Accelerometers in smartphones
With accelerometers, it's all about gravity. Accelerometers are those devices that quantify tilt and motion by measuring acceleration forces. They've been in cars (airbags), planes, industrial machinery, robotics, medical and fitness devices, and famously in laptops (to detect if the device has been dropped), for years. Using its own weight, the accelerometer measures whether it is standing (static) or moving (dynamic) by detecting weight changes from g-force. Some good introductory explanations can be found at LifeScience.com, Dimension Engineering's beginner's guide, and even wikipedia.
The trend now is the accelerometer for smartphones. Accelerometers have traction in devices like no other sensor to this point. "Accelerometers are in every smartphone today," Bouchaud said. "In terms of revenue, the accelerometer market is going to saturate probably this year. The smartphone market has been exploding in China, but in the long run their revenue is also going to go down because the market is saturating." This is very different from compasses, which he pointed out had not achieved 50% penetration in China.
Accelerometers are in more than just smartphones and wearables: They're in phablets and tablets, which are experiencing growth, said Curran, because of the sophistication of the devices. "Accelerometers and gyroscopes are playing a part in that," he said, "One can now easily and seamlessly move from communication mode to a rich media mode also being enabled by these sensors." Accenture’s survey found that more than half of consumers planning to buy a smartphone in the next twelve months indicated they’d prefer a phablet. "A lot of the continuing growth of the category is because its capabilities are continue to expand," he said.
A reference design for ultralow power standalone motion switch from Analog Devices that uses the ADXL362 sensor.
(Source: Analog Devices)
Analog Devices' ADXL362 MEMS sensor
The Analog ADXL362 is, according to Analog's product detail page, an ultralow power, 3-axis MEMS accelerometer that consumes less than 2 μA at a 100 Hz output data rate and 270 nA when in motion-triggered wake-up mode. The device samples the full bandwidth of the sensor at all data rates, unlike accelerometers that use power duty cycling to achieve low power consumption. The ADX 362 accelerates using sample synchronization via external trigger and includes on-chip temperature sensor as well as SPI digital interface. Its measurement ranges are selectable via SPI command. The ADXL362 does not alias input signals by under sampling. The Analog ADX362 comes with an adjustable threshold sleep/wake modes for motion activation The device lowers noise down to 175 √Hz and offers wide supply and I/O voltage ranges of 1.6 V to 3.5 V. It operates off 1.8 V to 3.3 V rails The ADXL362’s ultra-low power can be derived from coin cell battery. It includes high resolution: 1 mg/LSB as well as built-in features for system-level power savings.
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