Types and Applications of Thermocouple
What is a Thermocouple?
A thermocouple is a temperature measuring sensor. Two different types of metal wires are connected at a junction which is called the thermal junction.
To measure temperature at any point, this thermal junction is subjected to that point which develops a thermal gradient or change in temperature at this junction.
The change in temperature at the junction creates a voltage used to calculate the temperature of the reference point using the reference tables.
Thermocouples are used widely across the different industrial and scientific applications.
Some of the most common application areas of thermocouples are;
– Industrial sectors
– Power generation
– Steel mills
– Oil & Gas Industry
Their cost-effectiveness, wide temperature range, and high durability make them a popular choice. –
To know about how thermocouple works, Click Here!
Two dissimilar metals used to create a thermocouple can be of varied types.
Different metals exhibit different properties, and the hot junction formed between these two metal wires defines the thermocouple.
To yield better results, scientists and researchers have standardized some metal combinations and segregated them as thermocouple types. Primarily there are eight types of thermocouples: B, E, J, N, K, R, T, and S type.
The alloy combination is of Platinum (6% Rhodium) and Platinum (30% Rhodium). This thermocouple exhibits a temperature range between 1370 to 1700 °C. It is mainly used in applications executed at extremely high temperatures, such as glass production. Click here for Data Sheet!
Chromel and Constantan are the alloys that form an E-type thermocouple. The temperature range is between 0 to 870 °C. This thermocouple does not focus on the oxidation in the atmosphere and can be used in an inert environment. However, they need to be protected against the sulfurous environment. They are commonly used in power plants. Click here for Data Sheet!
J type of thermocouple is formed with Iron and Constantan. 0 to 760 °C is its temperature range. Owing to the low-temperature range of the thermocouple, its life span reduces in high temperatures. J types thermocouple is best suited for vacuum and inert environment. Injection molding is one of the most common applications of such types of the thermocouple. Click here for Data Sheet!
Chromel and Alumel form a K-type thermocouple. The temperature range is between 95 and 1260 °C. The neutral or oxidizing environment is best suited for these types of the thermocouple. It generates an EMF variation below 1800°F due to hysteresis, which restricts its use in an inert and oxidizing environment below this temperature. They are most commonly used in refineries. Click here for Data Sheet!
This thermocouple is a combination of alloys Nicrosil and Nisil. The temperature range is between 650 to 1260 °C. Unlike K-type thermocouples, the N-type thermocouple offers very high resistance for degradation due to green rot and hysteresis. They are most commonly used in refineries and petrochemical industries. Click here for Data Sheet!
A combination of Platinum (13% Rhodium) and Platinum forms R type thermocouple. The temperature range is between 870 to 1450 °C. It is costlier than S type thermocouple as it contains a higher percentage of Rhodium. Its high accuracy and stability make it an ideal thermocouple to used in Sulfur recovery units. Click here for Data Sheet!
It is a combination of Platinum (10% Rhodium) and Platinum. The temperature range is between 980 to 1450 °C. S type thermocouple is used in applications involving very high temperatures. This type is widely used across various l industries. Click here for Data Sheet!
It is formed with Copper and Constantan. The temperature range is between -200 to 370°C. This type of thermocouple is suitable for the inert atmosphere as well as the vacuum. They are widely used as they generally resist decomposition even in a moist environment. They are commonly used in food production and cryogenics. Click here for Data Sheet!
RTD VS THERMOCOUPLE
Resistance temperature detector and thermocouple are both Temperature Measuring Instruments but are different in many ways.
A) Temperature measuring range: The RTDs have a low measuring range, whereas thermocouples can be used for high temperature, such as up to 1800°C.
B) Accuracy: RTDs are known to have relatively higher accuracy than a thermocouple at lower temperatures.
C) Sensitivity: RTDs are more sensitive and react faster to any temperature change than thermocouples due to the presence of cold junction compensation in thermocouples.
D) Drift: The design of the RTD sensor allows it to produce stable readings for a longer duration of time. RTD sensor drift is smaller when compared to Thermocouples.
E) Cost: RTD sensors are more expensive than thermocouples, but installation and maintenance expenditure on thermocouples can make them more costly in the long term.
To know about uses and types of RTDs, Click Here!
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