While not being able to function at the most extreme temperature ranges, a K type thermocouple strikes a good balance between affordability and utility. Being capable of reading temperatures from -270 to 1260°C, it is possible to use it in a wide variety of different applications, from cryogenics to industrial metalwork.
However, since it is not tuned to a finer temperature range, it may not be ideal for highly specialized work. On the other hand, K types are considered reliable enough to be used in foodservice and even in hospitals. You will also often find them in boilers, oil heaters and engines.
The K type thermocouple probe is made of chromel and alumel. Alumel is a composite of silicon, manganese, aluminum and nickel, while chromel is composed of chrome and nickel. While inexpensive, a K type will still cost you more than a J type; however, the K type makes up for it by being able to read a wider temperature range than the J type thermocouple. Hi-Watt, Inc. carries a wide variety of thermocouple types as well as thermocouple wire, contact us for details.
K types are also more resistant to corrosion than the iron-containing J types. While thermocouples made of noble materials, such as the S, R or B types, do not experience aging of the emf characteristic as the K type does, the K type is touted as being the most stable among other thermocouples made of inexpensive materials.
While a B type thermocouple can withstand incredibly high temperatures, you must be willing to pay the price of the platinum if you choose to use one.
Keeping these features in mind, the question that arises is which sheathing composition, also known as a junction, is most optimal for the K type thermocouple.
If you are not working with any corrosive materials, you might find a benefit in using a bare wire junction. This simply means inserting the connected end into the process you need to read the temperature of, without any sheathing.
The primary advantage to this layout is that you will get the fastest response to changes in temperatures. However, it is often advised not to use this method as it is more likely for the wires to degrade through corrosion.
When you choose a sheathed junction, you have a decision to make as to whether to go grounded or ungrounded. An ungrounded thermocouple keeps the wires welded together while covering them with a sheath. There may be an added layer of insulation between the sheath and the wires to protect from electrical interference.
The feature that makes this junction ungrounded is that the wires never actually come into contact with the sheath. This layout may serve you better if you are concerned about electrical interference, but do not need fast response times.
On the other hand, a grounded junction acts for many users as a middle ground between an exposed and ungrounded layout. With this design, the wires and sheath are all welded together. The problem that some people run into with this layout is that it is susceptible to electrical interference. However, in certain environments, a faster response time is necessary, and that is made possible due to the ease of heat transfer from the sheath to the wires.
If you need a faster response time but are concerned about corrosion, a grounded thermocouple may be better suited for your situation.
We at Hi-Watt Inc. pride ourselves in providing quality temperature-reading devices for any kind of industrial application. We also offer the sensors required to provide accurate temperature readings, as well as bayonet adapters, compression fittings, connection heads, jack panels and connectors. If you would like to get a quote, call us today at 586-588-9479.