Calibration Of Platinum Resistance Thermometers Research Articles

Assessment of Hysteresis Uncertainty in the Calibration of Platinum Resistance Thermometers

Assessment of Hysteresis Uncertainty in the Calibration of Platinum Resistance Thermometers

Temperature dependence of the zero-field splitting parameter of nitrogen-vacancy centre ensembles in diamond considering microwave and laser heating effect

The nitrogen-vacancy (NV) centre in diamond is regarded as a promising micro-nano scale thermometer due to its high stability, good temperature resolution and its scope for integration. The relation between the zero-field splitting parameter (D) and temperature (T) is fundamental for its applications. In this work, an optical system that uses continuous-wave optically detected magnetic resonance technique for the measurement of D-T was built. The temperature measured by a home-made thermostatic system and two calibrated platinum resistance thermometers was regarded as reference. Before D was measured, microwave and laser heating effect was investigated quantitatively. The drift of D at different microwave and laser power in this system was observed. Although the dips’ contrast could be improved by higher microwave power, the heating effect was significant if the power was higher than—5 dBm. The heating effect from laser power showed a linear trend which could be corrected by an average factor of −3.69 × 10−5 GHz mW−1. By using the optimized parameters, D was measured from 298 to 383 K. The reliability of our experimental method can be demonstrated by the good agreement between the present data and those obtained from similar samples. Our work provides a reference for similar experiments that the heating effect could not be neglected, which would be essential to obtain a more precise D-T relation when considering the NV centre as a thermometer. The inconsistency existing in the results from different groups indicates that further metrological investigations are still needed for the application of the NV centre as a practical and accurate thermometer in the near future.

Static characteristics calibration of Pt/Au thin-film thermocouple by means of laser heating and temperature extrapolation method

Thin-film thermocouples (TFTCs), owing to their fast response, show promise for use in temperature measurements with high spatial and temporal resolution. Because of the huge difference in the temperature profiles in the calibration and application, in the strictest sense, the standardised thermocouple calibration method is no longer suitable for TFTCs. However, this issue is always ignored in some TFTC research literature. To realise accurate calibration of a TFTC, a novel method is proposed in this article. The highlight of this method is the use of a laser to heat the hot junction of the TFTC. Then, according to the surrounding calibrated platinum resistance thermometers and the temperature distribution model, the temperature of the hot junction is calculated with an extrapolation method. Finally, the static characteristics of the TFTC are calibrated through establishing the function between the calculated temperatures and the electromotive forces (EMFs). In order to verify the applicability of this method, a Pt/Au TFTC sensor is designed on a thin cylindrical substrate. Through numerical simulation, a logarithmic model is obtained to describe the temperature distribution regularity of the sensor under laser heating. With screen-printed sensor fabrication and experimental setup realisation, the EMFs and resistances of the platinum resistors are recorded simultaneously. The results leads to the following three conclusions. First, this method can calibrate the Seebeck coefficient of the legs of the TFTC, where the temperature gradient is concentrated in applications. Second, the method shows good repeatability and stability in three repeated experiments. Third, the value of the calibrated temperature and the EMF curve of the TFTC are similar to those of bulk Pt/Au thermocouple. This signifies that the proposed calibration method is reliable and effective.

Final report on SIM.T-S5: comparison of the calibration of 100 Ω platinum resistance thermometers

An International Comparison on industrial Platinum Resistance Thermometers (PRTs) among the National Metrology Institutes (NMIs) of Spain, Panama, Honduras, El Salvador, Costa Rica and Nicaragua began in 2013 and was successfully completed in 2014. Two PRTs were circulated (hand carried) and compared in the range from -38.8 °C up to 250 °C. The Centro Español de Metrología (Spanish NMI), CEM, acted as the pilot laboratory providing the reference value of the comparison.The thermometers have shown an acceptable behavior throughout the comparison, therefore the results can be considered valid for comparing the measurement capabilities of the participant laboratories. The equivalence between the participant laboratories in the calibration of platinum resistance thermometers by comparison in the range from -38,8 °C up to 250 °C has been demonstrated in almost all cases.This report presents the results of this comparison and provides detailed information of the measurements performed by the participating laboratories.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCT, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Conclusions and some comments on the calculation of uncertainty when constructing a temperature scale

