Water-resistant MEMS pressure sensors meet consumer budgets

Water-resistant MEMS pressure sensors, the LPS33W series from STMicroelectronics, exhibit chemical compatibility, stability, and accuracy for use in applications as diverse as fitness trackers and other wearables, vacuum cleaners, and general-purpose industrial sensing.

The IPx8-rated LPS33W is protected by a viscous potting gel inside the cylindrical metal package to withstand salt water, chlorine, bromine, detergents (such as hand soap and shampoo, e-liquids) and light industrial chemicals such as n-pentane. The package lid provides high corrosion resistance, and the cylindrical form factor is easy to use with o-rings in applications that require a sealed enclosure, says ST.

The proprietary gel formula, together with the built-in signal-conditioning ASIC, ensure class-leading 0.008hPa RMS pressure noise thereby allowing outstanding measurement resolution, claims ST. Susceptibility to reflow-soldering stress during assembly is also extremely low, drifting less than ±2hPa and recovering normal accuracy in 72 hours. This is claimed to be more than twice the speed of other sensors. Temperature compensation keeps accuracy within ±3hPa over the operating range from 0 to +65 degrees C.

The LPS33W operates at just 15 microA in high-performance mode, with a 3.0 microA low-power mode and 1.0 microA power-down to help maximise runtime of battery-powered devices. A 128-bit FIFO stores up to 40 slots of 32-bit pressure and temperature data. This saves power by minimising intervention from the host microcontroller. A low-pass filter and I2C and SPI digital interfaces are also built-in.

The LPS33W is in mass production now, in a 3.3 x 2.9mm cylindrical metal case.

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