A large aperture blackbody (LABB) with a diameter of 1 m has been successfully constructed for calibrating radiation thermometers and infrared radiometers with a wide field of view in the temperature range between 10 • C and 90 • C. The blackbody is a 1 m long cylindro-conical cavity with a diameter of 1.1 m. Its conical bottom has an apex angle of 120 • . To achieve good temperature stability and uniformity, the cavity is integrated to a water-bath to which the pressurized water is supplied from a reservoir. To reduce the convection heat loss from the cavity to the ambient, the cavity is purged of the dried air that passes through a coiled tube immersed in the reservoir. For an uncertainty evaluation of the LABB, its temperature stability was measured by using a reference radiation thermometer (RRT) and a platinum resistance thermometer (PRT), and its radiance temperature distributions on the aperture plane were measured by using a thermal camera. Measuring the spectral emissivity of the coating material, the effective emissivity of the blackbody was calculated to be 0.9955 from 1 µm to 15 µm. The expanded uncertainty of the radiance temperature scale was evaluated based on the PRT readings, which vary from 0.3 • C to 0.5 • C (k = 2) in the temperature range. The temperature scale is validated by comparing with the RRT of which the temperature scale is realized by a multiple fixed-point calibration.
A two-substrate method is developed to simultaneously determine emissivity, transmittance, and reflectance of semitransparent materials with a single measurement under the same environment at elevated temperature. The three quantities can be obtained through the emissivities of substrates and the apparent emissivities resulting from the radiance of the sample heated by substrates. The two-substrate method is compared with the conventional method by measuring sapphire samples with various thicknesses, resulting in good agreements for all the samples. The present method will be useful to measure the temperature dependence of optical properties of porous ceramic materials.
The radiance temperature scale from 500 K to 1,250 K was realized by using a thermal detector transfer reference thermometer (TRT) with its spectral response centered at 3.9 µm. The TRT is calibrated at the four fixed points of tin, zinc, aluminum, and silver, and the scale is obtained by interpolation with Wien's equation, Planck's equation, the Sakuma-Hattori (SH) formula, and a Planckian SH (PSH) formula. The interpolation uncertainty dramatically decreases as the physical model for the interpolation equations becomes more realistic. The uncertainty of the scale is evaluated, including the repeatability of the calibration and the long-term stability of the TRT over a period of more than 20 months. The realized scale over part of the interpolation region was validated by comparing it with the ITS-90, resulting in excellent agreement within 0.09 K. The resulting uncertainty of the realized scale varies from 0.06 K to 0.38 K (k = 1), depending on the temperature.
We present experimental realization and validation of the six-port design of integrating sphere photometers for total luminous flux measurement, which significantly improves the uniformity of spatial response compared to the conventional single-port design. Construction, measurement procedure, and data acquisition of the realized instrument with a radius of 1 m are described. Measurement of the spatial response distribution function confirms the expected effect of improving the uniformity by averaging the signals from the six detection ports. The related spatial mismatch error is determined to be less than 1.4% for all the realistic cases of beam angles and directions of a test lamp mounted in the vicinity of the sphere center. As a result, we confirm that the realized six-port instrument allows us to eliminate the complicated spatial mismatch correction procedure by adding a relative standard uncertainty of only 1.4/3%≈0.81%, which offers a great practical benefit for testing solid-state lighting products of various beam characteristics.
Korea Research Institute of Standards and Science (KRISS) and All-Russian Research Institute for Optical and Physical Measurements (VNIIOFI) conducted a bilateral comparison on spectral irradiance over the spectral region from 250 nm to 2500 nm in 2008. The aim of this comparison was to assess the equivalence of the spectral irradiance scales between the two laboratories and to link the KRISS spectral irradiance scale to the results of key comparison CCPR-K1.a carried out in the years 2000–2003. The technical protocol was approved by the CCPR Working Group on Key Comparisons in April 2008. KRISS acted as the pilot to reduce the workload of VNIIOFI as the link laboratory. PTB acted as the neutral partner to ensure blindness of the comparison results. PTB collected the measurement results from and sent them back to both participants. KRISS prepared this report based on the measurement results distributed by PTB. The spectral irradiances measured by KRISS and VNIIOFI agreed within the standard uncertainties (k = 1) from 250 nm to 2500 nm. The unilateral degrees of equivalence of KRISS were calculated using the unilateral degrees of equivalence of VNIIOFI to link the KRISS spectral irradiance scale to the key comparison CCPR-K1.a. The uncertainties of the unilateral degrees of equivalence of KRISS were determined using the uncertainties of KRISS and VNIIOFI measurements and the uncertainties of the unilateral degrees of equivalence of VNIIOFI, and taking into account the correlation of VNIIOFI measurements between the CCPR key and this bilateral comparison.Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCPR, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).
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