Thermocouple Compensating and Extension Grade Alloys

Material Description

JLC produces a wide range of thermocouple materials that are used to manufacture thermocouples, extension and compensating wires/cables. At JCL, we start with right selection of best available raw material to achieve the required chemical composition. A correct chemical composition is necessary to give uniform and exact thermocouple properties. The alloys are melted, hot-rolled and processed to final sizes using state-of-the-art technology. JLC believes in continuous improvement; all the processes are constantly monitored at each step using statistical process control tools to ensure the best quality of the final products.

The information on different grades of JLC thermocouple alloys is provided in this page. If you need further technical information, our team of engineers and technical staff are always available to assist you

Thermocouple Grade

Thermocouples are formed by two dissimilar thermo elements so joined as to produce a thermal emf when the junctions are at different temperature. The different grades of thermocouples alloys are used depending upon temperature being measured, working atmosphere and characteristics of physical atmosphere. JLC produces various grades of thermocouples wires and strips as per international specifications. The properties and emf tolerances for these grades of JLC thermocouples are shown in Table-1. K1 & K2 alloys, each individual is calibrated against platinum and a certificate on the label of each coil shows the deviation from standard values to be calculated. All thermocouples supplied in bright annealed condition.

Thermocouple Compensating and Extension Grade Alloys

For connecting thermocouples to temperature indicating instruments the best way is to use the leads made of same material. These 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 °C) are often used. These leads are called COMPENSATING LEADS.

JLC offers a full range of material for Extension/Compensating leads. The different grades of these materials and the emf tolerance for these grades over a required temperature range are shown in Table-2.

Standard Specification

JLC range of thermocouple alloys meets the specification of ASTM E 230 and ANSI MC 96.1. JLC thermocouple alloys also confirm to IS, IEC, DIN, BS, NF, UNI, ENI, JIS, ENEL and GOST standard. Thermocouple alloys for Mineral Filled Sheathed cables are made confirming to ASTM E 608 and ASTM E 585. Special tolerance and properties are made available on customer request.

Standard and Special Grades

The emf tolerance of standard grade of alloys is according to the Tables 1 and 2. Our special grades offer closer tolerances (½ and ¼ of standard grades) for applications where higher accuracy is needed.

Surface Finish

JLC thermocouple wires/strips are offered in bright annealed condition. However, oxidized wire surface is also available for applications where corrosive atmosphere is present.

Calibration

JLC thermocouple grades are calibrated over the temperature range according to international specifications. All our grades are individually calibrated versus NBS Pt 67. Each coil/spool is tested for emf and value of deviation from the standard emf at different temperatures is shown on the labels attached to each coil/spool. All JLC thermocouple materials are made confirming to emf/temperature requirements for thermocouples as per NBS monograph 125.

Available Sizes

JLC thermocouple materials are available in different sizes (mm/AWG/SWG) or resistance based upon customer's requirement. Most common available sizes range from 8.255 mm (0 AWG) to 0.142 mm (35 AWG), in addition to strips/ribbons in various sizes.

Final Inspection and Testing

Each spool/coil of JLC thermocouple, extension and compensating alloy is calibrated according to specifications given above. JLC thermocouple alloys are fully tested for homogeneity of chemical composition, physical and thermoelectric properties before leaving the factory. This includes the testing of electrical resistivity (loop resistance), which is an important property of thermocouple alloys.

Table-1: JLC Thermocouple Alloys (According to AST E230 and ANSI MC96.1)