Thermocouple Compensating and Extension Grade Alloys :

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 thermoelements so joined as to produce a thermal emf when the junction 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.

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 sameemf 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

Theemf 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 foremf and value of deviation from the standardemf 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)

Type of Thermocouple	T Cu-Constantan			J Iron-Constantan			E K1-Constantan			K K1-K2
Positive Leg.	Copper			Iron			K1			K1
Negative Leg.	Constantan			Constantan			Constantan			K2
Temprature (°C)	EMF (mV)	Tolerance		EMF (mV)	Tolerance		EMF (mV)	Tolerance		EMF (mV)	Tolerance
		°C	%		°C	%		°C	%		°C	%
-200 °C	-5.603	±1	±1.5	-			-	±1.7	±1	-	±2.2	±2
-100 °C	-3.378			-			-			-
0 °C	0.000	±1	±0.75	0.000			0.000			0.000
100 °C	4.277			5.268	±2.2	±0.75	6.317	±1.7	±0.50	4.095	±2.2	±0.75
200 °C	9.286			10.777			13.419			8.137
300 °C	14.860			16.325			21.033			12.207
400 °C	20.869			21.846			28.943			16.395
500 °C				27.388			36.999			20.640
600 °C				33.096			45.058			24.902
700 °C				39.130			53.110			29.128
800 °C				45.498			61.022			33.277
900 °C							68.783			37.325
1000 °C										41.269
1100 °C										45.108
1200 °C										48.828
1300 °C										52.398

Table-2: JLC Extension and Compensating Alloys (According to AST E230 AND ANSI MC96.1)

Thermocouple	Compensating or extension cables	Composition	AMERICAN SPECIFICATION (ANSI MC96.1)
			mV	at temp. °C	Tolerance
					Standard	Special
K1-K2 (Type K)	K1-K2 (KX)	K1:Ni,Kr K2:Ni,Al	4.095 8.137	100 200	±2.2°C From 0°to 200°C	...... ......
K1-K2 (Type K)	Cu-ConstantanV (VX)*	Cu:100% Cu Constantan:Ni,Cu	4.095 .......	100 ......	±2.2°C From 0°to 200°C	...... ......
K1-ConstantanE (Type E)	K1-ConstantanE (EX)	K1:Ni,Kr Constantan:Ni,Cu	6.317 13.419	100 200	±1.7°C From 0°to 200°C	...... ......
Cu-ConstantanT (Type T)	Cu-ConstantanT (TX)	Cu:100% Cu Constantan:Ni,Cu	........ 4.277	0 100	±1°C From 0°to 100°C	±0.5°C  0°C to 100°C
Fe-Constantan J (Type J)	Fe-Constantan J (JX)	Fe:100% Fe Constantan:Ni,Cu	5.268 10.777	100 200	±2.2°C From 0°to 200°C	±1.1°C  0°C to 100°C
Pt-Pt10%Rh Pt-Pt13%Rh (Type S,R)	Cu-Cu Ni 3 (SX)(RX)	Cu: 100%Cu Cu Ni3 :Cu,Ni	0.645 1.440	100 200	±0.057 mV From 0°to 200°C	...... ......

^*Type VX is not included in American Specification