is now used with seismographs, laptop computers, and cars. Accelerometers are used in dummies to recieve impact data from crash tests.

Applications
Medical Applications
An automated external defibrillator makes use of accelerometers in measuring the depth of CPR chest compressions. An automated external defibrillator, or AED, is used when a patient is experiencing a life threatening abnormality with their heart rhythms; whether the heart is beating too fast or too slow. With the assistance of accelerometers, the AED diagnoses the patient’s status and determines the appropriate amount of shock to deliver, in order to restore the patient’s heart to a safe rhythm.

Accelerometers are also used in the aid of personal fitness. Nike has produced a footpod with an accelerometer, which when paired with a specially designed wristwatch can calculate the speed and distance of the runner wearing the unit. Body mounted accelerometers can be used in context aware computing systems and for measuring aspects of human performance, which may be used for teaching and demonstrating skill acquisition, coaching sporting activities, sports and human movement research, and teaching subjects such as physics and physical education. Analysis is restricted to considerations as to how raw data can be used, and how simple calculations of quantities of data in the time domain, can be used. The limitations of the use of such data are discussed.

Transportation
In the event of an airbag deploying, you can thank an accelerometer. In most new vehicles accelerometers are used to detect a rapid deceleration of the vehicle to determine if a collision has occurred, and how severe the collision is. If the accelerometer finds that the collision is severe enough, the airbag will deploy. Accelerometers are also used in automotive electronic stability control systems, which keep the car under control when taking corners at high speeds.

Accelerometers are also located in civilian and military airplanes. These accelerometers provide important information to the pilots and onboard computers that help to provide safety features and a comfortable flight. The accelerometer sensors in the aircrafts monitor G force for stress on the plane, turbulence, and a stall velocity display for correcting G loads. Each of these makes small corrections to the onboard computers to help for a safer, more stable flight. Also, in the event of a crash, or an impending crash, the accelerometer activates the ELT (Emergency Locator Transmitter) in the plane, so the pilots can focus on recovery, or in military planes, ejecting.

Consumer Electronics

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Laptops

Although accelerometers have been available commercially for more than 25 years, broad consensus about how to use these tools have not yet been established. Probably the most well known use of accelerometers is their use in consumer electronics. Today, accelerometers are now being put into laptops. They are install into every Apple laptop manufactured since 2004, as well as into post-2003 IBM Thinkpads, and some recent HP and Acer models. The main purpose of the accelerometer in this particular application is to prevent the loss of precious data. If you drop your latop, the accelerometer detects the sudden movement and puts the brakes on your spinning hard drive. The laptop accelerometers are installed into ordinary laptops, which can be combined to detect early signs of seismic waves. An application called SeisMac can already turn a MacBook into a seismograph by displaying accelerometer data in real time.

WiiMote (Three-Axis Accelerometer)
WiiMote (Three-Axis Accelerometer)



Video Games

The Wii Remote for the Nintendo Wii features a three-axis accelerometer which senses the player’s movements and imitates those movements on the television screen. This provides games with a more realistic experience, and sets Nintendo apart from their competitors.

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iPod touch detects when you rotate it from portrait to landscape, then automatically changes the contents of the display. So you immediately see the entire width of a web page, view a photo in its proper aspect ratio, or control a game using only your movements.
Phones & Other Small Gadgets

Many top phone producers have also incorporated the use of accelerometers to enhance the user’s experience and usability. Nokia and Sony both featured accelerometers in some of their earlier versions, but Apple has recently taken a dive into the phone market. With the release of the iPhone Apple has made the technology known as accelerometer known to the public. With the use of accelerometers the iPhone can detect the orientation of the device to display images on the screen in either portrait or landscape, respectfully. Apple also took it one step further with the addition of games, which make use of the accelerometer technology. For example, in a car racing game an individual can rotate the device clockwise, or counter clockwise, and the vehicle in the game imitates the direction you turn the device. The amount of rotation of the device directly relates to the amount of rotation the vehicle will make. The uses of accelerometers in the iPhone have become a widely appreciated technology and have since been added many other devices. They can be found in the new iPod Touch and the 4th generation iPod nano, as well as cameras and other small media devices.


Check out an accelerometer in action with this iPod Touch.....


Related Links

http://en.wikipedia.org/wiki/Accelerometer

http://www.dimensionengineering.com/accelerometers.htm

http://www.apple.com/ipodtouch/features/accelerometer.html

http://www.aircraftspruce.com/menus/in/accelerometers.html