| 摘要 |
A calibration standard (C), which is normally attached to an infra-red absorption gauge (H) for the purpose of calibrating the gauge, includes spectrally selective absorption means (E, U, A) having a spectrum closely resembling that of a substance to be measured. The standard also includes diffusing means (U) and a reflective plane (B) for returning infrared radiation, which has passed through the absorption means (E, U, A), to the absorption gauge (H) substantially along the same path as would normally be followed by the radiation reflected from the sample in the absence of the standard. The spectrally selective absorption means (E, U A) is preferably made of inherently anhydrous material, such as glass containing a rare earth substance, or polypropylene, both of which are stable. According to one arrangement, the standard comprises a housing with a window (W) at one end, a plurality of diffusing elements (U) attached to a central portion of the window and a reflective plane (D) spaced from the diffusing elements. The window and/or the diffusing elements and/or the reflective plane may comprise or include the spectrally selective absorption means. |
