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The intercomparison of radiation temperature scales between PTB and NMIJ was carried out in September 2001. PTB sent their radiation thermometer LP3 to Japan and NMIJ made the comparison between the LP3 and NMIJs Topcon radiation thermometers with a comparison blackbody from 1000/spl deg/C to 2500/spl deg/C. Both scales agreed within /spl plusmn/0.8/spl deg/C in the whole range.
The large area double-heatpipe blackbody (LABB) used for comparing thermodynamic temperatures with the International Temperature Scale of 1990 (ITS-90) at temperatures higher than 600 C is based on two sodium heat pipes. The lowest temperature at which the sodium heat pipes work properly is strongly correlated to the onset of sodium evaporation. This is expected for temperatures well above 500 C. Planning to use the LABB for extending the comparison of thermodynamic temperatures with the ITS-90 to temperatures as low as possible, we measured the isothermal behaviour of the blackbody cavity starting at heatpipe temperatures of 400 C. The temperature of the cylindrical part of the cavity was measured with a standard platinum resistance thermometer (SPRT) sensing the bottom of the cavity and up to three quarter of the cylindrical part of the cavity. The obtained temperature profiles are well explained assuming the occurrence of two superimposing effects: a real nonisothermal behaviour of the LABB for temperatures below 500 C and a cooling of the SPRT caused by radiation loss through the aperture of the cavity. Applying a Monte-Carlo simulation we calculated the emissivity of the LABB at different heatpipe temperatures below 600 C using the obtained non-isothermal temperature distribution at the cylindrical walls. It was found that even at temperatures as low as 415 C the accuracy of the LABB is sufficient for comparison of thermodynamic temperatures and the ITS-90.
For the sake of ensuring improved accuracy and traceability for temperature measurements above the copper point (1084 OC), four laboratories are joining their efforts in developing high-temperature fixed points based on eutectic transitions of metal-carbon mixtures [1]. These phase transitions, on the basis of radiation thermometry results presented thus far [2, 3], encouraged the participants to work towards two eventual applications: hightemperature fixed—point calibration sources for radiation thermometry, and fixed points for the calibration of contact thermometers, including Pt/Pd, Pt/Rh and W/Re thermocouples.
Here will be given the up-to—date works accomplished within or in relation with this project in the participating laboratories. The perspectives of this work are wide and should allow the usage of such fixed points at temperatures ranging from 1150 C to 2700 C. The remaining uncertainty concerns the …
An advanced method for the calibration of tungsten strip lamps is reviewed in detail. The method is based on measuring the ratio of the spectral radiances of two sources at different radiance temperatures TL by radiation thermometry. Instead of using the distribution temperature and the colour emissivity for the calculation of the radiance temperature, the derivative dTL/dλ in the vicinity of the effective wavelength of the detection system is applied. In a first step high-stability vacuum tungsten strip lamps are calibrated as first-order working standards with respect to fixed points of the International Temperature Scale of 1990 (ITS-90). In a subsequent step, secondary working standards are calibrated relative to these first order working standards with light of different wavelengths determined by interference filters. A detailed description of the evaluation procedure for the determination of the radiance temperature of the lamps is given and several problems encountered in operating the lamps are discussed. The standard uncertainties of the radiance temperature are below 0.2 K for the first order working standards.
The Physikalisch-Technische Bundesanstalt (PTB) uses calibrated filter radiometers to measure the thermodynamic temperature of blackbodies applied for the realisation and dissemination of the spectral radiance and spectral irradiance. This paper presents the PTB experience with the stability of the spectral responsivities of two different sets of filter radiometers, a set of four broad-band filter radiometers with centroid wavelengths in the visible spectral range (437 nm, 510 nm, 558 nm and 728 nm), using a combination of coloured glass filters as wavelength selective elements and a set of five narrow-band interference filter radiometers with centroid wavelengths in the visible and in the near infrared wavelength range (676 nm, 802 nm, 903 nm and 1003 nm). The time period of their continuous investigation with respect to the relevant stability parameters, the integrated spectral responsivity and the centroid wavelength, is about seven years for the broad-band filter radiometers and up to ten years for the narrow-band interference filter radiometers. Both types of filter radiometers show sufficient stability for their application as high-accuracy temperature measurement instruments. Relative changes in the integrated spectral responsivity up to some parts in 103 and for the interference filter radiometers a linear increase of the centroid wavelength with time in the order of several ten picometers per year have been observed. A comparison between the two types of filter radiometers is given, with respect to the contribution of the stability of these parameters to the uncertainty budget of thermodynamic temperature determination. Reasons for the observed …
Blackbody radiators provide calculable spectral radiance and irradiance if their temperature and their emissivity is well known. Due to technical restrictions, one single blackbody can cover only a limited temperature range and therefore limited wavelengths for spectral radiance and irradiance calibrations. Space borne instruments for measuring the solar emission usually need calibrations from the UV to the near Infrared part of the optical spectrum [1] whereas remote sensing experiments for measuring earth surface temperatures for climate prediction or spaceborne instruments that deliver evidence for water on the surface of planet Mars [2] require calibration in the far infrared spectral range. To achieve these complementary requirements, PTB has set-up a series of blackbody based instrumentations, which are combined in the Primary Temperature Radiator facility (PriTeRa). To cover the whole wavelength range from 200 nm up to 800 µm different blackbody designs have to be applied.
In order to assess the performance and capability as well as the reproducibility of cell production five different Metal-carbon (MC) eutectic cells from three institutes were measured by radiation thermometry at PTB. The reproducibility of the melting temperature approached the requirements set by CCT/CCPR but significant differences were seen between different manufactures.
The intercomparison of radiation temperature scales between PTB and NMIJ was carried out in September 2001. PTB sent their radiation thermometer LP3 to Japan and NMIJ made the comparison between the LP3 and NMIJ's Topcon radiation thermometers with a comparison blackbody from 1000 C to 2500 C. Both scales agreed within+ 0.8 C in the whole range.