The defining instruments of the ITS-90 (International Temperature Scale of 1990) are Standard Platinum Resistance Thermometers (SPRTs) and ITS-90 fixed-point cells. SPRTs are calibrated in fixed-point cells to provide the highest possible temperature accuracy.
Primary standards offered by Fluke Calibration include: long-stem SPRTs; capsule SPRTs; triple point of water cells; metal fixed-point cells; maintenance baths and maintenance furnaces for fixed-point cells; standard resistors.