What is a 3D Accelerometer?

Mal Baxter

A three-dimensional (3D) accelerometer is an electromechanical device that detects and measures non-gravitational accelerations. These forces can appear as motion, vibration, or orientation of people or equipment. Such forces include static and dynamic accelerations outside the range of normal gravity. This technology appears in many forms and applications, such as those used in video game controllers, smart phones, or pedometers for testing athletic performance. Accelerometers use three-dimensional axes to measure tilt and motion in physical space and provide a wealth of data for movement analysis, digital information processes, or even mechanical safety measures.

Many modern smartphones contain a 3D accelerometer which allows them to measure motion, and orientation.
Many modern smartphones contain a 3D accelerometer which allows them to measure motion, and orientation.

A 3D accelerometer might measure voltage variances along three perpendicular axes, by the use of flexing silicon fingers, bubble floats, or other techniques. These horizontal, vertical, and depth (X, Y, and Z) axes allow mathematical analysis of gravity (g) forces, or meters per second per second. One g is equivalent to 9.8 meters/second/second, or 9.8 m/s2. Changes in the piezoelectric voltage of crystals, capacitance between microstructures, piezoresistive effects, and even light all allow the electronic processing of physical accelerations. Some accelerometers require calibration in order to set a resting state to zero, which is actually 1 g in Earth's gravity.

3D accelerometers are also used to control the tilt and roll of satellites, in turn accurately adjusting a flight pattern.
3D accelerometers are also used to control the tilt and roll of satellites, in turn accurately adjusting a flight pattern.

Controlling the tilt and roll of satellites and other dynamic high-technology systems, the accelerometer now also operates in a wide range of common products. The technology is used in tablet computers to orient screens, and also to deactivate hard drives to protect circuitry from falls. It measures performance of automobile braking and suspension systems. The technology also serves in vehicle or personal navigation, as well as in the deployment of automobile airbags.

Accelerometers work in camera image stabilization by controlling shutters to minimize motion blur. They control technology from appliances to missile systems. The devices monitor machine and engine vibrations and the gait of runners and walkers. Applications in smart phones and computer tablets allow for new and creative interactions between virtual and physical realities.

A 3D accelerometer may possess either analog or digital outputs, depending upon the technology it will be embedded into. Another usage factor is the number of spatial dimensions required for analysis; for many applications, two dimensions are sufficient for planar measurements from a fixed mount. Additional aspects include sensitivity and maximum swing, or the range of acceleration forces able to be measured. These depend upon the speeds and impacts involved.

Other computational factors include bandwidth, impedance, and buffering issues, all of which affect accelerometer performance. Cost-effective, lower performance accelerometers are increasingly available and serve consumer markets. Highly accurate devices are found in military, government, and laboratory applications.

A tablet computer may use a 3D accelerometer for fall protection.
A tablet computer may use a 3D accelerometer for fall protection.

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