Calibration of Contact Surface Thermometers

Some of the national metrology institutes (NMIs) have developed devices which generate a standard surface temperature under conditions which resemble, as closely as possible, those encountered during the routine use of surface sensors. Several comparisons of measurements among European NMIs, coordinated by MKEH, were undertaken in order to validate the methods used and the reference conditions. The characteristics of the reference surface significantly influence the measurement error, as its temperature, inclination and thermophysical properties. This paper presents a method of determining a correction function, containing the effects of these factors. The measurements have been taken in the temperature range from \(100\,^{\circ }\hbox {C}\) to \(500\,^{\circ }\hbox {C}\), with a specific sensor having an inflexible head. The technique developed of MKEH is suitable for quantifying the effect of the above parameters, optimizing the surface temperature measurements in this regard.     

浅谈红外测温仪在线温度校准

本文讲述在线红外测温仪测量温度的准确与否将直接影响烟丝的内在质量,为了保证烟丝的工艺质量必须对红外测温仪进行现场校准。     

Melting Temperatures of Eutectic Fixed-Point Cells Usable for the Calibration of Contact Thermometers

The objective of the present investigation was the determination of the melting temperatures of the eutectic compounds Fe–C, Co–C, and Ni–C. Six eutectic fixed-point cells of the Physikalisch-Technische Bundesanstalt (PTB) (Fe–C1, Fe–C2, Co–C1, Co–C2, Ni–C1, and Ni–C2) and two cells of the Brazilian National Metrological Institute (Inmetro) (Fe–C1V and Ni–C1V), useable for the calibration of contact thermometers, were investigated. Their melting temperatures were calculated by extrapolation of the emf-temperature characteristics of four stable Pt/Pd thermocouples, which were calibrated at the eutectic fixed points and at conventional fixed points of the International Temperature Scale of 1990 (ITS-90). On the basis of the eight eutectic fixed-point cells and seven independent calibration runs, the melting temperatures of the Fe–C, Co–C, and Ni–C eutectics resulted in 1153.67 ± 0.15°C, 1323.81 ± 0.27°C, and 1328.48 ± 0.20°C, respectively, with expanded uncertainties corresponding to a coverage factor of k = 2.     

A CFD Study on a Calibration System for Contact Temperature Probes

Surface-temperature measurements by means of contact probes require a detailed investigation of the probe-surface interaction. For an accurate calibration of such probes, the heat transfer processes involved in contact measurements must be well known and the impact of any influence parameters must be taken into account. At present, contact probes are generally calibrated by means of a temperature-controlled hot plate. A calibration system for contact surface-temperature probes, based on such a hot plate, was developed at INRIM. It covers the temperature range from ambient to 350 °C. The reference temperature is available on the upper surface of a metal block and is determined by linear extrapolation of the readings of three calibrated thermometers embedded into the block at different depths. However, the actual temperature of the reference surface largely depends on the sensor-to-surface interaction. The contact thermal resistance, the thermal conductivity of the block, the geometry of the probe, and the temperature of the surrounding fluid are just some of the parameters that affect a calibration and that may cause measurement errors if they are not properly taken into account and corrected for. Better insight into the interaction between the surface and the probe is therefore required. Since the experimental evaluation of measurement errors is not straightforward, mathematical modeling could represent a crucial tool to better understand the interactions between the probe and the calibration system. In this paper, a finite-element numerical model of the INRIM calibration system was developed in order to investigate the temperature field across the reference block as well as on its surface during a calibration. The thermal load introduced by a commercial contact probe during a calibration was also included in the simulation and its effect on the temperature field was studied. In order to obtain a detailed mathematical model, the surrounding air was also included in the simulation, avoiding the imposition of boundary conditions at the interface between solid parts and fluid. The proposed model was validated by comparing the results obtained with the available experimental data.     

Development of a 300 L Calibration Bath for Oceanographic Thermometers

The Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has been developing a 300 L calibration bath to calibrate 24 oceanographic thermometers (OT) simultaneously and thereby reduce the calibration work load necessary to service more than 180 OT every year. This study investigated characteristics of the developed 300 L calibration bath using a SBE 3plus thermometer produced by an OT manufacturer. We also used 11 thermistor thermometers that were calibrated to be traceable to the international temperature scale of 1990 (ITS-90) within 1 mK of standard uncertainty through collaboration of JAMSTEC and NMIJ/AIST. Results show that the time stability of temperature of the developed bath was within \(\pm 1 \,\hbox {mK}\). Furthermore, the temperature uniformity was \(\pm 1.3 \,\hbox {mK}\). The expanded uncertainty (\(k=2\)) components for the characteristics of the developed 300 L calibration bath were estimated as 2.9 mK, which is much less than the value of 10 mK: the required specification for uncertainty of calibration for the OT. These results demonstrated the utility of this 300 L calibration bath as a device for use with a new calibration system.     

