H500型红外遥感定标高精度真空黑体辐射源的研制

对中国计量科学研究院研制的温度范围覆盖-93~220℃的H500型红外遥感定标高精度真空黑体辐射源进行了介绍。采用圆柱圆锥黑体腔和双层4段PID控温,在真空低背景(液氮冷却)环境下对该黑体进行了性能测试,在大气室温环境下,利用控制环境辐射反射比发射率测量方法测量了黑体空腔发射率和利用红外标准辐射温度计测量空腔底部温度均匀性等指标。实验结果表明,该黑体辐射源升温速率为1℃/min下,控制到温度点的稳定时间优于50 min,并且10 min内的温度稳定性在0.01℃以内;黑体温度设置在20℃、30℃和50℃下空腔发射率的测量结果分别为0.9965、0.9966和0.9963;其黑体底部温度均匀性优于0.03℃;在整个温度区域内扩展不确定度优于0.1℃(k=2)。     

A High-Emissivity Blackbody with Large Aperture for Radiometric Calibration at Low-Temperature

A newly designed high-emissivity cylindrical blackbody source with a large diameter aperture (54 mm), an internal triangular-grooved surface, and concentric grooves on the bottom surface was immersed in a temperature-controlled, stirred-liquid bath. The stirred-liquid bath can be stabilized to better than 0.05°C at temperatures between 30 °C and 70 °C, with traceability to the ITS-90 through a platinum resistance thermometer (PRT) calibrated at the fixed points of indium, gallium, and the water triple point. The temperature uniformity of the blackbody from the bottom to the front of the cavity is better than 0.05 % of the operating temperature (in °C). The heat loss of the cavity is less than 0.03 % of the operating temperature as determined with a radiation thermometer by removing an insulating lid without the gas purge operating. Optical ray tracing with a Monte Carlo method (STEEP 3) indicated that the effective emissivity of this blackbody cavity is very close to unity. The size-of-source effect (SSE) of the radiation thermometer and the effective emissivity of the blackbody were considered in evaluating the uncertainty of the blackbody. The blackbody uncertainty budget and performance are described in this paper.     

Construction and Characterization of a Large Aperture Blackbody for Infrared Radiometer Calibration

A large aperture blackbody (LABB) with a diameter of 1 m has been successfully constructed for calibrating radiation thermometers and infrared radiometers with a wide field of view in the temperature range between 10 °C and 90 °C. The blackbody is a 1 m long cylindro-conical cavity with a diameter of 1.1 m. Its conical bottom has an apex angle of 120°. To achieve good temperature stability and uniformity, the cavity is integrated to a water-bath to which the pressurized water is supplied from a reservoir. To reduce the convection heat loss from the cavity to the ambient, the cavity is purged of the dried air that passes through a coiled tube immersed in the reservoir. For an uncertainty evaluation of the LABB, its temperature stability was measured by using a reference radiation thermometer (RRT) and a platinum resistance thermometer (PRT), and its radiance temperature distributions on the aperture plane were measured by using a thermal camera. Measuring the spectral emissivity of the coating material, the effective emissivity of the blackbody was calculated to be 0.9955 from 1 ??m to 15 ??m. The expanded uncertainty of the radiance temperature scale was evaluated based on the PRT readings, which vary from 0.3 °C to 0.5 °C (k = 2) in the temperature range. The temperature scale is validated by comparing with the RRT of which the temperature scale is realized by a multiple fixed-point calibration.     

100～400K真空红外亮温标准黑体辐射源研制

介绍了中国计量科学研究院研制的100~400K真空红外亮温标准黑体辐射源的工作原理、结构、性能测试方法及测试结果。黑体辐射源通过液氮制冷与3温区控制实现了100~400K范围内的温度控制。在真空环境下,测试了其在温度范围100~400K轴向温度均匀性、底部温度稳定性等技术指标,结果表明均匀性优于0.120K,控温稳定性优于0.020K/20min;在室温大气环境下,利用基于控制环境辐射的发射率测量方法测量了黑体空腔发射率,空腔法向发射率为0.9998。采用基于蒙特卡罗黑体发射率仿真计算方法分析轴向温度均匀性对空腔发射率的影响,分析了标准黑体辐射源的不确定度来源,在8~16 μm波长亮度温度的合成标准不确定度优于0.030K。     

