Comparison System for the Calibration of Capsule-Type Standard Platinum Resistance Thermometers at NMIJ/AIST

A new comparison system has been constructed using a Gifford- McMahon type cryogenic refrigerator for the calibration of capsule-type standard platinum resistance thermometers (CSPRTs) below 273.16 K at the National Metrology Institute of Japan (NMIJ). The system can compare six CSPRTs at once. A gold-plated comparison block, in which CSPRTs are mounted for calibration, is made from oxygen-free high-conductivity copper. The standard uncertainties related to the temperature control of the system are estimated to be 0.04 mK. The calibrated values for CSPRTs and a rhodium–iron resistance thermometer obtained using the comparison system are in good agreement with those obtained by the direct realization of the low-temperature fixed points of the ITS-90 within the combined standard uncertainty for the calibration using the comparison system.     

Methods of Constructing an Individual Calibration Characteristic for Working Platinum Resistance Thermometers

Methods recommended for calibrating working platinum resistance thermometers are considered. A simplified method of constructing an interpolation curve in the form of second- and third-degree polynomials, calculated from the results of a calibration of thermometers at fixed points of the temperature scale, is proposed and investigated. It is shown that the error of the method lies within the limits of the error of temperature measurements made with working resistance thermometers in the 0–660°C range.     

薄膜铂热电阻特性分析

薄膜铂电阻在温度测量领域应用广泛,使用数量巨大。在很多行业中,已取代了传统的线绕式铂电阻,但由于其原理未被充分掌握,以及特性未被深刻认识,在使用过程中,实际性能指标常常不理想,其高精度和高稳定性未得到充分发挥。为此对薄膜铂电阻工作原理、结构和加工工艺进行了介绍、针对不同于传统铂电阻的电阻温度变化规律、热响应时间和自热效应的特性进行分析,对在开展高精度温度测量应用时需注意的问题予以说明。     

Estimation of Uncertainty in the Calibration of Industrial Platinum Resistance Thermometers (IPRT) Using Monte Carlo Method

Monte Carlo method has been implemented for uncertainty estimation in IPRT calibration. The work is based on the Callendar van Dusen equation for 0–500 °C calibration range. Derivation of the mathematics model for running the simulation is also described. Results are compared with output from the traditional GUM method and we find close agreement between two methods.     

Thermal Hysteresis in Thin-Film Platinum Resistance Thermometers

Thin-film platinum resistance thermometers (PRTs) are generally manufactured using the deposition of a thin platinum film on an alumina substrate and a laser-trimming method. Because of the strong adhesion between the platinum thin film and the alumina substrate, the PRTs inevitably have strain over the operating temperature range. This causes anomalies and instabilities in the resistance versus temperature characteristics (R?CT). The most prominent and observable effect of thermally induced strain is the thermal hysteresis in the R?CT characteristics. Thermal hysteresis is one of the main uncertainty factors in the calibration of industrial platinum resistance thermometers in laboratories. The thermal hysteresis for 30 thin-film PRTs was measured in the range of 0 °C to 500 °C in 100 °C steps. The thermal hysteresis was measured repeatedly using the same process, and the hysteresis decreased drastically with the repeated measurements. The thermal hysteresis was distributed from 16 mK to 156 mK for all sensors, and the lowest hysteresis was 1 mK to 11 mK in the test temperature range.     

Uncertainty Evaluation and Validation of a Comparison Methodology to Perform In-house Calibration of Platinum Resistance Thermometers using a Monte Carlo Method

