# Accelerometer

accelerometersG-sensoracceleration sensorauto screen rotationaccelerometricaccelerometrydetects movementMotion sensorOrientation sensor3-axis accelerometer
An accelerometer is a device that measures proper acceleration.wikipedia
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### Proper acceleration

physical acceleration
An accelerometer is a device that measures proper acceleration.
In relativity theory, proper acceleration is the physical acceleration (i.e., measurable acceleration as by an accelerometer) experienced by an object.

Highly sensitive accelerometers are components of inertial navigation systems for aircraft and missiles.
An inertial navigation system (INS) is a navigation device that uses a computer, motion sensors (accelerometers) and rotation sensors (gyroscopes) to continuously calculate by dead reckoning the position, the orientation, and the velocity (direction and speed of movement) of a moving object without the need for external references.

### G-force

gg-forcesGs
Such accelerations are popularly denoted g-force; i.e., in comparison to standard gravity.
Despite the name, it is incorrect to consider g-force a fundamental force, as "g-force" is a type of acceleration that can be measured with an accelerometer.

### Inertial frame of reference

inertial frameinertialinertial reference frame
Put another way, at any point in spacetime the equivalence principle guarantees the existence of a local inertial frame, and an accelerometer measures the acceleration relative to that frame.
All inertial frames are in a state of constant, rectilinear motion with respect to one another; an accelerometer moving with any of them would detect zero acceleration.

### Equivalence principle

strong equivalence principleequivalentPrinciple of Equivalence
Put another way, at any point in spacetime the equivalence principle guarantees the existence of a local inertial frame, and an accelerometer measures the acceleration relative to that frame.
This is why an accelerometer in free-fall doesn't register any acceleration; there isn't any.

### Acceleration

decelerationacceleratem/s 2
Proper acceleration, being the acceleration (or rate of change of velocity) of a body in its own instantaneous rest frame, is not the same as coordinate acceleration, being the acceleration in a fixed coordinate system.
Proper acceleration, the acceleration of a body relative to a free-fall condition, is measured by an instrument called an accelerometer.

### Capacitive sensing

capacitiveCapacitive touchcapacitive sensor
In commercial devices, piezoelectric, piezoresistive and capacitive components are commonly used to convert the mechanical motion into an electrical signal.
Many types of sensors use capacitive sensing, including sensors to detect and measure proximity, position and displacement, force, humidity, fluid level, and acceleration.

### Gravimeter

gravimetersgravimetricgravitometer
Applications for accelerometers that measure gravity, wherein an accelerometer is specifically configured for use in gravimetry, are called gravimeters.
The first gravimeters were vertical accelerometers, specialized for measuring the constant downward acceleration of gravity on the earth's surface.

### Quake-Catcher Network

Notebook computers equipped with accelerometers can contribute to the Quake-Catcher Network (QCN), a BOINC project aimed at scientific research of earthquakes.
The Quake-Catcher Network is an initiative run by the University of Southern California that aims to use computer-based accelerometers to detect earthquakes.

### Microelectromechanical systems

MEMSmicroelectromechanical systemmicrosystems
Micromachined microelectromechanical systems (MEMS) accelerometers are increasingly present in portable electronic devices and video game controllers, to detect the position of the device or provide for game input. Modern accelerometers are often small micro electro-mechanical systems (MEMS), and are indeed the simplest MEMS devices possible, consisting of little more than a cantilever beam with a proof mass (also known as seismic mass). Damping results from the residual gas sealed in the device. One of the most common uses for MEMS accelerometers is in airbag deployment systems for modern automobiles.
Bulk micromachining has been essential in enabling high performance pressure sensors and accelerometers that changed the sensor industry in the 1980s and 90's.

### Gravimetry

gravimetricgravity measurementsgravimetric devices
Applications for accelerometers that measure gravity, wherein an accelerometer is specifically configured for use in gravimetry, are called gravimeters.
Thus, gravimeters can be regarded as special-purpose accelerometers.

### Smartphone

smartphonessmart phonesmart phones
Some smartphones, digital audio players and personal digital assistants contain accelerometers for user interface control; often the accelerometer is used to present landscape or portrait views of the device's screen, based on the way the device is being held.
Smartphones typically include various sensors that can be leveraged by their software, such as a magnetometer, proximity sensors, barometer, gyroscope and accelerometer, and support wireless communications protocols such as Bluetooth, Wi-Fi, and satellite navigation.

