Minimum thermometers

From Glossary of Meteorology
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minimum thermometer

A thermometer that automatically registers the lowest temperature attained during an interval of time.

The alcohol-in-glass minimum thermometer contains a dumbbell-shaped index that is kept on the bulb side of the meniscus by surface tension. The thermometer is installed in a horizontal mounting (
see Townsend support) so that as the temperature falls, the index is pulled toward the bulb and remains at the minimum point as the temperature rises. A bimetallic thermometer with a circular dial is also used as a minimum thermometer. A free index, mounted concentrically with and driven by the thermometer index, is held by friction at the minimum temperature.
Compare maximum thermometer.