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

Abstract

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 µm to 15 µm. 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.

A $${-}30\,^{\circ }\hbox {C}$$ - 30 ∘ C to $$80\,^{\circ }\hbox {C}$$ 80 ∘ C Stirred-Liquid-Bath-Based Blackbody Source

“…The diameter of previously reported blackbody apertures is less than 110 mm (typically 60 mm) [2][3][4][5][6][7]. In the present study, the aperture diameter and the expected effective emissivity of the SLBB are 80 mm and 0.9998, respectively.…”

“…The radiance temperature given by these instruments should be traceable to the international temperature scale of 1990 B J. Wang wangjh@nim.ac.cn 1 (ITS-90) [1,2]. A variable-temperature blackbody (VTBB) source is often used to transfer the radiation-temperature scale to custom infrared thermometers as reference radiation sources.…”

“…The temperature of these blackbodies should be directly traceable to ITS-90 using a contact thermometer or a radiation thermometer [3]. Many standard VTBBs have been developed in national metrology institutes around the world [2][3][4][5][6][7].…”

Design, Fabrication, and Performance Evaluation of Portable and Large-Area Blackbody System

“…However, extremely few researchers have investigated this type of portable and large-area blackbody system required for aerial infrared thermal imaging technology. Moreover, there has been negligible research on the development and evaluation of such portable and large-area blackbody systems worldwide [ 25 , 26 , 27 , 28 ].…”

“…The temperature uniformity of the water volume is ±2.0 mK at the lowest temperature in its operating range and ±5.0 mK at the high end of its operating range of 278 to 353, as measured using the resistance thermometry. Park et al [ 27 ] constructed a large aperture blackbody 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°.…”