| 摘要 |
A calibration load that may be used in calibrating a radiometer comprises a hollow disk (16, 18) of thermally conductive material defining a cavity (20), with an aperture (22) at the centre of one face of the disk. The aperture communicates with the cavity and is centred about an axis (11). The cavity (20) is defined between opposed surfaces (16, 18), and it tapers in the direction away from the axis, and these opposed surfaces are covered with radiation-absorbing material. A reflector (24) is arranged such that any radiation that enters the aperture (22) parallel to the axis (11) would be reflected on to a radiation-absorbing surface in the cavity. The reflector (24) may be generally conical. This calibration load (10) provides a black body of the dimensions of the aperture, or of the dimensions of the disk if the outer surface around the aperture is radiation-absorbing.
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