Thermodynamic Temperature Measurements Traceable to Photometric Standards

The replacement of ITS-90 temperature measurements by direct thermodynamic temperature measurements based on radiometric techniques in the temperature range above 1000 °C has been proposed by many national measurement laboratories. This article reports on work at NMIA to develop a simple and robust traceability scheme for thermodynamic temperature, based on the use of photometers and a Thermogage furnace with a graphite tube element modified to improve its temperature uniformity and emissivity. A simple luminance meter was constructed using a commercial photometer and pairs of precision apertures to view the rear of the blackbody cavity. This photometer was calibrated against NMIA reference illuminance lamps, and relative spectral responsivity measurements were used to determine the color-temperature correction between the lamps and the Thermogage blackbody. Thermodynamic temperature determinations made using various combinations of apertures and photometers showed a range of less than 0.2 °C at 1700 °C, consistent with the calculated uncertainty of 0.29 °C (k = 2). ITS-90 measurements made by NMIA??s LP5 and HTSP primary radiation thermometers with an uncertainty of 0.16 °C (k = 2), are consistent with the thermodynamic measurements. It is suggested that routine thermodynamic temperature determinations can now be made with an effort comparable to that required to realize the ITS-90 above 1000 °C.     

Development of High-Temperature Blackbodies and Furnaces for Radiation Thermometry

Two high-temperature blackbodies were developed and tested. The first one is a graphite blackbody with a maximum temperature of 2000 °C, an opening of 40 mm, and an emissivity of 0.995. It is intended for the routine calibration of pyrometers. The second one is a small version of a pyrolytic graphite (PG) blackbody with a cavity diameter of 15 mm, an opening of 10 mm, and an emissivity of 0.9996. The blackbody has two options with maximum temperatures of 2500 °C and 3000 °C, respectively. With these, the list of high-temperature blackbodies developed at VNIIOFI consists of five PG types and one graphite type, which can be used in radiation thermometry as precision Planckian sources or furnaces for fixed-point applications. The article also describes modifications to the PG furnace, where PG heater rings are replaced partly or totally by graphite elements. Such modifications extend the lifetime of the heater, reduce the cost for some applications and, for some cases, improve the temperature uniformity.     

关于换热器的低温黑体辐射源

介绍一种工作在-80℃～+100℃的基于换热器的新型低温标准黑体辐射源的设计和其发射率的计算.这种黑体辐射源采用液体恒温槽均温致冷和采用气帘隔离法消除低温凝露和结霜,黑体空腔形状为圆锥圆柱型,锥角为120°,空腔内径50mm,腔长为300mm,控温稳定性优于±0.05℃/30min.理论计算的黑体空腔有效发射率为0.998(保留小数点后三位),比对实验测量得到的有效发射率为0.997(保留小数点后三位),二者接近一致.     

NIST Radiance Temperature and Infrared Spectral Radiance Scales at Near-Ambient Temperatures

The realization and the dissemination of spectral radiance and radiance temperature scales in the temperature range of −50 to 250°C and spectral range of 3–13 μm at the National Institute of Standards and Technology are described. The scale is source-based and is established using a suite of blackbody radiation sources, the emissivity and temperature of which have been thoroughly investigated. The blackbody emissivity was measured using the complementary approaches of modeling, reflectometry, and the intercomparison of the spectral radiance of sources with different cavity geometries and coatings. Temperature measurements are based on platinum resistance thermometers and on the direct use of the phase transitions of pure metals. Secondary sources are calibrated using reference blackbody sources, a spectral comparator, a controlled-background plate, and a motion control system. Included experimental data on the performance of transfer standard blackbodies indicate the need for development of a recommended practice for their specification and evaluation. Introduced services help to establish a nationwide uniformity in metrology of near-ambient thermal emission sources, providing traceability in spatially and spectrally resolved radiance temperature, spectral radiance, and background-corrected effective emissivity.     