### Noise, vibration, and harshness

NVHnoise, vibration and harshnessNVH (Noise Vibration Harshness)
Another automotive application is the monitoring of noise, vibration, and harshness (NVH), conditions that cause discomfort for drivers and passengers and may also be indicators of mechanical faults.
Typical instrumentation used to measure NVH include microphones, accelerometers and force gauges, or load cells.

This gravity gradiometry is useful because absolute gravity is a weak effect and depends on local density of the Earth which is quite variable.
Accelerometer

### Wii

Nintendo WiiWii miniZii
Nintendo's Wii video game console uses a controller called a Wii Remote that contains a three-axis accelerometer and was designed primarily for motion input.
The Wii introduced the Wii Remote controller, which can be used as a handheld pointing device and which detects movement in three dimensions.

### Thermopile

thermopiles
An accompanying temperature sensor (like thermistor; or thermopile) in the dome is used to determine the temperature profile inside the dome, hence, letting us know the location of the heated bubble within the dome.
Thermopiles are used to provide an output in response to temperature as part of a temperature measuring device, such as the infrared thermometers widely used by medical professionals to measure body temperature, or in thermal accelerometers to measure the temperature profile inside the sealed cavity of the sensor.

### IPod Nano

7th-Generation NanoiPod Nano 4th Generation3g Nano
Apple has included an accelerometer in every generation of iPhone, iPad, and iPod touch, as well as in every iPod nano since the 4th generation.
Also added was an accelerometer which allows the Nano to shuffle songs by shaking it, the option between portrait and landscape display modes by tilting the iPod left or right, and access to Cover Flow when tilted sideways.

Apple has included an accelerometer in every generation of iPhone, iPad, and iPod touch, as well as in every iPod nano since the 4th generation.
The display responds to other sensors: an ambient light sensor to adjust screen brightness and a 3-axis accelerometer to sense iPad orientation and switch between portrait and landscape modes.

### Shock indicator

shock
Single- and multi-axis models of accelerometer are available to detect magnitude and direction of the proper acceleration, as a vector quantity, and can be used to sense orientation (because direction of weight changes), coordinate acceleration, vibration, shock, and falling in a resistive medium (a case where the proper acceleration changes, since it starts at zero, then increases).
They sometimes involve piezo-based accelerometers with low consumption of electrical power.

### Proof mass

seismic mass
Modern accelerometers are often small micro electro-mechanical systems (MEMS), and are indeed the simplest MEMS devices possible, consisting of little more than a cantilever beam with a proof mass (also known as seismic mass). Damping results from the residual gas sealed in the device.
A proof mass that deforms a spring in an accelerometer is sometimes called the seismic mass.

### IPhone

iPhonesiPhone appApple iPhone
Apple has included an accelerometer in every generation of iPhone, iPad, and iPod touch, as well as in every iPod nano since the 4th generation.
A 3-axis accelerometer senses the orientation of the phone and changes the screen accordingly, allowing the user to easily switch between portrait and landscape mode.

### Airbag

airbagsair bagside curtain airbag
One of the most common uses for MEMS accelerometers is in airbag deployment systems for modern automobiles.
The ACU monitors a number of related sensors within the vehicle, including accelerometers, impact sensors, side (door) pressure sensors, wheel speed sensors, gyroscopes, brake pressure sensors, and seat occupancy sensors.

### Piezoresistive effect

piezoresistivepiezopiezoresistor
In commercial devices, piezoelectric, piezoresistive and capacitive components are commonly used to convert the mechanical motion into an electrical signal.
In silicon the piezoresistive effect is used in piezoresistors, transducers, piezo-FETS, solid state accelerometers and bipolar transistors.

### Pedometer

step counternumber of steps takennumber of steps walked
Along with orientation view adjustment, accelerometers in mobile devices can also be used as pedometers, in conjunction with specialized applications.
The 5th and 6th generation iPod Nano by Apple features an integrated accelerometer.

### Inertial footpod

footpodfootpods
Within the last several years, several companies have produced and marketed sports watches for runners that include footpods, containing accelerometers to help determine the speed and distance for the runner wearing the unit.
It uses one or more accelerometers and processes several times a second to compute speed.