The Gemini R 550 Portable Blackbody Calibration Source allows for calibration of noncontact infrared thermometers over the temperature range 30°C to 550°C. It is suitable for use as a primary radiation source for infrared thermometers. Laboratory performance and low uncertainty calibrations are ensured by the combination by high emissivity and excellent temperature uniformity. The digital temperature controller allows the block temperature to bet set to any value from 30°C to 550°C. Traceability of the radiance temperature is established by a separate, built-in temperature indicator and included platinum resistance thermometer. A three point traceable calibration certificate is included. UKAS calibration of the resistance thermometer is available, as is radiometric calibration. Uniformity of the block is ensured by using distributed heating technology. For the smallest of uncertainties the Gemini R may be used with Isotech ITS-90 Fixed Point Cells, Gallium 29.7646°C, Indium 156.5985°C, Tin 231.928°C and Zinc 419.527°C. The cells are provided with a certificate of metal purity.