Title: Development of the calibration system for very accurate thermometers at low temperatures
Abstract: For the accurate calibrations of thermometers at low temperatures, triple points of oxygen and argon have been realized using sealed-type triple point cells. The triple points were realized with both adiabatic and continuous heating methods. The resistance of three capsule-type standard platinum resistance thermometers were measured at the triple points of oxygen, argon, mercury and water for the calibrations of these thermometers in the range from <TEX>$-220^{\circ}C$</TEX> to <TEX>$0.01^{\circ}C$</TEX>. The extended uncertainty, with the coverage factor of 2, of the calibration in this range is smaller than 1 mK.