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That accelerometer in your new iPhone 3GS must seem pretty cool, switching the phone to landscape view and steering you through racing games and all. But it's nothing compared with what Hewlett-Packard has come up with.
Accelerometers, or inertial sensors, are devices that sense shocks, vibrations and changes in velocity. The ones used in cell phones and other consumer devices are MEMS (micro-electromechanical systems), essentially integrated circuits with moving parts. Though small and relatively inexpensive, they haven't been able to match the more sensitive sensors used in airliners and other commercial applications until now, according to HP.
Now the company has developed an MEMS accelerometer that can do the work of the high-end sensors, which until now have been mechanical devices the size of a brick that cost about US$1,000 per axis, with each axis sensing motion in one direction. It did so partly with technology developed in its printer division, which uses another type of MEMS in print heads. For now, these HP sensors aren't cheap enough to put in consumer electronics, but because they're MEMS, they may get there in a few years. In the meantime, they could revolutionize the use of accelerometers in buildings and geology.
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Tuesday, March 03, 2009
Single- and multi-axis models are vertical to detect magnitude and direction of the acceleration as a vector quantity, and can be used to sense orientation, vibration and shocks. Accelerometers are present in numerous portable electronic devices and video game controllers, including the Nokia N95, Nokia 5800, Sony Ericsson W910i, Blackberry Storm, Apple iPhone, the Apple iPod Nano 4G and Nintendo's Wii Remote and the Google G1.
Accelerometers may be used in some cases to measure acceleration produced by gravity forces, but only indirectly. This is done by assessing the device's output in situations where gravity forces are known not to vary in time (for example, with the device is at rest at a given altitude), and then inferring from the overall zero vertical acceleration of the device, that the measured non-gravitational forces must be equal (but opposite) to any gravitational fields which are present (see gravimeter).
Accelerometers are also used in inertial navigation systems where the exact gravity is unknown, and then an estimate of the gravity based on the position/altitude is used. This allows the output to be integrated to convert it into changes in vertical velocity and to calculate distance (with respect to the center of the Earth) via essentially dead reckoning.