This paper gives the results of an indirect comparison of a cryogenic radiometer from the Institut National de Metrologie (INM), France, and from the Technical Research Centre of Finland (VTT) with a QED-200 from the Van Swinden Laboratorium (VSL), the Netherlands. This comparison was performed at a laser wavelength of 543,515 nm (in vacuum) and at a power level of 100 µW. If this QED-200 is assumed to be stable with time, then two cryogenic radiometers of different design have been shown to agree to 3 × 10-5 with an uncertainty 3 × 10-4 at the 1σ level.
Varpula, T., Touayar, O., Reyn, H., & Bastie, J. (1995). Indirect comparison of cryogenic radiometers from the INM (France) and the VTT (Finland with a QED-200 from the VSL (Netherlands). Metrologia, 32(6), 561-564. https://doi.org/10.1088/0026-1394/32/6/32