Thermo-hygrograph
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A Thermo-Hygrograph is a chart recorder that measures and records both temperature and humidity (or dew point). Similar devices that record only one parameter are a thermograph for temperature and hygrograph for humidity.
A thermograph is usually configured with a pen that records temperature on a revolving cylinder. The pen is at the end of a lever that is controlled by a bi-metal strip of temperature-sensitive metal which bends as the temperature changes.
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