。 By thermocouple indexing, B, S, K, E, etc. The temperature of the thermocouple and the millivolt ( MV） The value of the corresponding relation, the same temperature condition, the onset of millivolt values ( MV） B the minimum degree, S degree, small, K index number is larger, E index number is the largest, follow this principle to distinguish. By analyzing certified the thermocouple is unqualified, in use of this phenomenon is unknown, not make people pay attention to. Incur the thermocouple calibration qualified in the use of unqualified phenomenon is mainly because of the influence of wire thermocouple accidentally heterogeneity, armoured thermocouple shunt error and improper using thermocouple formation, electrician learning the secrets of the small make up in this paper are read. Thermocouple wire heterogeneity heterogeneity effect (1) thermocouple material itself. Thermocouple in the measuring room verification, according to the regulations request, insert the thermocouple calibration furnace to a depth of 300 mm. Each thermocouple calibration results, therefore, to be exact only performance or mainly show the beginning from the measurement of 300 nm long accidentally silk thermal behavior. However, when the length of the thermocouple is longer, when using large local accidentally SiDou at high temperature, if the thermocouple wire heterogeneity and in place of temperature gradient, then the part will produce thermoelectric emfs. The electromotive force called parasitic potential, potential provoked by a parasitic error is called homogeneous. Thermocouple wire after using the heterogeneity. About the new system of thermocouple and even heterogeneity performance to satisfy the request, however, repeated machining, bending the thermocouple produce distortion, will also lose homogeneity, and use of thermocouple under high temperature for a long time, will be provoked by accidentally silk degradation thermoelectric emfs. When local is part of the degradation temperature gradient, also will produce the parasitic potential superposition in total thermoelectric DongShiZhong and presents the measurement error.