Accelerometers: What They Are and How Smartphones Use Them

An accelerometer is a device that measures motion and velocity and has multiple applications in engineering, biology, medical sciences, navigation, consumer electronics and transportation. It helps you understand the surroundings of an object so it can be determined if the object is moving upward or downward and whether the object will tip over if it tilts beyond a certain angle.

Accelerometers also are used in smartphones such as the iPhone 5s to measure its orientation and movement in the x-, y- and z-axes. This type of accelerometer is most notably used to rotate the display between portrait and landscape, but it’s also used for other applications as well.

How an Accelerometer Works

A traditional accelerometer has two basic parts: a housing that attaches to the object being measured and a seismic mass that’s tethered to the wall of the housing while still being able to move. When the seismic mass moves inside the housing, it pulls on the tether. Depending on how much the tether is pulled, you can calculate the amount of force applied.

However, accelerometers inside smartphones are a bit more advanced. They are built out of silicon, and the seismic mass is a tiny three-finger, comb-like object. Motion is measured by the direction the silicon fingers are pulled by gravity, and the smartphone is programmed to behave according to different measurements.

How Smartphones Use Accelerometers

Other than determining whether the display should be portrait or landscape, the accelerometer inside your phone can be used with apps that need to measure motion. For example, the accelerometer allows fitness applications to track your distance traveled and number of steps. It’s also the device that lets you play motion-controlled games by measuring how far and how fast you tip and tilt your phone. If you use an application such as Sleep Time or Sleep Cycle, these apps use the accelerometer to track how much you move in your sleep to know the best time to wake you. And, if you ever use your spirit level application while doing construction, that also uses the accelerometer.

The Future of Accelerometers

Even with the incredible technology of the camera, touch sensor and light sensor in smartphones, many experts consider the accelerometer to be both one of the most informative and underused sensors. In the future, you could see more smartphone operating systems and applications better utilizing this technology.

For example, the measurements from an accelerometer could be used to measure different tasks such as walking, jogging, climbing stairs, sitting, standing and lying down. It also could be conceivable to program your phone to send calls directly to voicemail when you’re jogging or to vibrate instead of ringing when you’re lying down. It could have medical uses as well. Researchers at Wireless Sensor Data Mining (WISDM) Lab at Fordham University found it could help users diagnose gait problems, which often point to the existence of additional health problems. And, as more research is done and app developers conceive of new software, the relationship between a phone and its user will become much more intimate and personalized.