Radiation Thermometry Based on Photonic Crystal Fiber

Fiber-coupled radiometry allows for the radiometric measurement of high temperatures in environments where there is no line of sight to the target. However, transmission through conventional silica optical fibers degrades rapidly at elevated temperatures, and exotic fibers??such as sapphire fibers??typically cannot be bent. As part of a project to investigate the performance of solid oxide fuel cells, the feasibility of using an alternative fiber, solid-core silica photonic crystal fiber (PCF), was tested. The test system used an Inconel blackbody as a source, and a detection system based on an InGaAs array spectrometer with a wavelength range of 907 nm to 1681 nm. The temperature was determined from the spectrometer signal at particular wavelengths using the Planck relationship. Two tests were performed: (1) long-term high temperature soak tests to measure the drift and noise in thermal radiation levels, in which spectra are sequentially recorded over a long period of time with the blackbody cavity at a constant temperature and (2) temperature dependence tests, whereby thermal radiation spectra are recorded with the blackbody cavity at several temperatures. At 934 °C, the transmission of the PCF decreased at a rate of 0.078 % per hour corresponding to a temperature error of ?0.12 °C per hour. The transmission of conventional silica fiber decreased at a rate of 0.5 % per hour corresponding to a temperature error of ?0.8 °C per hour. While the PCF represents a significant improvement over conventional fiber, it is still not good enough for most practical purposes. At 600 °C there was no observable decline in transmission and there may be applications for PCF in that regime.     

Low-Temperature Blackbodies for Temperature Range from ?60?��C to 90?��C

Low-temperature cavity-type blackbodies (BB), VTBB and BB100K1, are developed at VNIIOFI for operation as IR radiation sources of the Middle Background Calibration Facility in the temperature range from ?60 °C to 90 °C, which is being constructed by KRISS for calibration of multi-spectral cameras for space applications. The VTBB model, featured by a 30 mm output aperture and hermetic housing and flange for mounting to a vacuum chamber, covers the complete temperature range under a vacuum environment (up to 10^?2 Pa), and the temperature range from 20 °C to 90 °C under open air conditions. BB100K1 has a wide aperture of 100 mm diameter, which shows stable operation in the temperature range from ?60 °C to 90 °C inside a vacuum chamber, and in the temperature range from ?40 °C to 90 °C in a dry-air or inert-gas environment with the usage of an extra hood with an aperture. The effective emissivity of the radiating cavities of both BB, covered with Lord Aeroglaze Z306 black paint, was calculated with the usage of STEEP3 Monte-Carlo simulation software, taking the measured temperature gradients into account. The numerical calculations yield an emissivity of at least 0.9997 for the VTBB cavity, and 0.997 for the BB100K1 cavity. The radiating cavity temperature of VTBB and BB100K1 is stabilized at the level of ±0.01 °C by means of an external precise closed-loop liquid thermostat (Huber Unistat 705 model). The temperature distribution along the radiating cavities and across the BB bottoms is monitored by five precision PRT thermometers and a digital multimeter equipped with a scanner card. Experimental tests using a thermal camera at KRISS demonstrated high-temperature uniformity of both radiation sources not exceeding ±50 mK over the entire temperature range, in vacuum as in a dry-air environment. The combined standard uncertainty of VTBB and BB100K1 temperature measurements accounts for about 40 mK within the range of their working temperatures.     

红外高光谱大气探测仪星载固定点黑体辐射源的研制

介绍了中国计量科学研究院为风云三号05星红外高光谱大气探测仪研制的微型镓固定点星载黑体辐射源。设计了黑体辐射源空腔,其有效发射率优于0.997。针对星载固定点黑体辐射源的结构设计和性能测试展开了研究:星载固定点黑体辐射源17 ℃的温度均匀性仿真结果优于0.01℃;黑体辐射源在真空下均匀性优于0.02 ℃,稳定性优于0.002 ℃(90 min内);在通过满足航天应用的力学冲击等实验后,镓固定点的复现性优于0.03 ℃;微型固定点相变温坪复现实验加热功率与拐点值之间存在较好的线性关系。     

Experiences in Calibrating Industrial Platinum Resistance Sensors Between − 196 °C and 80 °C

Recently, a requirement arose to provide sensors for measuring the temperature of a substantial reference blackbody cavity to operate in vacuum over a temperature range from ? 100 °C to 80 °C (~?170 K to ~?350 K), with an additional capability to operate at ~? 170 °C (~?100 K) as a point of near-zero radiance. Several 100 Ω industrial platinum resistance sensors (Pt100) are required for control purposes in order to establish the temperature uniformity of the blackbody structure and its surrounding aluminum-alloy isothermal shield. These sensors should remain stable within the uncertainties of 0.03 °C (k?=?3) ideally for 20 years. This paper discusses the testing and calibration of two types of industrial Pt100 resistors, including checking the interchangeability of sensors from a given batch, and the methods of interpolation over the temperature range. It is concluded that the sensors can meet the requirements provided that they have been individually tested, and that there is a degree of duplication of sensors so that long-term changes can be detected. The calibration data could be fitted by cubic or quartic equations expressing temperature as a function of resistance (or resistance ratio), this being simpler than the ITS-90 formulation and more convenient than using the (technically obsolete) Callendar–Van Dusen equation.     

