Development of a New InGaAs Radiation Thermometer at NMIJ

The first InGaAs radiation thermometer at NMIJ was developed more than ten years ago as a standard radiation thermometer operating from 150 to 1,100°C. Its size-of-source effect (SSE) was as large as 1% from 6 mm in diameter to 50 mm in diameter. The new thermometer has an SSE of 0.3%. The reason for the error in measuring the SSE of InGaAs thermometers was also found. The new thermometer at first suffered from nonlinearity and the distance effect (DE). These deficiencies arose from the misalignment of optics inside the thermometer and were solved by increasing the detector size from 1 mm in diameter to 2 mm in diameter. Unfortunately, the detector of 2 mm diameter had a smaller S/N ratio than that of the 1 mm one at the indium (In) point. The final design uses a detector of 1 mm diameter, but the radiation is focussed on a smaller area of the detector. The new thermometer is smaller and lighter than preceding designs and other standard InGaAs radiation thermometers. The temperature of the main part of the instrument, including the filter, the detector, and the preamplifier board, is controlled at 30°C. In addition to the calibration with the six fixed points of copper (Cu), silver (Ag), aluminum (Al), zinc (Zn), tin (Sn), and indium (In), the linearity from the In point to the Cu point, the SSE, the DE, and the spectral responsivity were measured.     

Calibration of an Absolute Radiation Thermometer for Accurate Determination of Fixed-Point Temperatures

For accurate determinations of thermodynamic temperature, NPL has developed its absolute radiation thermometer (ART), which is calibrated traceably against a cryogenic radiometer. This article reviews some of the potential sources of systematic uncertainty present in the calibration and use of ART. In particular, this article is concerned with the evaluation of the size-of-source effect and the lens transmittance, as well as potential differences in the responsivity of a transfer trap detector when calibrated in terms of radiant power and used in irradiance mode.     

Optical Diffraction Corrections in Radiometric Thermodynamic Temperature Determination

One of the main components of uncertainty in high-temperature thermometry arises because of the size-of-source effect (SSE). This effect makes the temperature measurement sensitive to the geometry of the radiating environment. It is caused by optical diffraction and especially by light scattering off/from, and inter-reflections between, optical components inside the pyrometer. The LNE-INM/CNAM is involved in extending the thermometry temperature scale to very high temperatures (T > 2000 °C) and has developed eutectic-based fixed points (Sadli et al. (in: Zvizdic (ed.) Proceedings of TEMPMEKO 2004, 9th International Symposium on Temperature and Thermal Measurements in Industry and Science, 2004)) and a thermodynamic temperature measurement capability based on absolute radiometric methods (Briaudeau et al. (in: D. Zvizdic (ed.) Proceedings of TEMPMEKO 2004, 9th International Symposium on Temperature and Thermal Measurements in Industry and Science 2004)). A new measurement technique that uses an optical fiber has been developed and tested, allowing the determination of the SSE at any defocusing plane, with high resolution. A model based on optical diffraction has been developed to simulate the SSE in a real situation, considering the contribution to the pyrometer signal of the whole “3D” optical scene inside the blackbody furnace. Using the same approach, it has been demonstrated that optical scattering in a simple radiance meter can be estimated from accurate optical diffraction measurement.     

Acoustic Thermometry Results from 271 to 552 K

The NIST acoustic thermometer determines the thermodynamic temperature from measurements of ratios of the speed of sound of argon in a nearly spherical cavity. We report recent results for T − T ₉₀ on 12 isotherms spanning the range 271–552 K. (T is the thermodynamic temperature and T ₉₀ is the temperature on the International Temperature Scale of 1990.) The results are in excellent agreement with recent acoustic thermometry results reported by Benedetto et al. in the range from 273 to 380 K and with our previously reported results at 303, 430, and 505 K. The combined data sets are sufficiently redundant and sufficiently distributed over the temperature range to support a re-determination of the reference function for standard platinum resistance thermometers for a future temperature scale. The isotherms were analyzed using several methods; the T−T ₉₀ results and related uncertainties are insensitive to the method chosen. The thermal expansion of the stainless-steel resonator was deduced from the frequencies of the microwave resonances of the cavity. To clearly identify two nearly degenerate eigenmodes in our nearly axially symmetric resonator, two phased coupling probes were used to control the azimuthal angle of the microwave excitation.     

