热电偶补偿导线的校准方法

热电偶用补偿导线指在一定温度范围内(包括常温)具有与所配的热电偶的热电动势的标称值相同的一对带有绝缘层的导线,用它们连接热电偶与测量装置,以补偿它们与热电偶连接处的温度变化所产生的误差。所以热电偶补偿导线的准确性直接影响到与热电偶整体测温的准确。     

校准短型廉金属热电偶相关问题的研究

短型廉金属热电偶是一类电极长度较短的可拆卸式廉金属热电偶和廉金属铠装偶的统称。传统的测量设备和测量方法在高温温区往往无法准确测量其示值偏差。通过实验找到其测不准的原因,设计研发接线端恒温器解决这一问题,降低了短型偶示值偏差的扩展不确定度。     

过程校验仪热电偶功能校准方法分析

通常对过程校验仪中具有参考端温度自动补偿的热电偶功能的校准方法常用的有温度校准器法、0℃恒温器法、恒温槽法等三种,文中对参考端温度自动补偿原理和三种校准方法进行了分析。     

Uncertainties in Interpolated Spectral Data

Interpolation is often used to improve the accuracy of integrals over spectral data convolved with various response functions or power distributions. Formulae are developed for propagation of uncertainties through the interpolation process, specifically for Lagrangian interpolation increasing a regular data set by factors of 5 and 2, and for cubic-spline interpolation. The interpolated data are correlated; these correlations must be considered when combining the interpolated values, as in integration. Examples are given using a common spectral integral in photometry. Correlation coefficients are developed for Lagrangian interpolation where the input data are uncorrelated. It is demonstrated that in practical cases, uncertainties for the integral formed using interpolated data can be reliably estimated using the original data.     

Assessment of Uncertainties in Calibration of Langavant Calorimeters

The semi-adiabatic method, commonly referred to as the Langavant method, is widely applied for routine measurements of the hydration heat of cements. This standardized method is applicable to all cements and hydraulic binders, whatever their chemical composition, with the exception of quick-setting cements. The calorimeters used to perform these hydration heat measurements must be previously calibrated by electrical substitution, in order to determine their coefficient of total heat loss \(\alpha \) and their heat capacity \(\mu \) . LNE developed a facility enabling performance of the calibration of these Langavant calorimeters, in order to insure the traceability of the hydration heat measurements to basic quantities such as temperature, time, mass, and electrical quantities. Calibration results of a typical Langavant calorimeter are presented here. The measurement uncertainties of the parameters \(\alpha \) and \(\mu \) have been assessed according to the ISO/BIPM “Guide to the Expression of Uncertainty in Measurement.” The relative expanded uncertainties ( \(k = 2\) ) of the coefficient of total heat loss \(\alpha \) and the heat capacity \(\mu \) are estimated, respectively, to be about 0.7 % and 15 %.     

Microform Calibration Uncertainties of Rockwell Diamond Indenters

National and international comparisons in Rockwell hardness tests show significant differences. Uncertainties in the geometry of the Rockwell diamond indenters are largely responsible for these differences. By using a stylus instrument, with a series of calibration and check standards, and calibration and uncertainty calculation procedures, we have calibrated the microform geometric parameters of Rockwell diamond indenters. These calibrations are traceable to fundamental standards. The expanded uncertainties (95 % level of confidence) are ±0.3 μm for the least-squares radius; ±0.01° for the cone angle; and ±0.025° for the holder axis alignment calibrations. Under ISO and NIST guidelines for expressing measurement uncertainties, the calibration and uncertainty calculation procedure, error sources, and uncertainty components are described, and the expanded uncertainties are calculated. The instrumentation and calibration procedure also allows the measurement of profile deviation from the least-squares radius and cone flank straightness. The surface roughness and the shape of the spherical tip of the diamond indenter can also be explored and quantified. Our calibration approach makes it possible to quantify the uncertainty, uniformity, and reproducibility of Rockwell diamond indenter microform geometry, as well as to unify the Rockwell hardness standards, through fundamental measurements rather than by performance comparisons.     

