Miniature water-resistant pressure sensors target wearable apps

As smart watches and wearable fitness trackers permeate the fabric of everyday life, owners want to go further with their devices and track performance across extra activities like swimming. Samsung’s Gear Fit 2 Pro, the next generation of sports band, supports these trends with features like built-in GPS, continuous heart rate monitoring,and larger on-board memory to do more even when not connected to a smartphone. ST’s new waterproof pressure sensor, the LPS33HW, is part of the mix: resistant to chemicals like chlorine, bromine, and salt water, it is ideal for pool or sea swimming, and will also resist soaps or detergents used when showering or cleaning.

Wearables are only just beginning to swim, and waterproofing pressure sensors creates challenges beyond just protecting the electronics. The LPS33HW is not only the most accurate, but also helps OEMs get their products to the store-shelves more quickly by recovering sooner after the stresses of manufacturing. Other sensors can require up to seven days to regain maximum accuracy after coming off the production line, but devices containing the LPS33HW are ready for action in less than half that time. This is due to the sensor’s high-performance built-in processor and the advanced formula of its water-resistant gel filling.

“Wearable trackers enhance smart living, and can now deliver an important extra boost with the go-anywhere ruggedness aided by our water-resistant LPS33HW sensor,” said Andrea Onetti, MEMS Sensor Division General Manager, STMicroelectronics. “Samsung takes advantage of the pressure sensor’s best-in-class performance for the new Gear Fit 2 Pro range and users will appreciate both its accuracy and toughness.”

In addition to smart consumer devices like wearables, other equipment including industrial sensors and utility meters can also benefit from the robustness and high measurement accuracy of the LPS33HW. The 10bar pressure sensor can withstand being submerged up to 90 meters, and the very low RMS pressure noise of 0.008mbar allows apps like an altimeter, depth gauge, or weather monitor to deliver consistent and stable results. The sensor accuracy drifts by less than ±1mbar per year.

When soldered to a circuit board during product manufacture, the accuracy is affected by less than ±2mbar, and returns to normal after less than 72 hours – significantly quicker than similar water-resistant pressure sensors.

The LPS33HW is in production now, in a 3.3mm x 3.3mm x 2.9mm cylindrical metal package suitable for use with O-ring seals, priced from $4.50 for orders of 1000 pieces.