actinometric instrument for measuring the balance of radiation (the difference between the inflow and outflow of radiant energy) of the earth’s surface or any point in the atmosphere. Many designs exist, but the most common is the thermoelectric balance meter of Ianishevskii. Its receiving part consists of two thin, horizontal copper plates with blackened outside surfaces; one takes in radiation coming from the sun and the upper strata of the atmosphere, while the other takes in radiation from the earth’s surface and the lower strata of the atmosphere and reflected radiation. Thermoelements are attached to the internal surfaces of the plates to measure the difference in their temperatures. The difference in the temperatures of the plates proportional to the difference in the flows of radiant energy is measured by the force of the thermoelectric current. In compensating balance meters, in order to even out the temperatures of the plates, an electric current is passed through the colder plate, heating it; the balance of radiation is determined by the force of the current.
G. N. KOSTIANOI