This paper is a continuation of [1], in which we considered a procedure for calculating uncertainties when constructing the International Temperature Scale of 1990 (ITS-90) using standard platinum resistance thermometers. This procedure follows directly from [2]. The present paper supplements [1] as regards problems of covariance between the resistance of a platinum resistance thermometer when measuring temperature and its resistance at fixed points. Some statements were also formulated in [3–5]. Since the international document of the BIPM [6] has already been accepted in this area, the procedure for calculating uncertainty when analyzing their individual sources is already being used. In this paper, we show that it is possible to take into account any covariance between these resistances. The use of the proposed procedure gives results that are similar to the procedure based on orthogonal interpolation functions [6–10]. General Uncertainty of the Result of a Measurement of Temperature by a Calibrated Platinum Resistance Thermometer. To calculate the temperatures T when they are measured using a platinum resistance thermometer in accordance with the ITS-90, the following inversion equation holds [11]:

Static expansion primary vacuum standard — Part 1: Determination of the volume ratio of the expansion stage

Measurement of volume ratio forms an essential part of the characterization of a static expansion system (SES) for the generation of pressures in the medium and high vacuum region. Because of the complexity of the vacuum chambers, it is not possible to determine the absolute volumes of the chambers involved. Hence an expansion process is resorted to, in which the gas enclosed in the small volume at a known pressure is allowed to expand, under isothermal conditions, into the large volume. The accuracy of the volume ratio thus determined depends on the stability of the vacuum gauges used for the measurement of initial and the final pressures and the ambient temperature. High accuracy resonant silicon gauges (RSGs) of two different ranges, one 130 kPa full scale and the other 1 kPa full scale for measurement of the initial and final pressures are found to be useful. This paper reports the results obtained with these RSGs for the measurement of the volume ratio of the National Physical Laboratory, India (NPLI) SES which is nominally 2820. With the use of the RSGs, and calibrated platinum resistance thermometers (PRTs) mounted inside the vacuum chambers, it has been possible to measure the volume ratio within the relative expanded uncertainty (k = 2) of 0.0014. The results of the volume ratio determination exercise are given in this paper while the Part 2 of this paper will discuss the procedure for the calibration of spinning rotor gauges on the Static expansion primary standard.

Uncertainty of the Calibration of Paired Temperature Sensors for Heat Meters

In heat meters, the temperatures of the incoming and the outgoing water are measured with calibrated platinum resistance thermometers. They are subject to legal metrology and the requirements for the uncertainty associated with the temperature difference are specified in national and regional standards. It is difficult to calculate this uncertainty, since it depends on the characteristics of both sensors and correlation needs to be considered. Causes of that correlation include calibration in the same facility, losses due to heat conduction, and common electrical measurements. Therefore, an analytical calculation of the temperature difference and the associated uncertainty is quite complicated, requiring several steps, corrections, and approximations. Monte Carlo techniques avoid these difficulties by simulating the calibration of both sensors simultaneously. As expected, the correlation reduces the uncertainty associated with the temperature difference indicated by the sensor pair considerably. Monte Carlo simulation and analytical calculations are briefly described and their results are compared.

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.

The NPL InSb-based Radiation Thermometer for the Medium Temperature Range ( < 962°C)

Over the temperature range from 156 to 962°C, the NPL maintains a series of heatpipe blackbody sources for the calibration of customer sources, radiation thermometers, and thermal imagers. The temperature of each of the sources is determined using a calibrated platinum resistance thermometer or gold-platinum thermocouple placed close to the radiating surface at the back of the cavity. The integrity of such a blackbody source relies on it having good temperature uniformity, a high and well-known effective emissivity, and having the sensor in good thermal contact with the cavity. To verify the performance of the blackbody sources, it is necessary to use an infrared thermometer that has been independently calibrated to compare the radiance temperature of the source with the temperature measured by the contact sensor. Such verification of the NPL blackbodies has been carried out at short wavelengths: from 500 to 1,000°C using the NPL LP2 calibrated using the NPL gold point, and at 1.6 μm using an InGaAs-based radiation thermometer calibrated at a series of fixed-points from indium (156°C) to silver (962°C). Thermal imaging systems traditionally operate over the 3–5 μm waveband and are calibrated using NPL sources. Up until now, it has not been possible to verify the performance of the sources in this waveband except indirectly by cross-comparison of the sources where they overlap in temperature. A mid-infrared (nominally 3–5 μm) radiation thermometer has, therefore, been designed, constructed, and validated at NPL. The instrument was validated and calibrated using the fixed-point blackbody sources and then used to validate the heatpipe blackbodies over their temperature range of operation. The results of the instrument validation and blackbody measurements are given.

