Radiation shield

From Glossary of Meteorology

radiation shield

A device used on certain types of instruments to prevent unwanted radiation from biasing the measurement of a quantity.

The radiation shield for a thermometer, for example, usually consists of a short length of brightly polished metal tubing that encloses the thermosensitive element. The tubing is usually perforated or opened at the bottom to allow proper ventilation and is sometimes artificially ventilated, as in the Assmann psychrometer.