PURPOSE: To attain self-normalization of a solar radiometer by a method wherein a power to be supplied to a heater provided for a thermal guard is controlled so that a difference between the temperature of a blackbody cavity and that of the thermal guard be always zero. ;CONSTITUTION: A temperature difference being proportional to incident energy occurs between a blackbody cavity 3 and a heat sink 5. This temperature difference is outputted by an electromotive force of a thermoelectric pile 6 stuck on the lateral surface of a heat resistor 4. Moreover, a thermal guard 7 is so provided as to surround the cavity 3 and the heat sink 5 is connected also to this guard through another heat resistor 8. When radiation energy enters, the temperature of the cavity 3 becomes higher than that of the guard 7. At the time of measurement, however, a current is made to flow to a heater 9 of the guard 7 to control so that the temperature difference between the cavity 3 and the guard 7 be always zero. The temperature difference between them is detected by a system of a bridge circuit constructed of four ring-shaped temperature-sensitive elements 11.;COPYRIGHT: (C)1993,JPO&Japio
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