1.1 This test method covers the techniques of thermocouple calibration based upon comparisons of thermocouple indications with those of a reference thermometer, different from methods involving the use of fixed points. The precise evaluation of the electromotive force (emf)-temperature relation of a thermocouple is accomplished by determining its emf output at each of a series of measured temperatures. Calibrations are covered over temperature ranges appropriate to the individual types of thermocouples within an over-all range from about -180 to 1700°;C (-290 to 2660°;F). 1.2 In general, the test method is applicable to bare wire thermocouples or sheathed thermocouples. The latter may require special care to control thermal conduction losses.