Capacitive technology in wearable devices

23rd August 2017

Lanna Deamer

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Datasheet

With more and more applications requiring high accuracy atmospheric pressure data, engineers are seeking ever more sensitive pressure sensing methods. New sensor technologies that are based on capacitive sensing enable engineers to create miniaturised and very accurate devices while satisfying demanding energy constraints and addressing reliability challenges.

By Sampo Härkönen, Senior Manager Pressure Sensor Marketing, Infineon Technologies.

Fitness monitoring wearables are a large part of a growing variety of products and applications require the high accuracy sensing of static and dynamic air pressure.

As these applications are typically found in battery operated devices, it is also essential to combine the high accuracy with optimised low-power operation and reliability across a broad range of operating conditions.

Many existing small form-factor MEMS (Micro Electro-Mechanical System) pressure sensors are built around piezo-resistive measurement techniques. In these cases, the flexing of a diaphragmin relation to changes in pressure is sensed via a strain sensor.

However, piezo-resistive sensing elements are particularly susceptible to variation with temperature changes and they do not respond linearly to temperature.

For this reason, piezo-resistive sensors have a need for more complex calibration compared to a capacitive element.

In addition, resistive measurement can represent a significant drain on power - a particularly important consideration when the target application is battery-powered and operating lifetime is critical.

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