The Differential Absolute RADiometer (DIARAD) consists of:
- two cavities, one active and one a reference, connected to the same heat sink through heat flux sensors
- two shutters able to expose each cavity or shut them off from solar radiation
This diagram shows how the instrument works by balancing energy received and energy supplied by the Joule effect.
How SOVAP works
- Electrical power is applied to each cavity. The power of the active cavity is controlled to obtain a thermal balance with the reference cavity.
- When open, the active cavity absorbs incident solar energy.
- The cavity’s shutter opens and closes alternately. The reduction in electrical power needed to maintain the balance while the shutter is open is equivalent to the quantity of solar energy absorbed.
- Periodically, the reference cavity is used as an active cavity to validate its characteristics.