Barometric pressure sensor provides indoor location

Pressure sensing is used in the BMP390 barometric pressure sensor which delivers altitude tracking in smartphones, wearable and hearable devices, says Bosch Sensortec.

The sensor can measure height changes below 100mm and is 50 per cent more accurate than its predecessor.

Accurate altitude detection helps to localise people indoors, where GPS signals are not available. Bosch Sensortec has added the vertical-specific position to the existing horizontal information to enable emergency services to determine which level of a building the smartphone user who triggers an emergency call is on. The Federal Communications Commission (FCC) estimates that the additional vertical information has the potential to save up to 10,000 lives per year in the USA alone.

According to a recent report by the FCC, wireless providers in the US will soon be required to meet an increasingly stringent series of location accuracy benchmarks in accordance with a timetable, including providing the caller’s dispatchable location. The order adopts a z-axis location accuracy metric of ±3m relative to the handset for 80 per cent of indoor wireless emergency calls starting in 2021. Emergency applications such as the enhanced 911 (E911) system in the US could also be implemented in Europe or Asia, says Bosch Sensortec.

Bosch and NextNav LLC, a 3D geolocation service provider, have collaborated on component specifications and system performance and believe they have produced high accuracy z-axis capabilities indoors by applying barometric pressure sensors in the phone, combined with NextNav’s Metropolitan Beacon System (MBS) z-axis service to determine three dimensional location and positioning.

The sensor also enables improved indoor navigation in general, for example in combination with the BHI160BP position tracking smart sensor to compensate for traditional localisation technologies such as GPS that do not work efficiently in shielded environments. This will help users to save time and avoid getting lost, for example when searching for a car in an underground garage.

The BMP390 supports enhanced GPS applications for outdoor navigation and calorie estimation tasks. The use of advanced barometric pressure sensing can determine whether a user is walking up or down an incline, up or down stairs or lifting weights during a fitness training session. This helps to increase the precision of calorie tracking by up to 15 per cent Thanks to the improved accuracy of altitude measurements, fitness trackers are able to show exactly how far a user has run, walked or cycled.

The BMP390 provides a typical relative accuracy of ±0.03 hPa, claimed to be superior to any comparable product on the market today. Typical absolute accuracy is ±0.5 hPa; the result of “significant improvements” in temperature stability, drift behaviour and noise, says Bosch Sensortec. The sensor offers high temperature stability across its entire operating temperature and pressure range of 0 to 65 degrees C and 700 to 1100 hPa respectively, with an average temperature co-efficient offset (TCO) of just ±0.6 Pa/K. Noise is also low, at only 0.9 Pa typical, an improvement of 25 per cent relative to the predecessor BMP380 sensor. The device also provides high long-term stability, and low short- and long-term drift.

The BMP390 measures just 2.0 x 2.0 x 0.75mm, making it easy to integrate into portable devices, Bosch points out. Power consumption is low at 3.2 microA at 1.0Hz (typical) to maximise the battery life for portable devices.

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