One of the biggest questions that a wearable Health Tech device can ask is “Where am I?” Depending on the application, changes in location can make a big difference; did the wearer just go upstairs or downstairs to another level in the building? Is the user’s hand higher or lower than it was a fraction of a second ago, signaling some gesture to control a device? Design engineers use some very clever logic to correlate data from a variety of devices to help keep track of the device’s location in three-dimensional space.
One component in their back of tricks is the barometric pressure sensor. Air has mass and the higher up you go, there’s less air pressing down on you. Measuring that difference can indicate how much you have gone up or down. One manufacturer of such devices, Infineon, has just announced a new barometric pressure sensor for wearable applications. The tiny 2 x 2.5 x 1 mm chip contains a microelectromechanical (MEMS) device that accurately measures tiny pressure changes. It uses a capacitive technology instead of the usual piezoelectric design. It can measure differences in altitude as small as about two inches.
The device also requires very little power. It only draws 3 uA when recording measurements once a second, and less than 1 uA when idle. It also has integrated memory that can store the past 32 measurements so that the controlling device does not need to wake up to poll it for every measurement interval.
Devices like this will help make the next generation of wearable Health Tech devices possible, not to mention smaller, less costly, more energy efficient, and more accurate.
