Thermocouples, Thermocouples Materials and Thermometer Indicators(32010C-32147C) Calibration services for all commonly used types of Thermocouples are provided by NIST from -196 °C to 1750 °C depending upon the wire or Thermocouples type. The Thermocouples are calibrated by one or a combination of three general methods, depending on the Thermocouples type, the temperature range, and the uncertainty required. All three methods provide traceability to the ITS-90. In the first method,　Thermocouples are calibrated by comparison with a reference　Thermocouples maintained at NIST. In the second method, Thermocouples are calibrated by comparison with a standard platinum resistance　thermometer. In the third method, Thermocouples are calibrated at　four defining fixed-point temperatures on the ITS-90: the freezing　points of Zn, Al, Ag, and Au. Below 0 °C, the thermocouple　calibration is performed in a cryostat; above 0 °C, stirred liquid　baths, metal freezing-point cells, and electric tube-type furnaces　re employed for the calibrations. Vacuum or inert gas furnaces are　also available for testing thermocouples.　Only the bare wires are required to perform the thermocouple　calibrations. It is preferable not to send insulating and protecting　tubes as the rate of breakage of these in shipment is high. If the　thermocouple is furnished mounted (as in a protection tube　assembly), a nominal charge will be made for dismantling the　mounting and the various parts will be returned to the sender　without reassembling them. Minimum thermocouple length requirement　listed in the Service ID Number tables are exclusive of lead wire. 　Lead wires (for connections) should not be sent with thermocouples.　All thermocouple calibration data furnished in reports will be on　the basis of a reference junction temperature of 0 °C (32 °F). The 　calibration results will be given in °C or °F, as requested by the　customer. The calibration of a thermocouple will not be undertaken　if it will likely not yield the specified expanded uncertainty or if　it possesses unusual characteristics that would prevent the　performance of the calibration or test at a reasonable cost. Only　unused base-metal thermocouples and thermocouple materials will be　accepted for test.　All uncertainties are expressed as expanded uncertainties and vary　with test temperature. In cases where a range of temperatures is　given, the stated expanded uncertainty is the maximum of the
expanded uncertainties over this range of temperatures. 　back to top | back to index of thermodynamic quantities　Special Tests of Thermocouples and Thermocouple Materials (32150S)　For requirements not covered by calibrations described above,　special arrangements may be made by consulting one of the specified　staff members.