The most commonly used thermocouple type has a grounded construction, chosen primarily for their speed since they are 50% faster than ungrounded types. Their two wires are welded to the side of the metal probe sheath with the tip of the probe completing the circuit.

The least used thermocouple is the exposed type where the thermocouple sticks out of the sheath and is exposed to the environment. It has the highest response time but is limited to applications that are dry, non-corrosive, and non-pressurized. Since the element is exposed, it is subject to damage and corrosion.

Type C thermocouples are made of tungsten and rhenium. They are used in applications that produce high temperatures up to 4200 degree F or 2315 degree . Type C thermocouples are used in hydrogen, inert, or vacuum atmospheres to prevent failure from oxidation. They have protective sheaths made of molybdenum, tantalum, and inconel with insulators made of alumina, hafina, and magnesium oxide.

Type E thermocouples have chromel, a nickel and chromium alloy as positive legs and constantan as the negative leg. They have a temperature range of {{0}} degree F to 1600 degree F (0 degree to 870 degree ) with excellent EMF versus temperature values. Type E can be used in sub-zero temperatures and have colorings of red or purple. They can be used in inert environments but must be protected in sulfurous environments.

Type J thermocouples have iron for the positive leg and constantan as the negative one. They are used in oxidizing, vacuum, inert, and reducing atmospheres with injection molding being their most common application. Type J thermocouples have to be closely monitored since the iron leg can rust. Their temperature range is 32 degree F to 100 degree F (0 degree to 760 degree ) and have a red or white color. The lifespan of a J type thermocouple can be when they are continually exposed to high temperatures.

Type K thermocouples have chromel for the positive leg and alumel for the negative leg. Alumel is an alloy made of mostly nickel with low percentages of aluminum, silicon, and manganese. Type K thermocouples are used in inert or oxidizing environments with a temperature range of -300 degree F to 2300 degree F (650 degree to 1260 degree ). They generate an EMF variation in temperatures below 1800 degree F (982 degree ), which limits their use in inert environments. . Their color coding is red or yellow.

Type N thermocouples have nicrosil, a nickel chromium alloy, as the positive leg and nisil, a nickel, silicon, and magnesium alloy, as the negative leg. They have a temperature range 32 degree F to 2300 degree F (650 degree to 1260 degree ) with color coding of red or orange. Type N thermocouples have exceptional resistance to green rot and hysteresis and are used in refineries and the petrochemical industry.

Type T thermocouples have copper as the positive leg and constantan as the negative one with a temperature range of -330 degree F to 700 degree F (-200 degree to 370 degree ) and color coding of red or blue. They are ideal for inert atmospheres and are resistant to decomposition. Type T thermocouples are used in food production and cryogenics.

The Type B thermocouple is used in extremely high temperature applications and has the highest temperature limit of all of the thermocouples with exceptional accuracy and stability. Its alloy combination is Platinum (6% Rhodium) and Platinum (30% Rhodium) with a temperature range of 2500 degree F to 3100 degree F (1370oC to 1700 degree ).

Type R thermocouples have platinum with 13% rhodium and platinum legs with a temperature range of -58 degree F to 2700 degree F (870 degree to 1450 degree ). They are more expensive than S type thermocouples due to their high percentage of rhodium. Type R thermocouples have excellent accuracy and are used for sulfur recovery. They provide the same performance as Type S and can be used for low temperature applications because of their stability.

Type S thermocouples are used in high temperature applications in the BioTech and Pharmaceutical industries. They are also used for low temperature applications due to their accuracy and stability. Type S thermocouples have a temperature range of -58 degree F to 2700 degree F (980 degree to 1450 degree ).

The Type P has the same curve at high temperatures as Type K and can be used in oxidizing atmospheres with a temperature range up to 2300 degree F. A Type K extension wire is used to connect a Type P thermocouple to the measuring instrument.