What is Thermocouple? Types of Thermocouples
Dear friends: Today, we will learn about a sensor that is used in both industry and our homes in this post.
You must be familiar with the term "thermocouple," which refers to a sensor that is commonly used in home appliances such as stoves, heaters, geysers, boilers, steam furnaces, etc.
We'll learn what a thermocouple is today in this article. types of thermocouples and their operational principles.
Therefore, let's clarify:
What is Thermocouple?
An electrical device frequently used to monitor temperature is a thermocouple.
Electrical junctions are made up of two separate conductors that come into touch with one another physically.
Typically, a thermocouple works by using the Seebeck effect. This action causes a thermocouple to produce a temperature-dependent voltage, which is then used to detect temperature.
Most temperature sensors utilise thermocouples to measure temperature.
The thermocouple is self-powered and more accurate than other temperature measuring techniques.
Since thermocouples have a system error of less than 1%, they are particularly useful in gas turbine exhaust, diesel engine exhaust, and other applications.
Principle of Thermocouple Operation:
The thermocouple's operating principle is primarily based on three effects:
- Seeback Effect
- Peltier Effect
- Thomson Effect
Seeback Effect
According to the Seebeck effect, an electromotive force (EMF) forms at two places when two electrically conducting materials have a temperature difference.
The Seebeck electromotive force is the name given to this electromotive force, and the Seeback coefficient is the measurement of the relationship between the electromotive force and the temperature difference between the two substances.
A thermocouple detects the potential difference between a hot end and a cold end for two distinct materials, with the potential difference being proportional to the temperature difference between the cold end and the hot end.
Peltier Effect
According to the Peltier effect, heat is generated at one junction and absorbed at the other junction when electricity flows through the circuit of a thermocouple.
This phenomenon states that any two dissimilar conductors can have their potential differences applied to them to produce a temperature difference.
Thomson Effect
The Thomson effect states that the temperature dependence of the Seeback coefficient in a different material is not constant. The material may cool or heat up if there is a temperature gradient running along it and a current passes through it.
Type of Thermocouples
Thermocouples typically come in three varieties:
A) Nickel Alloy Thermocouple
B) Platinum alloy thermocouples
C) Tungsten Alloy Thermocouples
A) Nickel Alloy Thermocouple
Generally speaking, there are six different categories here:
Type E (Chromel-Constantan) -
composed of constantan (an alloy containing copper 55% and nickel 55%) and chromal (10% chromium and 90% nickel) alloys.
It has a thermal sensitivity of up to (68 V/°C), is non-magnetic, and is suitable for cryogenic application.
wide range from -270 to +740 °C and
-110 °C to +140 °C is the restricted range.
Type J (Iron-Constantan) -
composed of alloys with a high heat sensitivity (up to 50 V/°C) made of iron.
40 to 750 °C temperature range
Type K (Chromel-Alumel) -
It is made of the alloys chromel and alumel, which are 95% nickel, 2% manganese, 2% aluminium, and 1% silicon.
This has a maximum thermal sensitivity of (41 V/°C).
between -200°C and +1350°C
Type M :
Its maximum operating temperature is 1400 °C, and vacuum furnaces are where it is most frequently utilised.
Type N (Nicrosil-Nisil) -
Nicrosil, a nickel alloy with chromium content of 14.4%, silicon content of 1.4%, and magnesium content of 0.1%, is manufactured from nisil, another nickel alloy with silicon and magnesium.
where thermal sensitivity can reach (39 V/°C).
250 to 650 °C about
Sort T (Copper-Constantan) -
A copper and constantan alloy with a thermal sensitivity of up to (43 V/°C) was used to make it.
200 to 350 °C in the range
B) Platinum alloy thermocouples
These thermocouples are exclusively used for measuring high temperatures since they are constructed of platinum, have a higher thermal sensitivity than conventional thermocouples, and are also pricey.
These mostly fall into three categories, which are as follows:
Type B: This thermocouple can withstand temperatures of 1800 °C.
Type R: Temperature range of 0 to 1600 Celsius.
Type S: 630 °C to 1064 °C in the range
C) Tungsten Alloy Thermocouples
The emission into the oxidising environment at high temperatures prevents it from being employed, despite its suitability for high temperature monitoring.
between 0 and 2315 °C
Conclusion:
What kind of thermocouple do we have today, friends? How many different kinds of thermocouples exist? and were aware of the thermocouple's mechanism of operation.
Please share with us any further questions or suggestions you may have regarding thermocouples.
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