Sensors & transducers
HOW DO YOU DESIGN SENSORS THAT WORK
ON TWO PLANETS? Humidity and pressure sensors from Vaisala are currently operating in every continent on Earth, as well as on space missions such as NASA’s Curiosity and Perseverance rovers. These motorised vehicles have been
working on Mars since August 2012 and February 2021, respectively, and the technologies in the Vaisala sensors is the same as those deployed in multiple applications on Earth. So, how do you design a sensor that is able to operate in such different environments? We asked Anni Torri, a senior scientist in Vaisala’s Research and Development division.
sensors for two planets, she says: “You don’t… you design sensors that out-perform customers’ needs here on Earth, which means designing for accuracy, stability and longevity. Happily, by developing such high-quality sensors, we also met the requirements of the teams working on the Mars rovers.” Vaisala’s humidity sensor technology HUMICAP was initially launched in 1973, and the BAROCAP pressure sensor followed in 1985. Since that time, Torri says: “The technologies have benefited from continuous improvement, driven by innovation within our team, as well as new and challenging requirements from customers.
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“In addition to the core sensor technology (chip), we have also developed monitoring instruments, transmitters, probes and modules to meet a wide variety of customers’ needs.
ith over 20 years of experience at the company, Anni Torri is well placed to comment. However, when asked how you design
“Applications include meteorological measurements in the extremes of the polar regions and the hottest deserts, as well as industrial operations with a range of conditions. Consequently, the sensors evolved and became able to deliver the highest levels of performance in the most demanding of applications.”
ENVIRONMENTAL MONITORING ON MARS NASA’s Curiosity and Perseverance rovers feature pressure and humidity monitoring devices designed and built by the Finnish Meteorological Institute (FMI). Thanks to the long-term stability and accuracy of these sensors, as well as their ability to tolerate dust and harsh environmental conditions, these technologies are especially suitable for such demanding applications. The FMI devices onboard the rovers employ standard Vaisala HUMICAP humidity sensors and specially customised Vaisala BAROCAP pressure sensors. The modification of the pressure sensor is mainly a slightly thinner membrane to accommodate the lower pressure conditions. In comparison with Earth, Mars is a dry planet; relative humidity is practically zero (0% RH) during the day, and rising during the night as the temperature falls. There have been observations of small amounts of water in the atmosphere in the past, though never in liquid form. Martian surface temperatures vary during the night from
30 February 2023 Instrumentation Monthly
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