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.

Measurement of the Temperature Using the Tomographic Representation of Thermal States for Quadratic Hamiltonians

The Wigner and tomographic representations of thermal Gibbs states for one- and two-mode quantum systems described by a quadratic Hamiltonian are obtained. This is done by using the covariance matrix of the mentioned states. The area of the Wigner function and the width of the tomogram of quantum systems are proposed to define a temperature scale for this type of states. This proposal is then confirmed for the general one-dimensional case and for a system of two coupled harmonic oscillators. The use of these properties as measures for the temperature of quantum systems is mentioned.

Flux–Profile Relationships in the Stable Boundary Layer—A Critical Discussion

Flux–profile relationships are crucial for parametrizing surface fluxes of momentum and heat, that are of central relevance for applications such as climate modelling and weather forecast. Nevertheless, their functional forms are still under discussion, and a generally accepted formulation does not exist yet. We reviewed the four main formulations proposed in the literature so far and assessed how they affect the theoretical behaviour of the kinematic heat flux (H0) and the temperature scale (T*) in the stable boundary layer, as well as their consequences on the existence of critical values for both the gradient and the flux Richardson numbers. None of them turned out to be fully consistent with the literature published so far, with two of them leading to very unreliable expressions for both H0 and T*. All considered, a convincing description of flux–profile relationships still needs to be found and seems to represents a considerable challenge.

Low Temperature Testing of Ultrasound Sensors in Liquid Nitrogen

Ultrasonic flow metering is one of flow measurement techniques applicable to low temperature environment. Unlike pipe provers or Coriolis mass flowmeters, ultrasonic flowmeters require waveguides in front of ultrasound sensors. The waveguides can prevent heat conduction from the ultrasound sensors to low temperature liquids, such as liquid nitrogen. The ultrasound sensors can maintain its piezoelectricity within the specified temperature ranges by thermal insulation of the waveguides. In this study, low temperature testing on a pair of ultrasound sensors was performed to see if ultrasound waves could be transmitted normally through liquid nitrogen. A flowmeter cell with diameter of 300 mm (equivalently, 12”) was used as a container for liquid nitrogen. Three pairs of ultrasound sensors were installed in the flowmeter cell. Fiber-optic sensors were also attached on its inner wall to measure the temperature of liquid nitrogen. As a result, ultrasound waves were successfully transmitted between a pair of ultrasound sensors by using a preamplifier. The fiber-optic sensors could measure the temperature of liquid nitrogen although the sensors were not calibrated by the reference temperature scale at KRISS.

Analysis of dielectric losses in chromespinelide samples from the ophiolite complexes of the Urals

Relevance is determined by the need to search for scientifically based criteria for the identification of chromite mineralization. The purpose of this work is to study the features of dielectric losses and their temperature dependence of ore-forming chromespinelides in relation to the chemical composition and phase transformations in their structure. Research methodology. To study the dielectric properties of chromespinelides, samples were prepared in the form of a cube with an edge of 0.02 m (two cube samples were prepared from each sample). Measurements were performed in an open system at atmospheric pressure. Dielectric losses were measured with a two-electrode setup every 10 degrees in the temperature range 20–900 °C. Heating rate is 4 deg/min. The temperature in the system was determined with a platinum-piatinum-rhodium thermoeiectric coupie at 0.01 m from the sampie. As a measuring device for determining the tangent of the angie of dielectric losses (tg δ) at alternating voitage, the “Digitai L, C, R Meter” E7-8 was used. The operating frequency of the device is 1 kHz. In the initial sample and the duplicate sampie after its roasting to 900 °C, the content of oxides of ferrous and ferric iron was determined. The reiative change in the ratios of oxide and ferrous iron in the initial sample and in the dupiicate sample after roasting was compared with the position of the maximum dielectric losses on the temperature scale. Results. Samples of chromite ore from various deposits and ore occurrences of the Urals were studied by physical, physicochemical, mineralogical and petrographic methods. The temperature dependences of dielectric losses of 21 samples of chromite ore, consisting of 80–90% of chromespinelides, were obtained. All curves clearly show the maximum dieiectric iosses. This indicates that the losses are of a relaxation nature. The position of the maximum on the temperature scaie is different for the studied chromespinelides and is mainly associated with a change in the ratio H. H value is the relative change in the ratio of oxide and ferrous iron FeO/Fe2 O3 in a chromespinelide sample during its heating to 900 °C. The position of the maximum dielectric losses for the studied samples varies from 450 °C (sampie 1 – massive chromitite from the Podenny mine III deposit – Alapaevsi<y massif) to 842 °C (sample 21 – massive chromite ore from the Tsentrainy deposit – Ray-lz massif). In this case, H vaiue varies from 1.61 to 11.14, respectively. A relationship was revealed between the position of the maximum dieiectric losses on the temperature scale of the studied samples of chromite ore and the parameter H. Conclusions. The above results in combination with other physicochemical parameters can be used as an indicator of a rapid assessment of the type of mineralization.