When Temperature and Humidity Levels Matter

This Bluetooth-enabled temperature/humidity data logger is showing its flexible application range by protecting a copy of the Magna Carta.


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The unit allows easy access to temperature and humidity data.

I thought this story was pretty cool both for the technology and the application. Onset, a supplier of data loggers for building performance monitoring, now has its Hobo MX1101 unit (a data logger that measures and transmits temperature and relative humidity data wirelessly to mobile devices via Bluetooth technology) protecting a copy of the Magna Carta.

Originally issued by England’s King John in June 1215 to prevent civil war between the king and his barons, the Magna Carta is a world-famous symbol of justice, fairness, and human rights. Having inspired and encouraged movements for freedom and constitutional government for hundreds of years, the four remaining copies have been awarded “Memory of the World” status by the United Nations Educational, Scientific, and Cultural Organization (UNESCO).

The best-surviving copy of the Magna Carta, currently on exhibition in Britain’s Salisbury Cathedral to commemorate the document’s 800-year anniversary, is stored in a glass display case along with an Onset Hobo MX1101.

“Preserving the text is of paramount importance,” says Emily Naish, archivist at Salisbury Cathedral. “Excessive humidity can cause parchment to buckle as it tries to revert to its natural shape. The parchment can expand while the ink remains static, causing ink to lift from the text. As the room in which the Magna Carta is displayed has large glass windows, it is prone to these kinds of damaging fluctuations in humidity.”

Because the display case is sealed and protected by alarm systems, there was no way to constantly monitor temperature and humidity without going through the time-consuming and complicated process of switching off the alarms and accessing the case.

To address this issue, the Cathedral’s exhibition team installed the data logger. The self-contained wireless unit, which works with Onset’s free HoboMobile app for logger setup and data management, enables staff to use a smart phone or tablet to access the environmental data at any time from a distance up to 100 feet, without having to open the display case.

I have a personal connection with this story because I saw the Magna Carta at Salisbury Cathedral back in 2007 when I was in Great Britain visiting 600 Group. Perhaps an atmospheric data logger such as this unit could make a difference for cleanroom applications or other sensitive quality control environments as well.


Salisbury Cathedral