The uncertainty required by laboratories and industry for temperature measurements based on the practical use of platinum resistance thermometers (PRTs) can commonly be achieved by calibration using temperature reference conditions and comparison methodologies (TCM) instead of the more accurate primary fixed-point (ITS-90) method. TCM is suitable for establishing internal traceability chains, such as connecting reference standards to transfer and working standards. The data resulting from the calibration method can be treated in a similar way to that prescribed for the ITS-90 interpolation procedure, to determine the calibration coefficients. When applying this approach, two major tasks are performed: (i) the evaluation of the uncertainty associated with the estimate of temperature (a requirement shared by the ITS-90 method), based on knowledge of the uncertainties associated with the temperature fixed points and the measured electrical resistances, and (ii) the validation of this practical comparison considering that the reference data are obtained using the ITS-90 method. The conventional approach, using the GUM uncertainty framework, requires approximations with unavoidable loss of accuracy and might not provide adequate uncertainty evaluation for the methods mentioned, because the conditions for its valid use, such as the near-linearity of the mathematical model relating temperature to electrical resistance, and the near-normality of the measurand (temperature), might not apply. Moreover, there can be some difficulty in applying the GUM uncertainty framework relating to the formation of sensitivity coefficients through partial derivatives for a model that, as here, is somewhat complicated and not readily expressible in an explicit form. Alternatively, uncertainty evaluation can be carried out by a Monte Carlo method (MCM), a numerical implementation of the propagation of distributions that is free from such conditions and straightforward to apply. In this paper, (a) the use of MCM to evaluate uncertainties relating to the ITS-90 interpolation procedure, and (b) a validation procedure to perform in-house calibration of PRTs by comparison are discussed. An example illustrating (a) and (b) is presented.     

高温铂电阻温度计工作基准装置

本文介绍了高温铂电阻温度计、工作基准装置及其相关要求、复现方法。     

Characterization of High-Temperature Platinum Resistance Thermometers at Silver Point

Thermal cycling tests have been conducted on various types of high-temperature standard platinum resistance thermometers (HTSPRTs) that are commercially available at present. The investigated HTSPRTs have nominal resistance values at the triple point of water (TPW) of 0.25 \(\Omega \), 0.6 \(\Omega \), 2.5 \(\Omega \), and 3 \(\Omega \). They vary in terms of the platinum wiring on their sensor supports (frames) and the support materials, their protective sheaths and their sealing materials. Ten HTSPRTs were evaluated with regard to their stability during use at silver-point temperature or above. This evaluation included a thermal cycling test following various setup patterns, which indicated that each HTSPRT has its own preferred pattern. The stability test results for eight of ten HTSPRTs during four silver-point realizations, based on this pattern, yielded a maximum discrepancy in the resistance ratio of within \(\pm 6\,\hbox {mK}\). The maximum resistance discrepancy at TPW was \(\pm 2.7\,\hbox {mK}\).     

高温铂电阻温度计工作基准装置

本文介绍了高温铂电阻温度计、工作基准装置及其相关要求、复现方法。     

Evaluation of Small-Sized Platinum Resistance Thermometers with ITS-90 Characteristics

Many platinum resistance thermometers (PRTs) are applied for high precision temperature measurements in industry. Most of the applications use PRTs that follow the industrial standard of PRTs, IEC 60751. However, recently, some applications, such as measurements of the temperature distribution within equipments, require a more precise temperature scale at the 0.01 °C level. In this article the evaluation of remarkably small-sized PRTs that have temperature?Cresistance characteristics very close to that of standard PRTs of the International Temperature Scale of 1990 (ITS-90) is reported. Two types of the sensing element were tested, one is 1.2 mm in diameter and 10 mm long, the other is 0.8 mm and 8 mm. The resistance of the sensor is 100 ?? at the triple-point-of-water temperature. The resistance ratio at the Ga melting-point temperature of the sensing elements exceeds 1.11807. To verify the closeness of the temperature?Cresistance characteristics, comparison measurements up to 157 °C were employed. A pressure-controlled water heat-pipe furnace was used for the comparison measurement. Characteristics of 19 thermometers with these small-sized sensing elements were evaluated. The deviation from the temperature measured using a standard PRT used as a reference thermometer in the comparison was remarkably small, when we apply the same interpolating function for the ITS-90 sub-range to these small thermometers. Results including the stability of the PRTs and the uncertainty evaluation of the comparison measurements, and the comparison results showing the small deviation from the ITS-90 temperature?Cresistance characteristics are reported. The development of such a PRT might be a good solution for applications such as temperature measurements of small objects or temperature distribution measurements that need the ITS-90 temperature scale.     

