Uncertainty Budgets for Comparison Calibrations of Thermocouples

Ripple, Dean C.; Garrity, K. M.

doi:10.1080/19315775.2006.11721305

Cited by 6 publications

(4 citation statements)

References 3 publications

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“…The major contribution to the uncertainty is attributed by inhomogeneity of thermocouple it has been estimated from the immersion/withdrawal thermo-emf profile of thermocouples in fixed point cells, as described in detail before by the authors in other article [4]. The uncertainty due to purity of ingots was evaluated from the manufacturer's certificate stating that for 6/N purity, a repeatable plateau of 1.5 mK can be produced at freezing points [11]. The drift caused in the thermocouple is another component of uncertainty, which was estimated from the earlier fixed point measurements and included in the uncertainty budget.…”

Section: Uncertainty Componentsmentioning

confidence: 99%

Uncertainty evaluation in the calibration of Pt/Pd thermocouples up to copper freezing point at NIS-Egypt

Megahed

Abdelaziz

2011

Int. J. Metrol. Qual. Eng.

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Abstract. The dissemination of traceability to the International Temperature Scale of 1990 (ITS-90) through comparison calibration of thermocouples, is playing an important role in metrology institutes, secondary laboratories and industrial measurements. The previous studies of the Pt/Pd thermocouples at NIS-Egypt, shows promise of achieving significant improvements uncertainty of temperature measurements up to 960 • C. In this paper we describe the uncertainty assessment on the measurements of the calibration of Pt/Pd thermocouples at fixed point cells up to the freezing point of copper and by the comparison technique following a defined heat treatment at 1100 • C. All the measurements on Pt/Pd thermocouples were carried out using NIS facilities.

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Section: Uncertainty Componentsmentioning

confidence: 99%

Uncertainty evaluation in the calibration of Pt/Pd thermocouples up to copper freezing point at NIS-Egypt

Megahed

Abdelaziz

2011

Int. J. Metrol. Qual. Eng.

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“…4, was much better than literature values [5] would suggest. Reference [6] discusses this point further.…”

Section: Discussion Of Resultsmentioning

confidence: 99%

A Regional Comparison of Calibration Results for Type K Thermocouple Wire from (100 to 1,100) °C

et al. 2008

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Under the auspices of the Inter-American Metrology System (SIM), the National Institute of Standards and Technology (NIST) initiated a regional comparison for type K thermocouples from (100 to 1,100) • C with 11 participating countries. The use of type K material above approximately 200 • C is considered destructive. Therefore, each participating laboratory was sent new, unused wire from a lot of material characterized by NIST. The uniformity of the lot was remarkable, especially at temperatures above 500 • C; the standard deviation of the thermocouple emf values of multiple cuts tested at NIST was 2.7 µV or less over the full temperature range. The high uniformity eliminated any need to correct for variations of the transfer standard among the laboratories, greatly simplifying the analysis. The level of agreement among the laboratories' results was quite good. Even though test procedures and equipment varied significantly among the participants, the standard deviation of all emf values at each test temperature was less than the equivalent of 0.20 • C at 200 • C and below, and less than 0.60 • C from (400 to 1,100) • C. Of the 380 total bilateral combinations of the

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“…Certainly, for reference thermocouples complying with the noble-metal letter-designated type definitions (types R, S and B) and the pure-element thermocouples (Au/Pt, Pt/Pd), for which the temperature-induced inhomogeneity effects are smallest and most reproducible, some assessment can be made relatively easily [6]. Uncertainty calculations presented in comparisons suggest it is common to apply a value based on a type B assessment of published data from other studies [7], or data from a representative sample of similar thermocouples [8], rather than data from the device under test (DUT). In many cases it appears likely that inhomogeneity is simply not included in the uncertainty assessment [8,9].…”

Section: Introductionmentioning

confidence: 99%

“…The multi-component alloy compositions of these types endow the thermocouples with a complex metallurgy, which causes an equally complex set of reversible and irreversible changes in Seebeck coefficient [3], some of which will be manifest at temperatures as low as 100 °C [1]. If base-metal thermocouples are calibrated, the introduction of inhomogeneities by the calibration process usually induces such large departures from the as-supplied state as to make the calibration of base-metal thermocouples practically useless, except if the thermocouple is calibrated in situ or used as a representative sample [7]. In some cases, the calibration process induces sufficient change to push the thermocouple outside the limits-of-error tolerance band [1].…”

Section: Introductionmentioning

confidence: 99%

Thermocouple homogeneity scanning

Webster

White

2015

Metrologia

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The inhomogeneities within a thermocouple influence the measured temperature and contribute the largest component to uncertainty. Currently there is no accepted best practice for measuring the inhomogeneities or for forecasting their effects on real-world measurements. The aim of this paper is to provide guidance on the design and performance assessment of thermocouple inhomogeneity scanners by characterizing the qualitative performance of the various designs reported in the literature, and developing a quantitative measure of scanner resolution. Numerical simulations incorporating Fourier transforms and convolutions are used to gauge the levels of attenuation and distortion present in single-and double-gradient scanners. Single-gradient scanners are found to be far superior to double-gradient scanners, which are unsuitable for quantitative measurements due to their blindness to inhomogeneities at many spatial frequencies and severe attenuation of signals at other frequencies. It is recommended that the standard deviation of the temperature gradient within the scanner is used as a measure of the scanner resolution and spatial bandwidth. Recommendations for the design of scanners are presented, and include advice on the basic design of scanners, the media employed, operating temperature, scan rates, construction of survey probes, data processing, gradient symmetry, and the spatial resolution required for research and calibration applications.

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Uncertainty Budgets for Comparison Calibrations of Thermocouples

Cited by 6 publications

References 3 publications

Uncertainty evaluation in the calibration of Pt/Pd thermocouples up to copper freezing point at NIS-Egypt

Uncertainty evaluation in the calibration of Pt/Pd thermocouples up to copper freezing point at NIS-Egypt

A Regional Comparison of Calibration Results for Type K Thermocouple Wire from (100 to 1,100) °C

Thermocouple homogeneity scanning

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