Tempco Custom Heater Manufacturing

Thermocouple Extension Wire Color Codes & Specifications

For United States, Canada & Mexico

ANSI Code ANSI Color Code Positive
(+) Lead
(-) Lead
Temperature Range Initial Calibration Tolerances
Standard Special
JX Type JX Iron Constantan
(45% Nickel,
55% Copper)
32-392°F (0-200°C) ±2.2°C ±1.1°C
KX Type KX Chromel®
(90% Nickel,
10% Chromium)
(95% Nickel,
2% Aluminum,
2% Manganese,
1% Silicon)
32-392°F (0-200°C) ±2.2°C ±1.1°C
EX Type EX Chromel®
(90% Nickel,
(45% Nickel,
32-392°F (0-200°C) ±1.7°C ±1.1°C
TX Type TX Copper Constantan
(45% Nickel,
32 to 212°F (0-100°C) ±1.0°C ±0.5°C
NX Type NX Nicrosil
(84.6% Nickel,
4% Chromium,
1.4 % Silicon)
(95.6% Nickel,
4.4 % Silicon)
32-392°F (0-200°C) ±2.2°C ±1.1°C
Compensating Extension Wire Type
RX* Type RX Copper Copper Alloy 32-392°F (0-200°C) ±9°F
SX* Type SX Copper Copper Alloy 32-392°F (0-200°C) ±9°F
BX* Type BX Copper Copper 32 to 212°F (0-100°C) +0°F  (+0°C)
–6.7°F (–3.7°C)


* Due to the non-linearity of the types R, S, and B temperature-emf curves, the error introduced into a thermocouple system by the compensating wire will be variable when expressed in degrees. The degree C tolerances are based on the following measuring junction temperatures.

Type Wire Measuring Junction Temperature
SX Greater than 1598°F (870°C)
BX Greater than 1832°F (1000°C)

 Copper versus copper compensating extension wire, usable to 100°C (212°F) with maximum deviations as indicated, but with no significant deviation over 0°C to 50°C (32°F to 122°F) range.

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Tempco Electric Heater Corporation

607 N. Central Ave. | Wood Dale, IL 60191-1452 USA
Phone: 630.350.2252 | Toll Free: 888.268.6396
Fax: 630.350.0232 | Email: [email protected]

We have Branch Offices located across the United States.



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