CS215 temperature and relative humidity sensor, by Campbell Scientific Ltd, Loughborough, Leicestershire, England, 2010.

For over 150 years, climate scientists have been working to collect regular temperature records close to the Earth’s surface. The CS215 is a digital sensor used for this task. Manufactured by Campbell Scientific Ltd, the CS215 utilises a Sensirion SHT75 relative humidity and temperature element in order to provide accurate and stable measurements of the surrounding environment. For protection, the CS215 can be housed within the MET 20 radiation shield, which is also manufactured by Campbell Scientific. This shield helps to isolate the sensitive elements within the CS215 from moisture and heat, whilst allowing air to flow freely across it. Using these objects, scientists have been able to improve our understanding of the connection between the land and the air above us, providing more thorough and detailed modelling of our atmosphere. The continuity of the ground-based record also helps when analysing longer-term trends relating to climate change, with the earliest daily ground-based measurements dating back to preindustrial times.

The CS215 temperature and humidity sensor consists of an anodised aluminum housing, within which is contained the Sensirion SHT75 element. The element inside is field-replaceable, which helps to eliminate the downtime typically required for recalibration. The CS215 outputs an SDI-12 signal, that is widely measurable by many data loggers.