What is the thermocouple cold end temperature compensation?

What is the thermocouple cold end temperature compensation? Because the data of thermocouple are generally more expensive, especially when choosing the precious metals, and the interval of temperature measuring points to the instrument are far away, in order to save thermocouple data, reduce capital, usually adopt the compensating conductor (of the cold junction of the thermocouple Free end) Extended to the steady control of indoor temperature compare with, cohesion to the meter terminals.

must be pointed out that the role of the thermocouple compensation wire only extend thermal electrode, make the move to the control room of the cold junction of the thermocouple meter terminal on its own does not eliminate the cold end temperature change on the influence of temperature, no compensation. So, still need to use other correction method to compensate of the cold end temperature t0 indicates influence on measuring temperature 0 ℃.