Comparing fixed points of the ITS-90 as realized in Canada, Argentina and Brazil

A set of fixed points maintained by national metrology institutes (NMIs) for calibrating platinum resistance thermometers (PRTs) in Canada (National Research Council, NRC), Argentina (Instituto Nacional de Tecnologia Industrial, INTI) and Brazil (Instituto Nacional de Metrologia, Normalizaçãoe Qualidade Industrial, INMETRO) were compared using two methods. A set of portable cells was used in one method, and in the other a calibrated PRT. The fixed-point differences were as follows. For the INTI the differences ΔT = T(INTI) − T(NRC) found at the Ag, Al, Zn, Sn, In, Ga and Hg points were 3.5 mK, 2.8 mK, 1.8 mK, −0.5 mK, 0.2 mK, −0.2 mK and −0.5 mK, respectively. For the INMETRO the differences ΔT = T(INMETRO) − T(NRC) at the above fixed points are 0.7 mK, 3.3 mK, −1.3 mK, −1.9 mK, −0.3 mK, −0.1 mK, −0.4 mK, respectively, and 0.8 mK at the Ar point.

A High-Precision Carbon-13 Shift Thermometer for the Temperature Range 100–300 K

The first carbon-13 shift thermometer for the temperature range of 100–300 K is based on the very rapid equilibration of a pair of semibullvalene valence tautomers. The temperature dependence of the equilibrium constant is reflected in strongly temperature-dependent shift differences Δδ between averaged signals, e.g.,d(Δδ)/dT= 0.051 ppm K−1at 300, 0.087 ppm K−1at 200, and 0.175 ppm K−1at 110 K for the quaternary carbon atoms C2 and C6. At 37 temperaturesT, which were measured with calibrated platinum resistance thermometers, shift differences Δδ were taken from nondecoupled carbon-13 spectra recorded from solutions of 1 in mixtures of chlorodifluoromethane and deuterated dimethyl ether without spinning. The least-squares fit of these Δδ vsTdata to a polynomial equation of the fourth degree (Eq. [5],r2= 0.9999) allows the calculation of temperatures from measured shift differences with a standard deviation of 0.46 K and an estimated error of about 1 K. The heating effects of WALTZ-16 decoupling and the influence of solvents on Δδ are investigated. A comparison with existing NMR thermometers demonstrates the superior performance of the new carbon-13 shift thermometer with respect to precision and the accessible temperature range.

Non-uniqueness of the ITS-90 (uncertainties in temperature measurements)

Causes of uncertainties in temperature measurements are analysed. Some uncertainties are intrinsic to the temperature scale itself (built-in uncertainties). The rest are due to an assortment of experimental uncertainties. A simplified calibration procedure is proposed in the temperature range 0 °C ⩽ T ⩽ 660 °C that reduces the time (and thus the cost) of calibration by about 30% without a significant change in the accuracy of the scale imprinted on the calibrated platinum resistance thermometers.

A gold/platinum thermocouple reference table

The thermoelectric voltage of the gold/platinum thermocouple has been measured over the range 0–962 °C by comparison with calibrated platinum resistance thermometers. From 0 to 500 °C, the measurements were carried out in stirred liquid baths; from 660 to 964 °C, they were carried out in a pressure-controlled sodium-filled heat pipe furnace that provided an isothermal intercomparison environment. Measurements were also made in the metal freezing points of indium, tin, zinc, antimony, and silver, at the melting point of gallium, and at the liquidus point of the silver-copper eutectic. By fitting the measured thermoelectric voltages to a single eighth-degree polynomial in temperature by the method of least squares, a reference function is obtained for the Au/Pt thermocouple that provides emf as a function of temperature (ITS-90) to within ±10 mK from 0 to 962 °C. The Au/Pt thermocouple merits serious consideration for precise temperature measurements as its stability approaches that of the high-temperature platinum resistance thermometer.