二等标准铂电阻温度计标准装置不确定度分析

本文是对二等标准铂电阻温度计标准装置不确定度进行表示和评定。在实际运用中应注意人员、标准、环境、方法等不确定度分量进行评定。不确定度是测量工作的质量和测量结果可信赖程度和评价。按JJF1059-2012、JJG229-2010标准规定,对我单位的标准装置不确定度进行了详细分析,并按JJF(军工)3-2012要求对计量标准进行了重复性和稳定性考核,最后给出了计量标准装置不确定度评定。     

Calibration of Industrial Platinum Resistance Thermometers up to 700\,^{\circ }\mathrm{C}

Industrial grade platinum resistance thermometers were calibrated in the temperature range from \(200\,^{\circ }\mathrm{C}\) to \(700\,^{\circ }\mathrm{C}\) . Both wire-wound and thin-film sensor-based thermometers were investigated. The purpose of the study was to investigate thermometers which could be used in future coal power plants. The calibrations were performed in a vertical cesium heat-pipe furnace and in a horizontal and vertical sodium heat-pipe furnace. The reference thermometer was a standard platinum resistance thermometer calibrated at fixed points up to the aluminum point. In addition to calibration, various thermal tests including immersion measurements and thermal-cycling tests were performed. The stability of the sensors was determined by monitoring the ice-point resistance. Possible contamination of the sensors was determined by measuring the resistance ratio \(R(30\,^{\circ }\mathrm{C})/R(10\,^{\circ }\mathrm{C})\) several times during the measurement period. The calibration curves were compared with the ICE 60751 standard and International Temperature Scale 1990 (ITS-90) reference functions. Considerable changes were found in all tested thermometers. The wire-wound sensors were more stable than the thin-film sensors.     

Stability of Standard Platinum Resistance Thermometers and Rhodium Iron Resistance Thermometers for the Past Decade in NMIJ/AIST

In this study, the stability of four capsule-type standard platinum resistance thermometers (CSPRTs) has been checked by evaluating behavior of the calibrated values at each cryogenic fixed point of the International Temperature Scale of 1990 (ITS-90) below 273.16 K since around 2005. Performance of three capsule-type RhFe resistance thermometers (RIRTs) has been also observed at the triple points of Ne and \(e\hbox {-}\hbox {H}_{2}\). It is confirmed that CSPRTs and RIRTs are stable within the uncertainty of calibration at each low-temperature fixed point for a past decade except for one CSPRT. The resistance of the CSPRT was clearly affected by the accidental mechanical shock at TPW, although the variation of its calibration values was unclear at the triple points of Ar, \(\hbox {O}_{2}\) and Ne and was still within the uncertainty at the triple points of Hg and \(e\hbox {-}\hbox {H}_{2}\). And the CSPRT shows stable behavior after re-calibration again.     

Approximating the ITS-90 Temperature Scale with Industrial Platinum Resistance Thermometers

Platinum resistance thermometers (PRTs) are widely used for accurate temperature measurements in industrial process control as well as in testing and calibration laboratories. Industrial-type PRTs (IPRTs) are available with platinum wires of different purity and can attain measurement accuracy at the level of few tens of millikelvin in a broad temperature range from −196 °C to 550 °C and above. For such IPRTs, the most-used interpolation model (resistance versus temperature) is based on the Callendar–Van Dusen (CVD) equation, which is also recognized in several industrial standards including IEC 60751 and the corresponding national standards. In recent years, several studies have shown that systematic differences exist between the ITS-90 temperature (T ₉₀) and the temperature calculated by the CVD function. When the CVD equation is used to fit experimental data, the difference can be as large as several tens of millikelvin, even near a calibration point, i.e., of the same order of magnitude as the experimental uncertainty routinely achieved in laboratory calibrations. In order to overcome the above limitations, many interpolation models were proposed. The aim of this work is to assess the use of ITS-90 defining equations in precision laboratory calibrations of IPRTs in the temperature range from  −196 °C to 420 °C. Twenty IPRTs with W(100) ranging from 1.384 to 1.392 were calibrated by comparison against a standard PRT, and the experimental data were processed using several interpolation schemes based on ITS-90 deviation functions with different degrees of freedom. The overall results showed that any ITS-90-based scheme performs better than the CVD equation, suggesting that it be applied to a broad spectrum of industrial and laboratory applications.     

