An online accessible paper by:
M. R. Dury1, T. C. Arneil2, G. Machin1 and T. M. Goodman1
1-National Physical Laboratory, Teddington, United Kingdom
2- University of Cambridge, Cambridge, UK
When performing high accuracy radiation thermometry, the size-of-source effect (SSE) of a filter radiometer can provide a significant contribution to the uncertainties associated with the measurements.
During the development of a new filter radiometer, the THermodynamic Optical Radiometer (THOR), which we designed specifically to measure the melting points of High Temperature Fixed Point (HTFP) cells, indirect SSE measurements were performed on a prototype instrument to aid selection of optical components and their optimum positions with the aim of minimising its SSE.
We performed tests to choose the objective lens, and to understand the effects of the collimating lens.