环境温度对红外辐射式体温计读数的影响

本简要介绍了所研制的红外辐射式体温计的构成及标定实验方法；研究了环境温度对体温计的影响；并在实验基础上提出了采用分段标定及对环境温度补结果进行修正的方法，提出了测量精度。     

NMIJ Constant-Volume Gas Thermometer for Realization of the ITS-90 and Thermodynamic Temperature Measurement

The constant-volume gas thermometer (CVGT) of the National Metrology Institute of Japan (NMIJ), AIST with ³He as the working gas is used as an interpolating gas thermometer to realize the International Temperature Scale of 1990 (ITS-90) from 3 K to 24.5561 K and as a relative gas thermometer for thermodynamic temperature measurement calibrated at the triple point (TP) of Ne. The standard uncertainties of the realization and measurement are estimated to be 0.58 mK and 0.86 mK at a maximum in the mentioned temperature range, respectively. The maximum difference between both temperatures is about 1 mK. In the calibration of the CVGT, the TP of equilibrium hydrogen (e-H₂) is corrected for isotopic composition as specified in the Technical Annex for the ITS-90. The ambiguity of the TP of Ne due to the variability in isotopic composition is included in the uncertainty. Although the CVGT was also used in 2004 to realize the ITS-90, it was modified for the present experiment to reduce some measurement uncertainty components and the working gas was replaced with a higher-isotopic-purity gas. The results from 2004 were recalculated by correcting for the isotopic composition of e-H₂ and differ insignificantly from the present results, except for a wider scatter.     

The VNIIFTRI magnetic temperature scale in the 0.3–3 K range

A thermodynamic temperature scale in the range 0.3–3 K is established by a magnetic method. The results of investigations enable the range of the State Standard of temperature to be extended from 0.8 K to 0.3 K with a simultaneous increase in its accuracy by a factor of 2–3. __________ Translated from Izmeritel’naya Tekhnika, No. 8, pp. 47–53, August, 2007.     

The Influence of Distance and Focus on the Calibration of Infrared Radiation Thermometers

If a radiation thermometer is calibrated by measuring the temperatures of two cavities having different geometries, sometimes discrepancies arise between them, even though their emissivities are close to that of a blackbody. The origin of such discrepancies may result from the size-of-source effect, and in the distance-to-target effect for those thermometers that offer focusing capability. Examples include: (a) out-of-focus image changes the reading: different focus settings produce different results and (b) measurements taken at different distances produce different results. These effects are discussed, their contribution to the measurement uncertainty is evaluated, and some recommendations are made for practical blackbody cavities or radiators to reduce such effects.     

Calculated Uncertainty of Temperature Due to the Size-of-Source Effect in Commercial Radiation Thermometers

The article evaluates the uncertainty in the temperature indicated by a radiation thermometer with a direct readout in temperature, due to the uncertainty in measuring the size-of-source effect (SSE) by the so-called “direct method.” Radiation thermometers of this type are the ones most frequently used in practice. The uncertainty of the SSE characteristic is usually not a useful quantity to report to users of commercial radiation thermometers. Instead, they would prefer to know the uncertainty in the measured temperature that results from the uncertainty of the SSE characteristic, and this will be the result of our analysis. The user of a direct reading radiation thermometer will be able to take into account the uncertainty of temperature due to the SSE, if a target with known dimensions is measured. The uncertainty in temperature due to the SSE of analyses based on Planck’s law and its approximation, Wien’s law is compared.     

