Pyrgeometers

Pyrgeometers, instruments used for measuring the intensity of solar radiation. Pyrgeometers are generally called any absolute actinometer used for measuring the energy of direct solar rays. It should be noted that in actinometry there is still no general standard for measuring radiation intensity; there are two scales—the American (Smithsonian Institution) and the European (Ångström). The American scale is 2.25% larger than the European one, which must always be kept in mind when comparing radiation values obtained in different locations. Pyrgeometers for medical purposes are used at resorts for dosing solar radiation in heliotherapy. Pyrgeometers or absolute actinometers are rarely used in resort practice, as they are rather complex instruments requiring special installation, which is not always possible. Therefore, resorts more often use relative actinometers, or as they are more simply called, actinometers. They provide measurements of solar radiation intensity in relative units; to convert the readings of these instruments into absolute units, they must be compared with pyrgeometers (for more details—see Actinometry).