Pressure sensors are one of the most standard and widely used sensor types available. Pressure sensing is ubiquitous in industrial, automotive, and consumer applications.
One challenge with pressure sensors, however, is that these devices often must operate in harsh environments, exposed to high temperatures, high pressures, or water. To make pressure sensing even more reliable and easy to use, STMicroelectronics recently released a new MEMS pressure sensor, which it claims is the industry's first waterproof solution of its kind.
ST's new waterproof MEMS pressure sensor.
Piezoresistive MEMS Pressure Sensors
MEMS technology enables pressure sensing in a number of ways, one of the most common being through piezoresistive sensing. Piezoresistive MEMS pressure sensors work due to the piezoresistive effect, which indicates that a material's electrical resistance changes when it experiences mechanical strain or stress.
To take advantage of this phenomenon, piezoresistive MEMS pressure sensors typically consist of a thin diaphragm or film designed to bend or deform in response to applied pressure. A piezoresistive material is fabricated on the surface of these diaphragms. The deformation of the diaphragm not only causes the strain of the piezoresistive material, but also causes the change of its resistance.
To take advantage of the material's changing resistance, piezoresistive materials are often arranged in a Wheatstone bridge configuration. Here, the constant current or voltage applied to pressure resistance elements, and to measure the resulting voltage or current output. This output is proportional to the applied pressure, allowing pressure measurement.
Generally speaking, the piezoresistive MEMS pressure sensor has the advantages of small size, low power consumption, high sensitivity, and compatibility with integrated circuits. These properties make them suitable for a wide range of applications including automotive, medical, industrial and consumer electronics.
ST Preps MEMS pressure sensors for water resistance are designed for industrial applications.
According to the data sheet, the new pressure sensor (ILPS28QSWTR) supports dual full-scale absolute pressure sensing and is used as a digital output barometer. The two supported user optional modes include Mode 1, which can detect 260 to 1260 hPa, and Mode 2, which can detect 260 to 4060 hPa. The sensor has a low current consumption of 1.7 uA and an absolute accuracy of 0.5 hPa.
The ILPS28QSWTR block diagram.
The industry's first waterproof MEMS with a 10-year lifetime plan, ST says is the pressure sensing solution offered by the ILPS28QSWTR. To achieve this feat, the sensor is housed in a well-designed SMT package that includes a ceramic substrate, potting compound to protect the internal circuitry, and a medical-grade steel cover supported by an epoxy-sealed O-ring.
The package is IP58 certified according to IEC 60529 and ISO 20653 and is guaranteed to enter protection rating, meaning the sensor can withstand immersion in more than one meter of water and withstand overpressure of up to 10 bar.