Middle Temperature Scale for Infrared Radiation Thermometer Calibrated Against Multiple Fixed Points

The NMIJ has established a temperature scale for infrared radiation thermometry from 100 to 420°C consisting of three fixed-point blackbodies at the In, Sn, and Zn points and an InSb detector thermometer at a wavelength of 4.7 μm. The blackbody cavities have large openings of 15 mm diameter. The expanded uncertainties (k = 2) of the In, Sn, and Zn fixed-point radiance temperatures are estimated to be 0.03, 0.03, and 0.05 K, respectively. The expanded uncertainties (k =  2) for the calibration of the infrared radiation thermometer are estimated to be 0.04 K at 157°C (In point), 0.04 K at 232°C (Sn point), and 0.07 K at 420°C (Zn point).     

红外辐射温度计的辐射源尺寸效应修正

红外辐射温度计在低温测量的辐射源尺寸效应（SSE） 的规律不同于高温测量。基于以虚拟探测器温度消除背景辐射影响的SSE计算模型,推导了在不同源尺寸和不同背景条件下辐射温度计输出的SSE影响修正公式;得出不同源尺寸条件下辐射温度计温度示值的SSE影响修正的理论解析表达式。在源温度低于或接近背景温度时修正模型与高温测量SSE修正模型有显著差异。所得结果适用于任意温度下对单波段辐射温度计的SSE影响修正。     

标准铂电阻温度计自热效应对测量结果的影响

为了研究自热效应对标准铂电阻温度计测量结果的影响,分别从定点法和比较法两方面开展研究.针对定点法,统计中国计量科学研究院近3年检定的标准铂电阻温度计数据,计算不同温区的铂电阻温度计自热效应修正前后的测量结果并进行对比,结果表明,在溯源标准铂电阻温度计时自热效应修正与否对测量结果的影响达到了1.5 mK以上,最大达到了6...     

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.     

New PTB Setup for the Absolute Calibration of the Spectral Responsivity of Radiation Thermometers

The paper describes the new experimental setup assembled at the PTB for the absolute spectral responsivity measurement of radiation thermometers. The concept of this setup is to measure the relative spectral responsivity of the radiation thermometer using the conventional monochromator-based spectral comparator facility also used for the calibration of filter radiometers. The absolute spectral responsivity is subsequently measured at one wavelength, supplied by the radiation of a diode laser, using the new setup. The radiation of the diode laser is guided with an optical fiber into an integrating sphere source that is equipped with an aperture of absolutely known area. The spectral radiance of this integrating sphere source is determined via the spectral irradiance measured by a trap detector with an absolutely calibrated spectral responsivity traceable to the primary detector standard of the PTB, the cryogenic radiometer. First results of the spectral responsivity calibration of the radiation thermometer LP3 are presented, and a provisional uncertainty budget of the absolute spectral responsivity is given.     

Approximating the ITS-90 between Zinc and Copper with an Infrared Thermometer at NIS-Egypt

This paper presents an approximation to the International Temperature Scale of 1990 (ITS-90) between the Zn (420 °C) and Cu (1085 °C) fixed points using a 900 nm narrow-band radiation thermometer. This thermometer has a 400 mm working distance and a 150 mm objective focal length. An image of the measured target is focused by the objective lens onto a 1 mm aperture (drilled mirror). The light passing through the aperture is conveyed by a condenser lens through an interference filter with a nominal central wavelength of 900 nm and a half-bandwidth of 10 nm before reaching a silicon photodiode working in the photovoltaic mode. The thermometer was calibrated at the Zn, Al, Ag, and Cu blackbody fixed points. The results of the calibration were used to determine the constants A, B, and C of the Sakuma-Hattori interpolation equation. The results showed that the ITS-90 can be approximated within ± 0.051 °C throughout the Zn-Cu interval when the thermometer is calibrated at the Zn, Al, Ag, and Cu fixed points.     

