How do thermocouple measure good or bad

Thermocouple in use after a period of time, there will be wear and tear, and may even be damage, individual thermocouple pros and cons and its outside thermocouple wire (wire), but how to determine the pros and cons of thermocouple, the following is a brief overview of how to determine the pros and cons of thermocouple:

First determine the surface of the thermocouple line is not good or bad, through the process of detection ability to determine.
The thermocouple line to be tested is put on the common porcelain sleeve of the thermocouple, and put into the tubular electric furnace together with the scale platinum rhodium thermocouple. The hot end is pulled out of a cylinder made of porous metal nickel for heat distribution in the tubular electric furnace. Place the cold ends of the respective complementary wires into a zero degree container held by the ice water mixture.

Adhere to the tube furnace at the lowest allowable temperature of the thermocouple, and firmly adhere to this category. This time through the detection of Wheisden potential difference meter, measured the scale thermocouple and the thermocouple to be measured and recorded the thermoelectric potential difference.

According to the recorded thermoelectric potential difference, check the thermometer to find out the corresponding temperature, if the thermocouple to be measured out of tolerance, can be determined as a divergent lattice.