Thermocouple sensors

A thermocouple is a temperature measuring device consisting of two conductors of dissimilar metals or alloys that are connected only at the ends. When the ends are at different temperatures, a small voltage is produced in the wire that can be related directly to the temperature difference between the ends. If the temperature at one end is known, the temperature at the other end can be determined.

Thermocouple wire or extension grade wire is used to connect the thermocouple to the sensing or control instrumentation. The conditions of measurement determine the type of thermocouple wire and insulation to be used. Temperature range, environment, insulation requirements, response, and service life should be sonsidered when selecting a wire type.

Different thermocouple types (e.g. K, T, N, J, etc) are made from different combinations of metals. There are two common types of thermocouple wire, Type J and Type K. The J Type is made from Iron and another slightly different copper-nickel alloy and the K Type thermocouple has a Nickel-Chromium positive conductor and a Nickel-Aluminum negative conductor.

Type K thermocouples are used in oxidizing, inert or dry reducing atomspheres. Exposure to vacuum is limited to short time periods. Must be protected from sulfurous and marginally oxidizing atmospheres. Reliable and accurate at high temperatures.