The Thermocouple Compensating and Extension Grade Alloys are used for connecting thermocouples to temperature indicating instruments the best way is to use the leads made of same material. JLC Electromet Pvt. Ltd. Offers Thermocouple Compensating and Extension Grade Alloys. JLC Electromet Pvt. Ltd. An ISO 9001:2008 certified company that supplies Nickel and Nickel based specialty alloys in wire, strip and ribbon forms. These Thermocouple Compensating and Extension Grade Alloys leads which have same emf output as the thermocouple itself are called extension leads. Extension leads avoid lead junction error. However, for Economic reasons, cheaper alloys having similar emf output over a limited temperature range [generally 200 Deg C] are often used.