At the German Aerospace Center (DLR), capacitive humidity sensors are used to measure relative humidity\udin experiments under extreme atmospheric conditions such as on Mars or in the coldest regions on Earth.\udThis raises the question whether such experiments can be performed using low-cost humidity sensors with a\udtolerable measurement uncertainty. As part of the standardizing project SMADLUSEA (project no. SF11021A),\udnine capacitive humidity sensors (Sensirion SHT75) were investigated for pressure ranging from 10 to 1000 hPa\ud(low vacuum) and temperatures from −70 to 25 �C. It has been shown that these sensors worked reliably and\udwith reproducibly measured values over the entire investigated pressure and temperature range. There was no\udaging of the sensors observable. In addition to the known strong temperature dependency, the SHT75 also shows\uda pressure dependency below −10 �C. A characteristic curve for the SHT75 was calculated with an expanded\uduncertainty of 7% of the measured values.\udIn conclusion, low-cost capacitive humidity sensors offer the option to obtain reliably measured values even\udunder extreme conditions with comparatively little effort.
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