Realisation of the ITS-90 and thermodynamic temperature measurements above 960 °C using a monochromator-based radiance comparator

At LNE-Cnam, the International Temperature Scale of 1990 (ITS-90) and thermodynamic temperature measurements above the silver point, are carried out with a radiance comparator. This instrument is, more generally, devoted to any radiance comparison in temperature range from the ambient to 3000 °C. The instrument developed in the early 1990s at LNE-Cnam has the advantage of being completely adjustable. Compared to compact radiation thermometers based on lenses and a narrow-band interference filter, the radiance comparator is only made of gold coated mirrors and a Czerny-Turner monochromator to select the spectral bandwidth. The instrument offers the possibility to tune the geometric extent and the slit scattering function. In return, the radiance comparator is a complex instrument that requires a complete and a regular characterisation at the highest level of accuracy. In the first part, this paper describes the instrument and its operating principle. In a second part, a complete study of the wavelength calibration, the slit scattering function, size of source effect, out-of-band transmittance, linearity and other main sources of uncertainty are presented and discussed. Their associated uncertainties are estimated separately and are grouped together to give an example of propagation of uncertainties when performing the ITS-90.

The Efficiency of the Chinese Silver Standard, 1920–1933

We test for integration of financial markets in China during 1920-1933 using a new dataset of domestic exchange rates. Our data concerns tael-denominated telegraphic transfers between Shanghai and nine other cities. We find that Chinese financial markets, as measured by the efficiency of silver-point arbitrage, were highly integrated among major commercial hubs in north and central China, but there was a lower level of integration for more remote cities in the south. Our paper presents the first comprehensive assessment of the efficiency of the Chinese silver standard and contributes to a revaluation of market performance during pre-communist China.

Thermodynamic temperature by primary radiometry

Above the freezing temperature of silver (1234.93 K), the International Temperature Scale of 1990 (ITS-90) gives a temperature, T 90 , in terms of a defining fixed-point blackbody and Planck's law of thermal radiation in ratio form. Alternatively, by using Planck's law directly, thermodynamic temperature can be determined by applying radiation detectors calibrated in absolute terms for their spectral responsivity. With the advent of high-quality semiconductor photodiodes and the development of high-accuracy cryogenic radiometers during the last two decades radiometric detector standards with very small uncertainties in the range of 0.01–0.02% have been developed for direct, absolute radiation thermometry with uncertainties comparable to those for the realization of the ITS-90. This article gives an overview of a number of design variants of different types of radiometer used for primary radiometry and describes their calibration. Furthermore, details and requirements regarding the experimental procedure for obtaining low uncertainty thermodynamic temperatures with these radiometers are presented, noting that such radiometers can also be used at temperatures well below the silver point. Finally, typical results obtained by these methods are reviewed.