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.     

Uncertainty Propagation for Platinum Resistance Thermometers Calibrated According to ITS-90

A new supplement to the GUM outlines uncertainty calculations using matrix algebra for models with more than one output quantity. This technique is applied to the problem of uncertainty propagation for platinum resistance thermometers (PRTs). PRTs are calibrated at specified sets of defining fixed points dependent on the desired temperature range. The problem of uncertainty propagation from the fixed-point calibration results plus the resistance of the PRT in use as input quantities to the coefficients of the deviation function as intermediate results and the temperature as a sole output quantity is discussed. A general solution in matrix form for any temperature range of the ITS-90 defined by PRTs is highlighted. The presented method allows for an easy consideration of the input quantity correlations, which differ with the circumstances of the accomplishment of the fixed-point calibrations and the resistance measurement of the thermometer in use. An example calculation for a specific temperature range based on a simplified model for the input quantity correlations demonstrates this benefit.     

Comparison of Blackbodies for Calibration of Infrared Ear Thermometers

The article presents the results of the EURAMET Project No. 927 ??Comparison of blackbodies for calibration of infrared ear thermometers (IRETs)??. The objective of the comparison was to determine the agreement of blackbodies used for the calibration of IRETs among European national laboratories. To verify the accuracy of an IRET, a suitable blackbody (BB) is needed. Such a blackbody related to the EN standard, designed for the calibration of ear thermometers and immersed in a stirred water bath, was provided for the comparison by the pilot laboratory. The pilot provided also the transfer IRET and organized the comparison.     

检定工业铂、铜热电阻应注意的问题

本文对新规程JJG229-2010《工业铂、铜热电阻》在具体实施过程中应注意的问题提出解决方法,以便能够更好的执行新规程。     

Bilateral Comparison of Aluminum Fixed-Point Cells Using Standard Platinum Resistance Thermometer

The objective of Project EURAMET 1114 (Bilateral comparison of a freezing point of aluminum) in the field of thermometry is to compare realization of a freezing point of aluminum (660.323???C) between the Dutch national laboratory VSL and the Slovenian national laboratory MIRS/UL-FE/LMK using a long-stem 25 ?? standard platinum resistance thermometer (SPRT). Both laboratories had participated in a number of inter-comparisons on the level of EURAMET and also on BIPM CCT level (VSL). MIRS/UL-FE/LMK laboratory recently acquired a new fixed-point cell which had to be validated in the process of intercomparison. A quartz-sheathed SPRT was selected and calibrated at MIRS/UL-FE/LMK at the aluminum freezing point and at the water triple point. A second set of measurements was made on the same SPRT and at the same fixed points at VSL (NL). After its return, the SPRT was again recalibrated at MIRS/UL-FE/LMK. In the comparison the W value of the SPRT was used. The results of the internal and external intercomparisons confirmed that the new aluminum cell of the MIRS/UL/FE-LMK realizes a temperature that agrees with the VSL aluminum fixed point within the uncertainty limits of both laboratories. Furthermore, the results of this bilateral-comparison were compared with results that both laboratories achieved in the EURAMET K4 (Project 820) and were found to be in agreement.     

工业铂电阻温度计使用ITS-90温标分度方法可行性分析

国内外大多数工业铂电阻的标准(包括IEC 60751标准)均采用Callendar-Van Dusen (CVD)方程的方法来分度工业铂电阻温度计.而现行国际温标ITS-1990采用不同温区的内插公式来分度铂电阻温度计,研究表明,在CVD方程和ITS-90温标的内插公式之间存在系统差异,采用ITS-90国际温标的方法用于工业铂电阻温度计理论上是可行,但需要进一步的数据支持和实验验证,而如何有效的使用则需要更广泛和深入的研究探讨.