红外辐射温度计瞄准的平面辐射源模型

用典型红外辐射温度计的辐射源尺寸效应的实验数据说明不同测量条件下的检定/校准结果的差异可能为其最大允许误差绝对值的数倍。提出具有明确测量条件的平面辐射源瞄准模型和以辐射源前置光阑的方式对于不同空腔黑体辐射源实现相同的等效平面源直径的方法,提出了对光阑的技术特性和放置距离要求,分析表明低温辐射源对光阑的冷却作用可能引起不可忽略的示值降低。采用等效平面源模型的实验结果表明以不同几何条件的空腔黑体辐射源可得到一致的检定结果。讨论了应用平面辐射源模型可能遇到的实际技术问题和解决的对策。     

AC-Mode Short-Wavelength IR Radiation Thermometers for Measurement of Ambient Temperatures

Recent improvements in the fabrication of short-wave infrared (SW-IR) quantum detectors have opened a new era in radiation thermometry. Ambient and higher temperatures can be measured with low uncertainties using thermoelectrically (TE) cooled extended-InGaAs (E-IGA) and short-wave photovoltaic-HgCdTe (SW-MCT) detectors. Since these detectors have low cut-off wavelengths (2.5 μm and 2.8 μm, respectively), they do not respond past cut-off and are less sensitive to the background infrared radiation, resulting in orders of magnitude lower background noise than traditional broad-band infrared detectors such as cryogenically cooled quantum detectors or thermal detectors. At the same time, the cut-off is far enough in the infrared to obtain a large enough signal from the source of interest. Because of the low detector cut-off wavelength, traditional glass-based optics can be used in the radiation thermometers. A chopper-produced alternating-current (AC) signal was used to measure low temperatures by separating the AC signal from the background-radiation-produced direct-current (DC) signal and its fluctuations. Design considerations and characteristics of a newly developed SW-IR radiation thermometer are discussed. A noise-equivalent temperature difference (NETD) of < 3mK for a 50°C blackbody was measured. At the human body temperature of 36°C, the obtained NETD of ~10mK indicates that these detectors can be used in non-contact temperature measurements to replace thermopile- or pyroelectric-based radiation thermometers.     

较低温度条件下SSE影响红外温度计校准的实验研究

讨论了光源尺寸效应（SSE）现象,并应用SSE系数对红外温度计的SSE特性进行估计。介绍了用于较低温度条件下测量SSE的实验装置,应用该装置对几种红外温度计进行了测试。测试结果表明,当黑体辐射源的光阑孔径大于40 mm时,可以不考虑SSE的影响。该结论适用于大多数工业用温度计的校准。     

A Summary of Lightpipe Radiation Thermometry Research at NIST

During the last 10 years, research in light-pipe radiation thermometry has significantly reduced the uncertainties for temperature measurements in semiconductor processing. The National Institute of Standards and Technology (NIST) has improved the calibration of lightpipe radiation thermometers (LPRTs), the characterization procedures for LPRTs, the in situ calibration of LPRTs using thin-film thermocouple (TFTC) test wafers, and the application of model-based corrections to improve LPRT spectral radiance temperatures. Collaboration with industry on implementing techniques and ideas established at NIST has led to improvements in temperature measurements in semiconductor processing. LPRTs have been successfully calibrated at NIST for rapid thermal processing (RTP) applications using a sodium heat-pipe blackbody between 700 °C and 900 °C with an uncertainty of about 0.3 °C (k = 1) traceable to the International Temperature Scale of 1990. Employing appropriate effective emissivity models, LPRTs have been used to determine the wafer temperature in the NIST RTP Test Bed with an uncertainty of 3.5 °C. Using a TFTC wafer for calibration, the LPRT can measure the wafer temperature in the NIST RTP Test Bed with an uncertainty of 2.3 °C. Collaborations with industry in characterizing and calibrating LPRTs will be summarized, and future directions for LPRT research will be discussed.     

Thermometer for between 0.01 and 4 K using a carbon resistor

We present an original mounting for a carbon resistor. This device, when used as a thermometer, has displayed very good cooling ability and excellent reproducibility down to 10 mK.