Bosch Sensortec announces the availability of its first barometric pressure sensor based on the capacitive MEMS technology.

How many calories do you actually burn with strength training exercises like push-ups and pulls-ups? A barometric pressure sensor can help improve the accuracy of fitness trackers, especially in calorie counting applications. 

Bosch Sensortec has launched the BMP581 barometric pressure sensor which it says combines low power consumption with high accuracy for altitude tracking in wearables, hearables, and IoT solutions. This follows the presentation of the BMP580 open-market version at this year’s CES in Las Vegas.  

Until now, Bosch Sensortec has always used piezoresistive technology for its generations of barometric pressure sensors. Based on the specific performance or resolution requirements of its customers, the German company said it has evaluated the best technology to support these applications. “We came to the conclusion that we have more potential to address the performance parameters  with the capacitive sensing technology compared to piezoresistive,” Stefan Finkbeiner, CEO of Bosch Sensortec, told EE Times Europe. “Moving forward, with the need for especially low battery power consumption, we see increased potential in capacitive technology.” 

In comparison to piezoresistive sensors, capacitive sensors offer better performance in motion tracking applications. Advantages include higher accuracy, lower power consumption, better temperature stability, and low pressure noise. 

With the BMP581, Bosch claims a new MEMS technology in a new ASIC package design. “In our market segment, it’s either piezoresistive or capacitive, and then you have to make the best out of the technology and the best design […] to meet the performance parameters,” he continued. 

Bosch Sensortec uses capacitive technology for its inertial sensors and says it has drawn on its experience for the ASIC design of its barometric pressure sensors (e.g., How to make it power efficient? How to evaluate capacitive signals? How to have good control over instabilities?).

Compared to its previous generations of piezoresistive sensors, and the BMP390 in particular, the BMP581 is claimed to bring further improvements to key performance parameters. 

Bosch Sensortec outlined that its BMP581 has improved the current consumption by 85% to 1.3 µA, the noise by 80% to 0.08 Pa, and the temperature coefficient offset (TCO) by 33% to ± 0.5 Pa/K. 

The BMP581 provides a relative accuracy of 0.6 hPa and an absolute accuracy of 0.3 hPa, the company stated.

To better visualize the accuracy, Finkbeiner said the BMP581 can measure a fluctuation in barometric pressure equivalent to one-thousandth the weight of a mosquito (circa 7.6mg). 

With the BMP581, Bosch Sentortec sees potential beyond smartphones and targets wearables and hearables, as well as smart home, IoT and industrial applications. 

“These devices are already in a lot of phones right now, but the pressure sensor is going more and more in wearables where power consumption, noise and performance accuracy count,” said Finkbeiner. “The biggest potential right now is in the wearable segment.” 

Talking more specifically about fitness monitoring, he said the altitude tracking capability can provide “a better calorie counting,” because the calories differ greatly if you walk or run on a flat surface or if you climb stairs or a steep mountain path. The same precision is required when doing pull-ups or push-ups.

The BMP581 is also claimed to improve the flight stability and landing accuracy of drones, and help detect water levels in appliances to prevent flooding. And since the sensor detects an altitude change of just a few centimeters, Bosch Sensortec said it can help rescue teams identify the floor and locate people in case of emergency. 

There can be some protection on the sensor die, but “if you want to operate in harsh environments, you may need additional protection,” Finkbeiner specified. “There are sensors in the former generations where there is a shell on top of the sensors. We don’t have it for this product. We could think about doing this for variants in the future.” 

The BMP581, available in a 2.0mm x 2.0mm x 0.75mm3 metal package, is in mass production. 

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Anne-Françoise Pelé is editor-in-chief of EE Times Europe.

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