Calibration of Radiation Thermometry Fixed Points Using Au/Pt Thermocouples

At NMIA, radiation thermometers are calibrated by comparison with a number of reference radiation thermometers which are themselves calibrated using fixed-point cells on the ITS-90 temperature scale (In, Sn, Zn, Al, Ag, and Au). The suitability of NMIA fixed-point cells used for standard platinum resistance thermometers (SPRTs) is evaluated by the comparison of ensembles of cells at each fixed point, and by participation in the international BIPM Key-Comparisons K3 and K4. However, the NMIA fixed-point cells used for radiation thermometry are typically much smaller (only 110 mm in length) and the thermowell length immersed in the metal much shorter (85 mm) than those used for SPRTs. Further, the insulation at the front of the crucible needs to accommodate the F/10 viewing cone of the radiation thermometers, so significant temperature gradients exist near the top of the crucible. As a consequence, the conduction errors obtained using SPRTs are too large to be of practical use. A convenient methodology based on the use of a Au/Pt thermocouple, together with a protective tube assembly to reduce conduction errors, has been developed. This allows the convenient measurement of the phase transition temperature traceable, at the 30 mK level, to the fixed-point cells used at NMIA to realize and maintain the ITS-90 scale. As the measurements are made in situ, the temperature environment, and hence the geometry and formation of the liquid?Csolid interface during melting and freezing, are similar to that occurring when used with radiation thermometers. Results are presented for ITS-90 fixed points up to Ag, establishing formal traceability of radiation thermometry fixed-point cells to NMIA??s primary ITS-90 cells.     

Evaluating the Inhomogeneity of Thermocouples Using a Pressure-Controlled Water Heat Pipe

There exists various research reports concerning the evaluation methods for the measurement uncertainty due to inhomogeneity of thermocouples; however, the universal method is still waiting to be established. This article considers the evaluation methods for the measurement uncertainty due to inhomogeneity of thermocouples based on comparison between results of two measurement methods. The first method is to estimate the uncertainty from the immersion characteristics of a thermocouple within a fixed-point furnace during its realization. The second method is to estimate the uncertainty from the immersion characteristics of a thermocouple within a heat-pipe furnace with a long uniform region. A pressure-controlled water heat-pipe furnace with an immersion depth of 1000?mm is developed to enable this work. It overcomes the technical difficulties that existed in applying conventional sealed heat pipes to such applications. From the immersion characteristics of a thermocouple measured by the above two methods, we have introduced three measurement parameters. Estimating the measurement uncertainty due to the inhomogeneity from our measurement results as examples is discussed.     

Calibration of Thermocouples and Infrared Radiation Thermometers by Comparison to Radiation Thermometry

The National Metrology Institute of Spain (CEM) has designed, characterized, and set-up its new system to calibrate thermocouples and infrared radiation thermometers up to 1600 °C by comparison to radiation thermometry. This system is based on a MoSi₂ three-zone furnace with a graphite blackbody comparator. Two interchangeable alumina tubes with different structures are used for thermocouples and radiation thermometer calibrations. The reference temperature of the calibration is determined by a standard radiation thermometer. Normally, this is used at CEM to disseminate the International Temperature Scale of 1990 (ITS-90) in the radiation range, and it refers to the Cu fixed point. Several noble metal thermocouples and infrared radiation thermometers with a central wavelength near 900 nm have been calibrated, and their uncertainty budgets have been obtained.     

SPRT Calibration Uncertainties and Internal Quality Control at a Commercial SPRT Calibration Facility

The Hart Scientific Division of the Fluke Corporation operates two accredited standard platinum resistance thermometer (SPRT) calibration facilities, one at the Hart Scientific factory in Utah, USA, and the other at a service facility in Norwich, UK. The US facility is accredited through National Voluntary Laboratory Accreditation Program (NVLAP), and the UK facility is accredited through UKAS. Both provide SPRT calibrations using similar equipment and procedures, and at similar levels of uncertainty. These uncertainties are among the lowest available commercially. To achieve and maintain low uncertainties, it is required that the calibration procedures be thorough and optimized. However, to minimize customer downtime, it is also important that the instruments be calibrated in a timely manner and returned to the customer. Consequently, subjecting the instrument to repeated calibrations or extensive repeated measurements is not a viable approach. Additionally, these laboratories provide SPRT calibration services involving a wide variety of SPRT designs. These designs behave differently, yet predictably, when subjected to calibration measurements. To this end, an evaluation strategy involving both statistical process control and internal consistency measures is utilized to provide confidence in both the instrument calibration and the calibration process. This article describes the calibration facilities, procedure, uncertainty analysis, and internal quality assurance measures employed in the calibration of SPRTs. Data will be reviewed and generalities will be presented. Finally, challenges and considerations for future improvements will be discussed.     