Triple-Fixed-Point Blackbody for the Calibration of Radiation Thermometers

A new triple-fixed-point blackbody containing the fixed-point materials aluminum (freezing point 660.323°C), zinc (FP 419.527°C), and tin (FP 231.928°C) in one device has been developed at the Ilmenau University of Technology. It enables calibration of a radiation thermometer with direct reference to the ITS-90 at three fixed points after a single adjustment of the calibration object. The setup significantly reduces the technical effort and the time for the calibration procedure. Measurements of the phase-transition temperature and the time-dependent blackbody temperature made with a transfer radiation thermometer, the Linearpyrometer LP5 of the IKE Stuttgart, are presented in the article.     

The Development of a Device for In Situ Calibration of Thermometers

Prototype comparator devices have been designed and constructed for the calibration of thermometers on-site and in situ. The uncertainties that can be obtained using this device can be compared with those of block calibrators. The system has reduced stem conduction losses by limiting gradients and consequent heat flows. Presently, the range of the prototype applications is limited to between ?90???C and +150???C. The article shows details on the construction, discusses evaluation tests and calibration results, and gives example uncertainty budgets.     

基于LabVIEW实现固定发射率辐射温度计校准的温度修正

在辐射温度计检定中,根据规程要求,需要将辐射温度计的发射率设置为1,而在实际校准辐射温度计的过程中发现大量发射率固定且不为1的情况,同样有用户要求校准后给出不同发射率下的辐射温度计修正值,为实现宽波段任意固定发射率辐射温度计在校准过程中的修正值计算,文章使用LabVIEW的两分法迭代实现Plank公式的积分算法,有效提高校准过程的自动化程度,文章用实例说明了两分法与普通步进算法的效率区别,从而高效的实现了任意波段、任意发射率、任意温度点的温度修正值计算。     

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.     

倾点仪的校准方法及其不确定度评定研究

本文主要介绍了一种可行的石油产品倾点试验仪的具体校准方法,并对其校准的主要参量——倾点温度示值误差进行了合理的不确定度评定,该研究为目前尚无国家校准规范的倾点仪提供了可供参考的校准方法,为计量及仪器使用人员对倾点仪的校准或性能确认提供了参考。     

关于机械式冰箱专用温度计校准的探讨

本文对不可用液体介质进行校准的机械式冰箱专用温度计的校准方法进行了探讨,并对测得值的不确定度进行了简要分析,希望对开展此类冰箱专用温度计的校准工作有所帮助.     

Calibration of Air Thermometers in a Climatic Chamber and Liquid Baths

The paper deals with calibration of digital indication thermometers designed for air temperature measurements. These were calibrated by comparison with a reference thermometer in two different calibration media: in the air when a climatic chamber was used and in a liquid when a calibration bath was used. The main difference between the media was thermal conductivity, which was more than ten times lower in the air. To compare both methods, we calibrated two sets of air thermometers twice. The first set comprised of small temperature loggers with an internal sensor, whereas the second set was a group of temperature probes connected to the measurement unit. The temperature ranges for the loggers were from 0 \(^{\circ }\)C to 40 \(^{\circ }\)C and for the probes from ?20 \(^{\circ }\)C to 60 \(^{\circ }\)C. The results showed that the measured temperature errors were smaller in the bath as well as less scattered. Furthermore, the assigned measurement uncertainty was lower, if calibration was performed in a calibration bath, mostly due to better thermal homogeneity of a liquid compared to the air in a climatic chamber. Calibration shall assure traceability of a measurement equipment in such a way that a calibration procedure simulates an actual use of equipment; otherwise, the corrections and associated measurement uncertainty could be misleading. Therefore, when air thermometers, which are designed to measure a gaseous medium, are calibrated, they should be calibrated under similar conditions as they are used. The paper presents the differences in results of calibration of air thermometers under different calibration conditions.     

Interlaboratory Comparison of Reference Surface Temperature Apparatus at NMIs

During 2001 and 2002, the first international comparison of surface temperature measurements at national metrology institutes (NMIs) was organized under EUROMET Project No 635. The coordinator for this project was the National Office of Measures (OMH) in Hungary. Among the participants were the Swedish National Testing and Research Institute (SP) from Sweden, the Centre for Metrology and Accreditation (MIKES) in Finland, and Justervesenet (JV) in Norway. The comparison showed a need for better apparatus to reduce the differences in the results from the different laboratories. As a result, a new apparatus was designed at SP and MIKES made some changes to their apparatus. To test the new and modified apparatus, SP took the initiative to arrange and coordinate a new comparison. In this recent comparison, measurements were made at temperatures from 50 to 300°C on surfaces of aluminum and stainless steel. The comparison was arranged and performed during 2005 and 2006. Participants in the comparison were OMH, MIKES, RISOE, JV, and SP. The comparison results using the newly developed apparatus show improved agreement with the earlier EUROMET intercomparison, but also indicate a need for a more standardized calibration method and apparatus to be able to perform calibrations in different laboratories with good agreement.     

