Realization of a radiation temperature scale from 0 °C to 232 °C by a thermal infrared thermometer based on a multiple-fixed-point technique

A primary temperature scale requires realising a unit in terms of its definition. For high temperature radiation thermometry in terms of the International Temperature Scale of 1990 this means extrapolating from the signal measured at the freezing temperature of gold, silver or copper using Planck's radiation law. The difficulty in doing this means that primary scales above 1000 °C require specialist equipment and careful characterisation in order to achieve the extrapolation with sufficient accuracy. As such, maintenance of the scale at high temperatures is usually only practicable for National Metrology Institutes, and calibration laboratories have to rely on a scale calibrated against transfer standards. At lower temperatures it is practicable for an industrial calibration laboratory to have its own primary temperature scale, which reduces the number of steps between the primary scale and end user. Proposed changes to the SI that will introduce internationally accepted high temperature reference standards might make it practicable to have a primary high temperature scale in a calibration laboratory. In this study such a scale was established by calibrating radiation thermometers directly to high temperature reference standards. The possible reduction in uncertainty to an end user as a result of the reduced calibration chain was evaluated.

Section: Introductionmentioning

confidence: 99%

Potential for improved radiation thermometry measurement uncertainty through implementing a primary scale in an industrial laboratory

Willmott

Lowe

Broughton

et al. 2016

“…The radiant energy exchange through the cavity aperture produces a temperature drop or rise at the cavity bottom, depending on the blackbody temperature with respect to the ambient temperature. The temperature rise ∆T r caused by the radiant heat gain at the TPW temperature can be calculated from the equation [9,37]:…”

Section: Radiant Heat Gainmentioning

confidence: 99%

“…(Hereinafter, the phase transition temperature of a fixed-point will be denoted in brackets). In parallel to other methods [8], the application of the multiplefixed-point method for the realization of the radiation temperature scale below the indium fixed-point promises a great significance for the fundamental metrology [9]. Even though only three fixed-points (mercury (−38.8344 • C), the triplepoint of water (TPW) (0.01 • C) and gallium (29.7646 • C)) are defined in the temperature range of −50 • C to the indium freezing fixed-point temperature [10] in the International Temperature Scale of 1990 (ITS-90), there are several other substances for construction of fixed-point reference sources in this temperature range.…”

Section: Introductionmentioning

confidence: 99%

“…The use of the multiple-fixed-point method for the realization of the radiation temperature scale in the temperature range from 0 • C to 232 • C is reported in [9], where three (Ga, In and Sn (231.928 • C)) fixed-point sources in combination with an ice point (0 • C) based radiator is employed for the calibrations of a TIRT. The fixed-point blackbodies (with an emissivity value of 0.9977 ± 0.0003) have an aperture of 10 mm.…”

Section: Introductionmentioning

confidence: 99%

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A triple point of water cell-based fixed-point blackbody for radiation thermometry

Yurtseven¹,

Uytun²,

Nasibov³

2022

The radiation temperature metrology above 150 °C relies heavily on the use of physical interpolation equations and known reference temperature (provided by solid-liquid phase transition of high-purity metals and metal-carbon eutectic alloys) fixed-point blackbodies. Recent achievements in thermal infrared detector technologies triggered the extension of the scale interpolation below this temperature down to 0 °C by using the reference temperatures provided by Sn, In, Ga fixed-points and ice-point, where the reference temperature of the later is dependent on external parameters. In this work, we demonstrate that the triple-point of water (TPW) based fixed-point blackbody is the metrologically grounded alternative to the ice-point. For this purpose, a fixed-point blackbody, incorporating only a cavity and large area TPW cell (LATPW) was designed, constructed, and validated for the precise calibration of radiation thermometers and thermal cameras at the thermodynamic temperature of TPW. The conceptual design of the LATPW cells is similar to the ones used in contact thermometry, where a thermometer well of the cell is employed as a borehole for a cavity, where the cavity is easily detachable. Four different cavities (two different designs with aperture sizes of 40 mm and 50 mm) and three LATPW cells with two distinct well geometries were comparatively studied in several combinations. The largest absolute temperature difference observed between the primary level reference TPW cell (used in contact thermometry) and the LATPW cells is measured to be only 0.37 mK. Radiometric measurements demonstrate that all radiators maximally reflect the blackbody condition including emissivity close to unity, high uniformity across the aperture and high temporal stability. The simplicity of maintenance and easy in-field usage (only distilled water and dry ice are required) make the TPW blackbodies very versatile for the in-situ calibrations of radiation thermometers and thermal cameras, allowing its application in many areas including clinical environments.

“…However, it is simpler to calibrate the signal response at a few reference temperatures and fit a sensible response model. A commonly used approximation to the Planck law is the Sakuma-Hattori equation ( [16][17][18][19][20]):…”

Section: Device Descriptionmentioning

confidence: 99%

An investigation into a calibration scheme for a light pipe based temperature probe

Olsen

Mathisen

Simonsen

2018

We propose a scheme to ensure traceable calibrations of light pipe based temperature probes. We investigate experimentally and theoretically the properties of a device consisting of a sapphire tube with a tungsten filament at the bottom, filled with an inert gas and sealed to avoid contamination of the filament. The device is used as a contact probe, where the temperature is deduced based on detection and quantification of the Planckian radiation from the filament. The Sakuma–Hattori equation is used to approximate the Planck radiation as a function of temperature, and its parameters are fitted using a small number of calibration points. The impact of a small, temperature dependent emissivity on both the calibration and the interpolation errors is explored, and we find that a dual-band detection scheme is required to reduce the sensitivity to variation in the use conditions.