What are the primary standards used for temperature calibration?

Temperature calibration references include: ITS-90 fixed points (triple points, freezing/melting points of pure materials - e.g., water triple point 0.01 degrees C, zinc freezing 419.527 degrees C), dry block calibrators (portable, -25 to 700 degrees C), oil/sand baths (for immersion calibration), ice baths (0 degrees C reference), and standard platinum resistance thermometers (SPRTs) as transfer standards. Traceability to national standards (NIST, PTB) through calibration chain ensures measurement accuracy.