Uncertainty Budgets for Calibration of Radiation Thermometers below the Silver Point

Below the freezing point of silver, radiation thermometers are generally calibrated by implementing the multi-point interpolation method using blackbody measurements at three or more calibration points, rather than the ITS-90 extrapolation technique. The interpolation method eliminates the need to measure the spectral responsivity and provides greater accuracy at the longer wavelengths required below the silver point. This article identifies all the sources of uncertainty associated with the interpolation method, in particular, those related to the reference blackbody temperatures (either variable-temperature or fixed-point blackbodies) and to the measured thermometer signals at these points. Estimates are given of the ‘normal’ and ‘best’ uncertainties currently achievable. A model of the thermometer response is used to propagate all the uncertainties at the reference points and provide a total uncertainty at any temperature within the calibration range. The multi-point method has the effect of constraining the total uncertainty over this range, unlike the ITS-90 technique for which the uncertainties propagate as T ². This article is a joint effort of the working group on radiation thermometry of the Consultative Committee for Thermometry (CCT), summarizing the knowledge and experience of all experts in this field.     

Realization of the 3He Vapor-Pressure Temperature Scale and Development of a Liquid-He-Free Calibration Apparatus

The ³He vapor-pressure temperature scale was realized using an apparatus based on a continuously operating ³He cryostat at the National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST). The cryostat has two operational modes: a ³He circulation mode and a 1 K pot mode. The ³He circulation mode can be used for ³He vapor-pressure measurements below 1.6 K, and the 1 K pot mode can be used for measurements above 1.3 K. Either mode can be selected for measurements from 1.3 K to 1.6 K. The realization of the ³He vapor-pressure temperature scale in this study fully covers its defined temperature range from 0.65 K to 3.2 K in the International Temperature Scale of 1990. The latest realization results are presented in this article. In addition, a liquid-He-free calibration apparatus was developed. It does not require liquid helium as a cryogen, which usually entails cumbersome handling and periodic refilling. The apparatus was designed for the calibration of capsule-type resistance thermometers from 0.65 K to 24.5561 K (the triple point of neon). The cooling system of the apparatus consists of a commercially available pulse-tube refrigerator and a ³He Joule?CThomson (JT) cooling circuit developed at NMIJ/AIST. The pulse-tube refrigerator is used in a pre-cooling stage and cools the apparatus to approximately 5 K. The ³He JT cooling circuit is used to cool the apparatus from 5 K to below 0.65 K. Since the ³He JT cooling circuit is a closed circuit, the apparatus can run continuously with only simple maintenance required. The basic characteristics of the apparatus are described.     

Performance of Different Light Sources for the Absolute Calibration of Radiation Thermometers

The evolving mise en pratique for the definition of the kelvin (MeP-K) [1, 2] will, in its forthcoming edition, encourage the realization and dissemination of the thermodynamic temperature either directly (primary thermometry) or indirectly (relative primary thermometry) via fixed points with assigned reference thermodynamic temperatures. In the last years, the Centro Español de Metrología (CEM), in collaboration with the Instituto de Óptica of Consejo Superior de Investigaciones Científicas (IO-CSIC), has developed several setups for absolute calibration of standard radiation thermometers using the radiance method to allow CEM the direct dissemination of the thermodynamic temperature and the assignment of the thermodynamic temperatures to several fixed points. Different calibration facilities based on a monochromator and/or a laser and an integrating sphere have been developed to calibrate CEM’s standard radiation thermometers (KE-LP2 and KE-LP4) and filter radiometer (FIRA2). This system is based on the one described in [3] placed in IO-CSIC. Different light sources have been tried and tested for measuring absolute spectral radiance responsivity: a Xe-Hg 500 W lamp, a supercontinuum laser NKT SuperK-EXR20 and a diode laser emitting at 6473 nm with a typical maximum power of 120 mW. Their advantages and disadvantages have been studied such as sensitivity to interferences generated by the laser inside the filter, flux stability generated by the radiant sources and so forth. This paper describes the setups used, the uncertainty budgets and the results obtained for the absolute temperatures of Cu, Co-C, Pt-C and Re-C fixed points, measured with the three thermometers with central wavelengths around 650 nm.     

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.     

粗糙表面轮廓的非高斯AR模型双谱估计

介绍了双谱估计的参数模型法，由AR（Auto Regression)模型参数估计粗糙工程表面的非高斯轮廓的双谱，通过对几种典型加工表面，分别采用经典双谱估计和参数模型法双谱估计后认为，即使在测量数据较少的情况下，参数化模型法仍能提供高分辨率的双谱估计精度和有效的相位信息，能较好地反映粗糙表面轮廓高度的偏斜分布程度。