Temperature measurement has long been of interest to humans. Therefore, he invented various instruments such as thermometers, pyrometers, infrared and thermocouples. Given the breadth of this issue, in this article we have examined three questions. What is a thermocouple? What are the types of thermocouples? What is the use of thermocouples?
What is a thermocouple?
In fact, it is better to say that the thermocouple is a sensor or sensor for measuring temperature. In fact, thermocouples are a thermoelectric temperature detection sensor. These sensors have a simple internal system. Thermocouples are made of two heterogeneous wires. The two pieces are connected on one side. This is exactly where the temperature measurement connection takes place. The way thermocouples work is that when a temperature change occurs at the junction, a very small voltage difference occurs at the junction of the two wires, which is measured in millivolts. This voltage difference produces a potential difference due to the thermoelectric effect on the other two ends of the free, and since this difference is a function of temperature, the temperature can be calculated and the temperature can be measured using the thermocouple reference tables. One wire is a hot connection and the other is known as a cold connection.
What are the benefits of thermocouples?
The advantages of thermocouples include simple structure, low price, high durability, wide application and wide temperature range, as well as good resistance.
What are the disadvantages of thermocouples?
In addition to all the positive points of thermocouples, it must be acknowledged that these temperature measuring devices are not without flaws. The three major drawbacks of thermocouples are simply contact, moderate accuracy, which are not suitable for accurate measurements, and nonlinear temperature changes.
What are the types of thermocouples?
There are different types of thermocouples, each of which can measure a temperature range. This function is proportional to the type of wires and the thickness of the wires and other features of the thermocouple. Thermocouples are divided into 7 general categories, which are as follows:
• K series thermocouple:
This series measures temperatures between 0 and 1100 ° C. This series is the most widely used type of thermocouples. This series is made of metals such as nickel, chromium, aluminum, manganese and silicon. The two wires are made in such a way that the positive end of this type of thermocouple is composed of 90% nickel, 10% chromium and its negative end is composed of 95% nickel, 2% aluminum, 2% manganese and 1% silicon.
• J series thermocouple:
This series measures temperatures between 0 and 750 degrees Celsius. This series has a smaller range but is more accurate than its counterparts.
• N series thermocouple:
This series measures temperatures between 0 and 1100 ° C.
• R series thermocouple:
This series measures temperatures between 0 and 1600 ° C.
• S series thermocouple:
This series measures temperatures between 0 and 1600 ° C.
• T series thermocouple:
This series measures temperatures between -185 and 200 degrees Celsius. As you can see, the only series of thermocouples that can measure negative temperature and are unique in this respect are the T-series thermocouples.
• E series thermocouple:
This series measures temperatures between 0 and 800 degrees Celsius.
What is the use of thermocouples?
The use of thermocouples is abundant in many parts of the industry due to their many benefits. For example, thermocouples are present in all gas appliances and mainly in all gas industries and play a colorful role. The role of these thermocouples is more safety and they are used when the desired flame is extinguished and there is a gas leak, the thermocouples cut off the gas flow and prevent the release of gas.