They are capable of being used to directly measure temperatures up to 2600ºC; and
The junction of the thermocouple can be grounded and brought into direct contact with the measured material.
Disadvantages of thermocouples:
Temperature measurement with a thermocouple involves the measurement of two temperatures, the junction at the end of the job (hot junction) and the junction at which cables meet the copper cables of the apparatus (cold junction). To avoid error, the cold junction temperature is in general compensated in the electronic instruments by measuring the temperature at the terminal block using a semiconductor, thermistor, or RTD
Thermocouple activities with prospective sources of mistake are comparatively complicated. The materials from which thermocouple cables are produced are not inert and corrosion can influence the thermoelectric voltage created along the thermocouple wire length, etc.
The process temperature connection with the thermocouple signal is not linear ;
The thermocouple calibration must be performed while in use by comparing it with a nearby thermocouple comparison. If the thermocouple is removed and placed in a calibration bath, it does not exactly reproduce the output integrated over the length