200 ℃以下红外温度计校准的相关研究

研制了一种可用于200 ℃以下的红外温度计校准的标准黑体辐射源。应用3种不同方法的计算,得到的黑体空腔的有效发射率均在0.997以上。通过一系列的试验,得出工作距离与环境温度是2个重要影响因素,给出了校准中的最佳工作距离,并指出保持温度计环境温度恒定的重要性。     

工业辐射温度计的辐射源尺寸效应（SSE）测量

本文给出了直接法测量工业用辐射温度计SSE的计算公式和SSE对测温结果影响的修正公式。建立直接法测量系统,对几种不同型号的被测辐射温度计的测量结果表明,SSE整体上随辐射源尺寸的增大而增加。但在源尺寸较小时SSE变化率较大,随着源尺寸的增大,SSE的变化率逐渐较小,趋于平缓。辐射温度计的校准应尽量选择与测温对象尺寸相近的辐射源直径。否则,精密测温应用需考虑SSE修正。     

测量距离影响辐射温度计检定结果的实验研究

针对测量距离对辐射温度计检定结果的影响进行了实验研究,给出了几种所选择的常用的辐射温度计的实验数据和分析图表。确定了辐射温度计的最佳测量距离是在离开黑体辐射源靶面0.3~0.5 m范围内。     

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。     

孔径光阑对辐射源尺寸效应（SSE）的影响研究

辐射源尺寸效应（SSE）是辐射测温的重要不确定度来源,本文设计了辐射温度计实验测试装置,在理论分析的基础上通过改变孔径光阑设置,研究辐射温度计SSE的变化。孔径适宜的孔径光阑在光轴任意位置都能起到限制接收立体角的作用,但实验表明设置在会聚透镜之后的SSE明显小于其他位置。本实验研究结果可为辐射温度计和绝对辐射法热力学温度测量的SSE优化设计提供参考依据。     

辐射源尺寸效应实验方案设计

在进行辐射温度计的校准时,辐射源尺寸效应会给校准结果带来影响,需设计一套实验方案,完成辐射源尺寸效应实验,以便在辐射温度计的校准中减小源尺寸效应的影响.本文重点讨论了适合本实验室的实验方案设计、实验过程及结果分析.同时对辐射温度计的校准给出了指导意见.     

工作用辐射温度计检定装置自动瞄准系统的探讨

检定工作用辐射测温仪时,应按照规程和产品说明书要求,在适当的距离上瞄准黑体源腔体的中心点,否则,会对检定准确性产生一定影响。常规手动的瞄准方法,瞄准的准确性和重复性都差。本文提出了一种工作用辐射温度计检定装置自动瞄准系统,不仅可以提高工作效率,更能降低辐射温度计的辐射源尺寸效应,提高检定准确度。     

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。     

与计量新人共享两类温度检定的技术要点

本文结合温度计量实践工作,对两类温度计量器具的测量原理、校准方法进行了描述;并对校准过程中遇到的常见问题及关键难点进行了分析总结,提出了解决方法。目的是通过本文与广大的温度计量工作者进行技术探讨,共同提高温度计量校准能力。使相关计量工作更上一个台阶。     

固定发射率工作用辐射温度计校准方法研究

讨论分析了用于校准固定发射率工作用辐射温度计的原理。在校准中,应用辐射面源是必要的,其发射率应与温度计的固定发射率一致,以保证温度量值传递的准确性,并分析了由于两个发射率的不一致而带来的温度误差,给出了在不同温度下由发射率偏离而引起的温度误差计算式。在发射率为0.95、温度为700 K的情况下,最大误差可以达到15 K。如果实际测量对象的发射率与温度计的固定发射率相同,则可以直接测量出被测对象的真实温度。     

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.     

Development of a Multiband near-to-far Infrared Radiance COmparator (MIRCO)

In recent years, there has been a growing demand to calibrate industrial blackbodies both at short wavelengths for lower temperatures and at long wavelengths for higher temperatures. User requests cover a very wide temperature range, from  −20°C to 1,500°C in the infrared bands used by thermal cameras or as defined by specific applications (especially the 1–3 μm, 3–5 μm, and 8–12 μm bands). Therefore, LNE (Laboratoire National de Métrologie et d’Essais) has developed a radiance comparator with a mirror-based optical system, an associated set of interference filter wheels, a modular holder for several infrared detectors, and a lock-in amplifier. This setup is designed to be very versatile in terms of wavelength and temperature. Targeted performances have a thermal resolution better than 0.05°C, and a known and controlled size-of-source effect (SSE). A silicon detector and a visible-to-near infrared integrating sphere were used to assess the stray light inside the housing, and supplementary baffles and stops were used to reduce it to an acceptable level. The investigation included measurement of the SSE for this comparator layout. Then, the performance in the 3–5 μm and 8–12 μm bands, using, respectively, indium antimonide (InSb) and mercury cadmium telluride (MCT) detectors, was evaluated using a water heat-pipe blackbody. This paper describes the modeling and the technical solutions implemented to optimize the optical system. Preliminary results are presented for the short-term stability, the thermal resolution between  −20°C and 960°C, and also the SSE up to 60 mm in these bands.     

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.     

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.     

Spatial Scatter Effects in the Calibration of IR Pyrometers and Imagers

Differences in the calibration conditions and the real-life applications of infrared pyrometers, radiometers, or imagers can contribute to significant measurement errors due to the presence of scattered light from the areas surrounding the reference source during the calibration process or the measured object in the field measurements. This out-of-field scatter (also known as size-of-source effect, SSE) has to be analyzed separately for each artifact to ensure applicability of the calibration results to the scene of actual measurement. This article discusses SSE characterization methods and specific requirements for calibrating single-element radiometers in the near- and mid-IR parts of the optical radiation spectrum. Two new SSE tools developed at National Institute of Standards and Technology to support routine calibration of IR pyrometers, radiometers, and imagers at the recently developed Advanced Infrared Radiometry and Imaging (AIRI) facility are described. The results of characterization of different commonly used radiometers, including an industrial-grade pyrometer, a high-accuracy pyrometer, two different infrared spectrometers, and an infrared imager, are presented.     

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.