中温区真空标准黑体辐射源研制

介绍了中国计量科学研究院研制的中温区真空标准黑体辐射源的结构设计,工作原理,测试结果和不确定度评定.黑体辐射源工作温度范围为320～500 K,黑体空腔开口直径为50 mm,空腔深度为260 mm,表面喷涂了耐高温漆,空腔发射率优于0.999.真空环境下测试了黑体在335～500K温度范围内的轴向温度均匀性,温度稳定性...     

真空汞固定点黑体辐射源的设计与研制

介绍了中国计量科学研究院研制的真空汞固定点黑体辐射源的结构、工作原理、性能测试结果和不确定度分析。真空汞固定点黑体辐射源灌注的是纯度为99.9999%的高纯汞,黑体空腔开口直径为25 mm,空腔内径为28 mm,深度为260 mm,表面喷涂了NEXTEL 811-21高发射率涂层,采用基于蒙特卡罗黑体发射率仿真计算的方法,计算了黑体空腔在波长为8~14μm的发射率,结果优于0.9999;在真空环境下,测试了真空汞固定点黑体辐射源的温坪曲线和重复性等主要技术指标,结果表明真空汞固定点黑体辐射源温坪稳定性优于2 mK,多次重复性优于1 mK;分析了真空汞固定点黑体辐射源的不确定度来源,其合成标准不确定度为16 mK。     

低温标准黑体辐射源的性能研究

利用半导体制冷技术与热管技术,研制了低温达-30 ℃的新型低温黑体辐射源。通过实验得到其温度稳定性优于0.02 ℃/20min,均温区腔壁的轴向温度均匀性优于0.3 ℃,热管空腔有效发射率计算值大于0.999 2。利用基于光线跟踪技术的Monte Carlo方法,计算得出该热管空腔发射率从中心到边缘位置的变化规律为逐渐减小的趋势,发射率的平均变化率仅为0.06‰,说明轴向温场均匀性对法向平均有效发射率的影响较小。     

Measurement and Analysis of the Temperature Gradient of Blackbody Cavities,for Use in Radiation Thermometry

Blackbody cavities are the standard radiation sources widely used in the fields of radiometry and radiation thermometry. Its effective emissivity and uncertainty depend to a large extent on the temperature gradient. An experimental procedure based on the radiometric method for measuring the gradient is followed. Results are applied to particular blackbody configurations where gradients can be thermometrically estimated by contact thermometers and where the relationship between both basic methods can be established. The proposed procedure may be applied to commercial blackbodies if they are modified allowing secondary contact temperature measurement. In addition, the established systematic may be incorporated as part of the actions for quality assurance in routine calibrations of radiation thermometers, by using the secondary contact temperature measurement for detecting departures from the real radiometrically obtained gradient and the effect on the uncertainty. On the other hand, a theoretical model is proposed to evaluate the effect of temperature variations on effective emissivity and associated uncertainty. This model is based on a gradient sample chosen following plausible criteria. The model is consistent with the Monte Carlo method for calculating the uncertainty of effective emissivity and complements others published in the literature where uncertainty is calculated taking into account only geometrical variables and intrinsic emissivity. The mathematical model and experimental procedure are applied and validated using a commercial type three-zone furnace, with a blackbody cavity modified to enable a secondary contact temperature measurement, in the range between 400 °C and 1000 °C.     