Direct Measurement of the Discontinuity in dt/dt68 at 630.74°C in the IPTS-68

Although the IPTS-68 is meant to be a close approximation to thermodynamic temperatures, its definition makes no provision for continuity in dt/dt68 at 630.74°C. Any discontinuity in dt/dt68 at 630.74°C is directly related to the corresponding discontinuity in the first derivative with respect to t68 of sensor output, so the former can be obtained from measurement of the latter. The magnitude of the discontinuity has not previously been measured precisely; it has an important bearing on elucidating the behaviour of (t - t68) near 630.74°C. Over the temperature range from about 610°C to 645°C two calibrated platinum resistance thermometers, nine platinum - 10% rhodium/platinum thermocouples, and two other types of thermocouples have been intercompared in an experimental arrangement designed expressly to measure the discontinuity. The result for the relative discontinuity in dt/dt68 at 630.74°C was found to be 0.51 ± 0.10 percent.

A cryogenic temperature controller with a stability of ±0.03K over several days

Describes the construction and operation of a temperature controller which has been used in the range of 85-105K. A stability of +or-0.03K in space and time can be ensured for a continuous operation stretching over several days. Calibrated platinum resistance thermometers have been used along with suitable bridges for measurement and control. A continuous controlled gaseous nitrogen flow and a nichrome-wire base heater ensure the stability mentioned above. A thermal discriminator has been developed which controls the threshold and hysteresis settings of the controller. A schematic diagram of the control system and the electronic circuitry used for the thermal discriminator are given. A salient feature is that no vacuum is used in the set-up. This controller has been successfully used with an apparatus for the determination of diffusion coefficients of krypton in liquid argon.

A simple engineering calibration for platinum resistance thermometers in the temperature range 4.2 K - 273 K

We describe how a simple two-point calibration of a platinum resistance thermometer can be used to deduce the resistance-temperature relationship in the range 4.2 K ⩽ T ⩽ 273 K. This relationship is established by comparing the unknown thermometer to two carefully calibrated platinum resistance thermometers. This technique produces an accuracy of (0.1 – 0.3) K. This accuracy should be adequate for many engineering applications.

Precision measurements of the thermal conductivity, electrical resistivity, and Seebeck coefficient from 80 to 400 K and their application to pure molybdenum

A longitudinal heat-flow technique for precise measurement of thermal conductivity, electrical resistivity, and Seebeck coefficient over the temperature range from 80 to 400 K is described. The basis of the technique is the use of a calibrated platinum resistance thermometer to provide in situ calibrations of specimen thermocouples. The total determinate errors at 273 K are ± 0.23% for electrical resistivity, ± 0.49% for thermal conductivity, and ± 0.07 μV/K for the Seebeck coefficient when Pt wire is used as the reference. Experimental results on two high-purity molybdenum specimens with cross-sectional areas differing by a factor of four are presented to demonstrate the system precision and low level of indeterminate erros.

Thermal Expansion of Copper from 20 to 800 K—Standard Reference Material 736

Copper is the first of a series of materials that will be certified as thermal-expansion standards by the National Bureau of Standards. The results of tests on five specimens indicate the stock is of consistent quality so that it may be certified as Standard Reference Material 736. A Fizeau interferometer was used for the expansion measurements. Above room temperature a controlled-atmosphere furnace using a calibrated Pt vs Pt-10% Rh thermocouple was used. Below room temperature a cryostat capable of operation with both liquid nitrogen and helium was used with a calibrated platinum resistance thermometer. Values of expansivity were calculated between equilibrium temperatures. The expansivity was used in the analysis of the data. Third-order polynomials were fitted to the data for each of the five specimens in the overlapping temperature ranges from 0 to 70 K, 50 to 270 K, and 210 to 800 K to test for variations between the specimens. The deviations between the five equations were well within the standard deviations of the data for each of the specimens in the respective temperature intervals. All the expansivity data were then pooled and used to obtain an equation for each of the temperature ranges given above. These equations and their integrals were used to calculate the final values of expansivity and expansion, respectively. The results of the statistical analysis of the expansion and expansivity data are presented. A comparison is made with the data in the literature.

Calibration of platinum resistance thermometers at two points

Calibration of platinum resistance thermometers at two points