How barometric pressure sensors are ensuring accurate and reliable measurement within industrial applications.
Simply put, barometric pressure is a measurement of the air pressure in Earth’s atmosphere. While scientists and engineers have been using traditional mercury-based barometers to measure barometric pressure since the 1600s, today’s technology has since evolved. Capacitive pressure sensors are now widely used within industrial manufacturing applications to detect pressure changes by monitoring fluctuations in electrical capacitance. xsensor
“In various manufacturing processes, maintaining optimal pressure is essential for ensuring product quality and consistency,” says Jing Lin, product manager, sensors, at Vaisala. “One such example is the semiconductor industry. Our PTB210 and PTB330 barometers are widely used in semiconductor production equipment and are deployed by global leading coater suppliers.”
A coater is equipment used in the photolithography process to apply a thin and uniform layer of photoresist onto semiconductor wafers.
“The air pressure within these systems directly influences film thickness, making precise pressure measurement crucial,” Lin continues. “Vaisala’s barometers have been integrated into coaters to provide accurate air pressure readings, thereby ensuring high product quality.”
First introduced in 1985, Vaisala’s Barocap pressure sensors are developed and designed in-house for barometric pressure measurement applications. In the 40 years since, the sensors have been optimised for various applications in which accurate and stable measurement is required.
“The structure of Barocap is very simple,” says Lin. “It is a micromechanical sensor that uses dimensional changes in its silicon membrane to measure pressure. As the surrounding pressure increases or decreases, the membrane bends, thereby increasing or decreasing the height of the vacuum gap inside the sensor. The opposite sides of the vacuum gap act as electrodes, and as the distance between the two electrodes changes, the sensor capacitance changes. The capacitance is measured and converted into a pressure reading.”
The sensor combines two powerful techniques for barometric pressure measurement: the capacitive sensor principle, and the use of single crystal silicon as the sensor material. “The Barocap sensor’s properties – good elasticity, low hysteresis, excellent repeatability, low temperature dependence, and superior long-term stability – are the result of its single-crystal silicon material,” Lin explains. “The capacitive structure gives the sensor its wide dynamic range and provides a built-in mechanism for overpressure blocking.”
To ensure high quality, the Barocap sensor is manufactured in Vaisala’s own cleanroom, where every assembled barometer goes through a thorough factory testing process covering wide temperature and pressure ranges.
“With the rigorous testing process, we can guarantee high accuracy as well as long term stability over wide and changing environmental conditions,” Lin adds. “This is essential for devices working in harsh outdoor conditions and demanding industrial applications.”
According to Lin, the company’s traceable calibration system also contributes to Barocap’s high performance: “Every Vaisala barometer is individually calibrated in the factory and the measurement results are traceable to the international system of units (SI) through national metrology institutes like NIST USA and VTT MIKES Finland, or via ISO/IEC 17025 accredited laboratories.”
Vaisala’s Measurement Standards Laboratory (MSL) is an ISO17025 accredited calibration laboratory and it maintains traceability and provides high quality calibration services for pressure, temperature, humidity and CO2 concentration.
The lifespan of semiconductor equipment is typically between 10 and 20 years. “Vaisala barometers are extremely stable with typical annual drift of less than 0.1hPa, ensuring accurate and reliable measurements throughout their operational life,” Lin says. “Based on our experience, Vaisala’s barometers generally last between 15 to 20 years in the field, significantly reducing maintenance requirements.”
Aside from semiconductors, another important application area for barometric pressure measurement is the automotive industry, where Vaisala’s pressure instrument is used to measure the inlet air of combustion engines.
Lin explains, “This is an important part in the process of defining engine efficiency and emissions. Car manufacturers are simulating the engine’s performance in different conditions, including altitude simulation and other environmental factors such as humidity and temperature. Vaisala combines pressure, humidity and temperature transmitters such as PTU300 to measure inlet air so that air density, humidity and temperature can be considered.”
The company’s Barocap sensors can also be applied within large marine vessel engine control and emissions optimisation, where the ship engine’s intake air is measured in real-time to optimise the engine performance. “In marine applications, an accurate, robust and reliable instrument that can tolerate harsh conditions such as high humidity and salinity, corrosion and vibration, is crucial,” Lin adds.
The company’s Barocap sensors are not only suited to applications on Earth, as International Design Engineer has previously reported. The Barocap sensors are installed on NASA’s Curiosity and Perseverance rovers, and are still sending data back from Mars after 10 years of operation on the Red Planet.
Looking ahead, Lin says the company plans to continue investing heavily in its research and development activities: “Pressure measurement is one of our core technologies and we will continue our investment in this area to maintain our technology leadership. There are plans to renew our barometer product platforms in the future. For example, the Indigo 500 series transmitter is our latest industrial-grade robust transmitter with modular plug-and-play design and smart sensor features. There will be more exciting new products coming soon.”
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