Use of a High-Temperature Integrating Sphere Reflectometer for Surface-Temperature Measurements

The National Institute of Standards and Technology (NIST) has developed a new facility for the characterization of the infrared spectral emissivity of samples between 150 and 1,000°C. For accurate measurement of the sample surface temperatures above 150°C, the system employs a high-temperature reflectometer to obtain the surface temperature of the sample. This technique is especially useful for samples that have significant temperature gradients due to the thermal conductivity of the sample and the heating mechanism used. The sample temperature is obtained through two measurements: (a) an indirect sample emissivity measurement with an integrating sphere reflectometer and (b) a relative radiance measurement (at the same wavelengths as in (a)) of the sample as compared to a blackbody source. The results are combined with a knowledge of the blackbody temperature and Planck’s law to obtain the sample temperature. The reflectometer’s integrating sphere is a custom design that accommodates the sample and heater to allow reflectance measurements at temperature. The sphere measures the hemispherical-near- normal (8°) reflectance factor of the sample compared relative to a previously calibrated room-temperature reference sample. The reflectometer technique of sample temperature measurement is evaluated with several samples of varying reflectance. Temperature results are compared with values simultaneously obtained from embedded thermocouples and temperature-drop calculations using a knowledge of the sample’s thermal conductivity.     

Comparison Measurements of Infrared Ear Thermometers Against Three Types of Blackbody Sources

Body temperature is a basic vital sign of the human body, and the use of infrared ear thermometers for medical diagnosis and health management on human bodies has been widespread nowadays. To gain credibility and confidence in the usage of IR ear thermometers, a standard blackbody source (BBS) with a calibration traceable to ITS-90 is necessitated. Three types of cavity-shaped blackbodies (designated BBC-A, BBC-E, and BBC-J) vertically immersed in a temperature-controlled stirred water bath were developed at the Center for Measurement Standards (CMS) as standard BBSs to calibrate and verify 14 commercial IR ear thermometers produced by six manufacturers. The basic structure of each cavity was designed based on the informative examples recommended in ASTM E-1965, EN 12470-5, and JIS T 4207 standards. The temperature of the blackbody cavity shall be represented by the water temperature near the bottom of the cavity that is measured using an immersed platinum resistance thermometer (PRT) for which the calibration is traceable to our national standard and with an uncertainty no greater than 0.03 °C (k = 2). The water bath was evaluated using the PRT to be stable within ±3.5 mK over 1 h and uniform within ±1.1 mK. Three types of BBSs were compared and analyzed utilizing two IR ear thermometers of 0.01 °C resolution as well as the statistical technique of analysis of variance (ANOVA). On the contrary, IR ear thermometers were tested and verified against three BBSs at three blackbody temperatures of 35.5 °C, 37 °C, and 41 °C. The analysis results of ANOVA showed that there is no significant temperature difference among three different structured blackbodies, and the average measured radiance temperature of three BBSs at 35.5 °C, 37 °C, and 41 °C were within 0.026 °C, 0.024 °C, and 0.027 °C of each other. Three among fourteen IR ear thermometers tested were outside of the 0.2 °C MPE (maximum permissible error) recommended by ASTM E-1965, EN 12470-5, or JIS T 4207 standards while BBC-A and BBC-E were used; however, four were outside of MPE requirement when BBC-J was used.     

Radiation Thermometry and Emissivity Measurements Under Vacuum at the PTB

A new experimental facility was realized at the PTB for reduced-background radiation thermometry under vacuum. This facility serves three purposes: (i) providing traceable calibration of space-based infrared remote-sensing experiments in terms of radiation temperature from  −173 °C to 430 °C and spectral radiance; (ii) meeting the demand of industry to perform radiation thermometric measurements under vacuum conditions; and (iii) performing spectral emissivity measurements in the range from 0 °C to 430 °C without atmospheric interferences. The general concept of the reduced background calibration facility is to connect a source chamber with a detector chamber via a liquid nitrogen-cooled beamline. Translation and alignment units in the source and detector chambers enable the facility to compare and calibrate different sources and detectors under vacuum. In addition to the source chamber, a liquid nitrogen-cooled reference blackbody and an indium fixed-point blackbody radiator are connected to the cooled beamline on the radiation side. The radiation from the various sources is measured with a vacuum infrared standard radiation thermometer (VIRST) and is also imaged on a vacuum Fourier-transform infrared spectrometer (FTIR) to allow for spectrally resolved measurements of blackbodies and emissivity samples. Determination of the directional spectral emissivity will be performed in the temperature range from 0 °C to 430 °C for angles from 0° to ±70° with respect to normal incidence in the wavelength range from 1 μm to 1,000 μm. References to commercial products are provided for identification purposes only and constitute neither endorsement nor representation that the item identified is the best available for the stated purpose.