Type K vs. Type J Thermocouple Wire: Which One To Buy?
Type K vs. Type J Thermocouple Wire: Which To Buy?
When choosing a thermocouple wire, the most common choice is between Type K and Type J, as they are versatile, equally reliable, and suitable for a larger number of applications than more niche variations of a thermocouple wire.
What Is A Type K Thermocouple Wire?
Type K is a thermocouple wire with a temperature range of –270°C to 1260°C. The two conductors are nickel/chromium alloy, known under the name chrome, and nickel/aluminum alloy, or alumel.
- This is a cheaper thermocouple wire that also has excellent protection from oxidation. Therefore, type K wire is perfect for use in harsh environments where oxidation is possible, as well as outside.
- Because of its oxidation properties, Type K thermocouple wire lasts longer than Type J thermocouple. Type K is a fast-response type thermocouple, which means that it is excellent at measuring the temperatures of surfaces and liquids.
What Is Type K Thermocouple Used For?
Type K thermocouple wire is commonly used in applications with a temperature rating of 550 °C and above. The maximum operating temperature is 1100 °C. Usually, the applications of a type K thermocouple wire fall into this range.
Some of the common applications are:
- Steel Plants and Iron Plants. Here, Type K thermocouple wires are used to keep track of the temperatures in the process of casting steel and iron.
- Chemical Refineries - to test temperatures.
- Petroleum Facilities - to test temperatures.
- Nuclear Plants - a type K thermocouple is radiation hardened, which means its susceptibility to radiation impact is lower than other similar materials.
Type K thermocouple wire is not suitable for vacuum-like applications and sulphuric conditions because of the properties of chromel and alumel in these environments.
What Is A Type J Thermocouple Wire?
Type J is a thermocouple wire with two conductors, one made of iron and another one made of constantan ( Copper-Nickel ) alloy wire. The temperature range of the cable is -40°C to 750°C because iron cures at a higher point. It is cheaper than Type K thermocouple wire, though both are in the lower price range than other types of thermocouple grade wire.
- Type J Thermocouple is not suitable for temperatures higher than 750°C due to iron being one of the conductors. Iron is also susceptible to rust.
- Another conductor, constantan, does not do well in oxidization, which makes Type J not suitable for harsh environments.
What Is Type J Thermocouple Used For?
- Vacuum applications
- To monitor the temperatures of inert materials that are not highly reactive, like sand, concrete, or asbestos-containing materials.
- Monitoring temperatures when manufacturing plastics and resins.
Type K Thermocouple vs. Type J Thermocouple: The Bottom Line
Type K thermocouple wire and Type J thermocouple wire are both versatile, reliable, and cheap types of thermocouples, but their applications do not overlap as often as you might think.
Use type K Thermocouple cable in high-temperature applications, corrosive environments, and applications where the cable is prone to oxidation. This includes damp applications and the ones that are submerged in water. Type J cable is your best bet in lower temperatures, as its temperature range starts at -40°C. It is also perfect for vacuum applications. In all other applications that do not specifically match these criteria, both Type K and Type J thermocouple wire can be used as long as their temperature range is met.
For thermocouple grade and thermocouple extension cables, visit Nassau National Cable.