低温下微机高精度热电偶温度计标定系统

组建了一套低温下高精度热电偶自动标定系统。该系统结构简单，方便可靠，控温精度为０．０１Ｋ。     

Annealing State Dependence of the Calibration of Type R and Type S Thermocouples

Type R (Pt–13 %Rh versus Pt) and type S (Pt–10 %Rh versus Pt) thermocouples are widely used as reference and working standards for temperature measurements both in calibration laboratories and in industry for temperatures up to 1600 °C. Many laboratories claim that the best achievable uncertainty is 0.1 °C up to 1000 °C and 0.3 °C up to 1550 °C, and international comparisons confirm that this is achievable practically. However, due to (i) preferential Rh oxidation of the Pt–Rh alloy thermoelement and (ii) defect quenching effects, these thermocouples suffer from reversible hysteresis in their calibration. As a result, calibration laboratories usually perform some heat treatment of the wire prior to calibration to attain a specific ‘annealing state’, at which the calibration is performed. Internationally, there are two commonly used annealing states for these thermocouples: the ‘450 °C annealed state’ and the ‘1100 °C quenched state’. High-level comparisons between laboratories in the calibration of type R or type S thermocouples will rigorously specify the annealing state in the protocol, so any systematic differences due to the choice of annealing state will be masked. This article compares the calibration of several thermocouples using the two common annealing states, finding that the difference can be as large as 0.2 °C at 961 °C, larger than the best calibration uncertainties reported. The article examines the advantages and disadvantages to the user of calibrations performed in each state, and the implications for the uncertainty analysis for calibration and use of type R and type S thermocouples.     

Hidden Uncertainties of Temperature Measurements in the Calibration of a Pyrometer

Measurement Techniques - We consider some (earlier neglected) uncertainties of temperature measurements that may appear in the course of calibration of radiation thermometers (pyrometers) aimed at...     

消声室的校准与数据处理

本文主要介绍消声室的定义,用途以及校准方法和用EXCEL表格轻松进行数据处理.     

Model Calibration With Censored Data

The purpose of model calibration is to make the model predictions closer to reality. The classical Kennedy–O’Hagan approach is widely used for model calibration, which can account for the inadequacy of the computer model while simultaneously estimating the unknown calibration parameters. In many applications, the phenomenon of censoring occurs when the exact outcome of the physical experiment is not observed, but is only known to fall within a certain region. In such cases, the Kennedy–O’Hagan approach cannot be used directly, and we propose a method to incorporate the censoring information when performing model calibration. The method is applied to study the compression phenomenon of liquid inside a bottle. The results show significant improvement over the traditional calibration methods, especially when the number of censored observations is large. Supplementary materials for this article are available online.     

检定与校准的区别

本文简单论述计量工作中检定与校准的区别。     

Low-Temperature Drift in MIMS Base-Metal Thermocouples

Inhomogeneities are known to develop within thermoelements exposed to elevated temperatures, resulting in temperature measurement errors. While the Seebeck coefficient drift in base-metal thermocouples due to aging at temperatures over \(200\,^{\circ }\mathrm{C}\) has been extensively investigated, there have been very few investigations into possible Seebeck changes at lower temperatures. Despite warnings about possible effects, most practitioners assume changes in homogeneity are either not significant or not able to develop at temperatures less than \(200\,^{\circ }\mathrm{C}\) . This study reports on measurements of inhomogeneities in base-metal thermocouples arising from heat treatment at temperatures in the region of \(200\,^{\circ }\mathrm{C}\) . Thermoelectric scans of thermocouples were carried out following exposure of a range of mineral-insulated metal-sheathed base-metal thermocouples, from two large manufacturers, of Types E, J, K, N, and T, to either a linear-gradient furnace within the range of \(100\,^{\circ }\mathrm{C}\) to \(320\,^{\circ }\mathrm{C}\) or uniform temperature zones of \(100\,^{\circ }\mathrm{C}\) , \(150\,^{\circ }\mathrm{C}\) , and \(200\,^{\circ }\mathrm{C}\) . The experiments reveal noticeable drift in all base-metal types for temperatures as low as \(100\,^{\circ }\mathrm{C}\) and exposure times as short as 1 h. The most sensitive thermoelement alloys appear to be Constantan, Alumel, and Nicrosil. It is concluded that the common working assumption that base-metal thermocouples suffer no thermally induced changes in the Seebeck coefficient below \(200\,^{\circ }\mathrm{C}\) is false. This observation has significant implications for many high-stability monitoring and control systems reliant on base-metal thermocouples that operate in the range of \(100\,^{\circ }\mathrm{C}\) to \(200\,^{\circ }\mathrm{C}\) . Additionally, thermoelectric scanning of base-metal thermocouples should be carried out at temperatures well below \(150\,^{\circ }\mathrm{C}\) to avoid erasure of strain effects or imprinting of new thermal signatures.