The straight base metal thermocouple elements illustrated below are replacement elements for use in complete industrial thermocouple assemblies. These replacement elements are also compatible for use in other manufacturers’ thermocouple assemblies. These thermocouples are available as bare wire or ceramic insulated thermocouple elements, with options as listed below, and with special construction designs.
Base metal thermocouples are known as Types E, J, K, T and N and comprise the most commonly used category of Thermocouple. The conductor materials in base metal thermocouples are made of common and inexpensive metals such as Nickel, Copper and Iron.
Type E: The Type E thermocouple has a Chromel (Nickel-10% Chromium) positive leg and a Constantan (Nickel- 45% Copper) negative leg. Type E has a temperature range of -330 to 1600° F, has the highest EMF Vs temperature values of all the commonly used thermocouples, and can be used at sub-zero temperatures. Type E thermocouples can be used in oxidizing or inert atmospheres, and should not be used in sulfurous atmospheres, in a vacuum or in low oxygen environments where selective oxidation will occur. The color code for TYPE E wire is purple and red.
Type J: The Type J thermocouple has an Iron positive leg and a Constantan negative leg. Type J thermocouples can be used in vacuum, oxidizing, reducing and inert atmospheres. Due to the oxidation (rusting) problems associated with the iron leg, care must be used when using this thermocouple type in oxidizing environments above 1000° F. The temperature range for Type J is 32 to 1400° F and it has a wire color code of white and red.
Type K: The Type K thermocouple has a Chromel positive leg and an Alumel (Nickel- 5% Aluminum and Silicon) negative leg. Type K is recommended for use in oxidizing and completely inert environments. Because it’s oxidation resistance is better than Types E, J, and T they find widest use at temperatures above 1000° F. Type K, like Type E should not be used in sulfurous atmospheres, in a vacuum or in low oxygen environments where selective oxidation will occur. The temperature range for Type K is -330 to 2300° F and it’s wire color code is yellow and red.
Type N: The Type N thermocouple has a Nicrosil (Nickel-14% Chromium- 1.5% Silicon) positive leg and a Nisil (Nickel- 4.5% Silicon- .1% Magnesium) negative leg. Type N is very similar to TYPE K but is less susceptible to selective oxidation effects. Type N should not be used in a vacuum or in reducing atmospheres in an unsheathed condition. The temperature range is 32-2300 deg F and its wire color code is orange and red.
Type T: The Type T thermocouple has a Copper positive leg and a Constantan negative leg. Type T thermocouples can be used in oxidizing, reducing or inert atmospheres, except the copper leg restricts their use in air or oxidizing environments to 700° F or below. The temperature range for Type T is -330 to 700° F and it’s wire color code is blue and red.