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Abstract

The HSBB, which has been developed at PTB in recent years, is a new reference blackbody specifically designed for the calibration of infrared radiometers with a hemispherical acceptance angle such as pyrgeometers, IRIS or ACP instruments. The HSBB is a transportable reference instrument typically operated in the temperature range of ‑20 °C to 20 °C. Using the HSBB, it was recently possible to validate the traceability of the Tilted Bottom Cavity BB2007 operated at PMOD/WRC, the established worldwide reference for longwave downward radiation measurements. New measurements performed using the HSBB are reported in this work. To approve the applicability of the HSBB for future calibration of radiometers measuring longwave downward radiation, different measurements with varying operating parameters like detector distance or purge rate were performed in cooperation with the DWD. As a result of these measurements, improved calibration procedures have been developed and different opening angles of the investigated radiometers have been identified.Clinical infrared ear thermometers also have large opening angles. As the calibration and testing of these devices is strictly regulated in most countries, high-quality reference blackbodies are required. At PTB, the suitability of the HSBB to act as a reference blackbody for ear thermometer testing has been validated, which is a further critical test for its applicability.An additional HSBB with an advanced CNT-based coating has also been put into operation. Direct comparison measurements were successfully performed between both HSBBs. Activities related to the HSBB took place within a Metrology for Earth Observation and Climate (MetEOC) project.