STMicroelectronics Debuts ‘First’ Waterproof MEMS Pressure Sensor
A new waterproof sensor from ST promises precision in gas- and water-metering equipment, weather monitoring, air conditioning, and home appliances.
Pressure sensors are one of the most standard and universally applied types of sensors available. Across industrial, automotive, marine, and consumer applications, pressure sensing can be found just about anywhere.
One challenge with pressure sensors, however, is that these devices often must operate in harsh environments—designs exposed to high temperatures, intense pressure, or water. To make pressure sensing more reliable and accessible, STMicroelectronics recently released a new MEMS pressure sensor it claims is the industry’s first waterproof solution of its kind.
ST's new waterproof MEMS pressure sensor. Image courtesy of STMicroelectronics
Piezoresistive MEMS Pressure Sensors
MEMS technology can achieve pressure sensing in several ways, and one of the most common is through piezoresistive sensing. Piezoresistive MEMS pressure sensors can operate because of the piezoresistive effect, which states that the electrical resistance of a material changes when it experiences mechanical strain or stress.
To exploit this phenomenon, a piezoresistive MEMS pressure sensor generally consists of a thin diaphragm or membrane designed to flex or deform in response to applied pressure. Fabricated on the surface of these diaphragms are piezoresistive materials. The deformation of the diaphragm causes strain on the piezoresistive materials, leading to a change in its electrical resistance.
Piezoresistive materials in a Wheatstone bridge configuration. Image courtesy of Avnet
To make use of the changing resistances of the material, the piezoresistive materials are typically arranged in a Wheatstone bridge configuration. Here, a constant current or voltage is applied to the piezoresistive elements, and the resulting voltage or current output is measured. This output is proportional to the applied pressure, allowing for pressure measurement.
In general, piezoresistive MEMS pressure sensors offer several advantages, including small size, low power consumption, high sensitivity, and compatibility with integrated circuits. These features make them suitable for a wide range of applications, including automotive, medical, industrial, and consumer electronics.
ST Preps MEMS Pressure Sensor for Water Exposure
Recently, STMicroelectronics announced the release of a new piezoresistive-based MEMS pressure sensor designed for industrial applications.
According to the datasheet, the new pressure sensor (ILPS28QSWTR) operates as a digital output barometer that supports dual full-scale absolute pressure sensing features. The two supported user-selectable modes include Mode 1, which senses from 260 ~ 1260 hPa, and Mode 2, which senses from 260 ~ 4060 hPa. The sensor features an absolute accuracy of 0.5 hPa and a current consumption as low as 1.7 uA.
The ILPS28QSWTR block diagram. Image courtesy of STMicroelectronics
ST claims the ILPS28QSWTR is the industry’s first waterproof MEMS pressure sensing solution with a declared 10-year longevity program. To achieve this feat, the sensor comes in a tightly-designed SMT package, including a ceramic substrate, a potting gel to protect the internal circuitry, and a lid made from surgical steel that is supported by an epoxy-sealed o-ring.
This package secures an ingress-protection rating and achieves IP58 certification according to IEC 60529 and ISO 20653. This certification means the sensor can withstand immersion in over one meter of water and sustain up to 10 Bar overpressure.