The conductors in Extension grade Thermocouple cables have a smaller temperature range than do thermocouple grade conductors. It must be noted that the temperature range that is being referred to here is with respect to a thermocouple junction meeting the ISA/ANSI requirements for limits of error. If the conductors in a cable are not forming a thermocouple junction, then there is no performance difference between the two. Also, in all cases, the maximum temperature rating of the cable is less than the thermocouple junction rating. The cable temperature rating must never be exceeded.
Belden makes a wide variety of cables in types E, J, K, T, EX, JX, KX, TX. We do no make types B, R, or S.