Development and characterisation of a bath-based vertical blackbody cavity calibration source for the range −30 °C to 150 °C

Industrial use of Radiation Thermometers (RTs) is becoming increasingly common due to the perceived advantages and wide market availability. Blackbody Cavity Radiation Sources (BCRSs) are typically used for calibration of these instruments, and these cavities are oriented horizontally in most cases. For BCRSs based in thermal baths, this necessitates the use of custom-built baths with side openings. This paper presents a unique design of vertical bath-based BCRS that may be immersed in conventional calibration baths without modifications to the baths. The method, results, and analysis of an international comparison comparing this vertical BCRS, standard horizontal BCRSs, and a previous iteration of the vertical design of BCRS are also presented. The comparison was conducted through collaboration between the Laboratory of Metrology and Quality, Slovenia (LMK) and the National Standards Authority Ireland (NSAI), with the intention of evaluating the suitability of the vertical orientation for calibration work. Transfer pyrometers and Standard Platinum Resistance Thermometers (SPRTs) were used as comparison standards. The transfer pyrometers used have spectral sensitivity from 8 μm to 14 μm in this temperature range. It was found that the vertical orientation was comparable to within 0.25 °C throughout the range to standard horizontal cavities. It was concluded that a vertical configuration is an economical alternative for calibration of RTs within the range assessed.