Instrumentation » Thermocouple

Thermocouple

Thermocouple is one of the common thermal sensors in various industries, which is sold at a more reasonable price than other temperature sensors in terms of performance and price in medium temperature ranges.

K and J type thermocouples are the most widely used types of thermocouples that come in a variety of shapes and dimensions for a variety of applications in industry over a wide range of temperatures.

What is a thermocouple? What are its types and applications?

Thermocouple is one of the most widely used temperature sensors. These simple sensors are produced using the connection of a metal and its alloy and according to the effect of the tuber, and with this simple mechanism, they are able to measure the temperature easily in a wide range from below zero to about 1700 degrees. With regard to the phenomenon of ball joint connection of both metals of different types creates a thermocouple and produces millivolt proportional to the temperature applied to so many different types of thermocouples can be produced while the common standards can be of 10 or 12 thermocouples to learn Which is produced in different models and with different shapes. Depending on the application, temperature measurement environment, temperature range, accurate measurement of thermocouple types can be referred to the following types:

(CHROMEL-ALUMEL) K-type thermocouple

Type K thermocouple is made of metal wire Ni-Cr (brand name Chromel) and Ni-Al (brand name Alumel). This thermocouple is inexpensive and is one of the most widely used thermocouples. Its operating temperature range is between −200 ° C and +1350 ° C and its sensitivity is approximately 41 µV / ° C and is usually used at high temperatures. K-type thermocouple has anti-oxidation properties due to the use of copper, so it is more suitable in furnaces where oxidation occurs.

(IRON-CONSTANTAN) Type J thermocouple

This thermocouple is made of Fe iron and Cu-Ni copper-nickel alloys. The temperature range of this thermocouple is between 80180 ° C and +750 ° C. Due to the possibility of iron oxidation, this thermocouple is used in the plastic molding industry. The sensitivity of type J thermocouples is 55 µV / ° C and is recommended for new designs. It is not used in type J thermocouples due to the presence of iron in places where oxidation is possible

(CHROMEL-CONSTANTAN) Type E thermocouple

Type E thermocouples are made using Ni-Cr (Cromel) and Cu-Ni (Constantan) metals. Its temperature operating range is between −40 ° C and +900 ° C. This thermocouple with 68 µV / ° C has the highest sensitivity and can be used in vacuum applications and in cases where the sensor is not protected.

(COPPE-CONSTANTAN) T-type thermocouple

T-type thermocouples are made of Cu copper and nickel-copper Cu-Ni alloy (Constantan). The temperature range of this type of thermocouple is between 50250 ° C and +400 ° C. This thermocouple is relatively inexpensive and suitable for low temperature applications and has good resistance to moisture. The sensitivity of this thermocouple is 46 µV / ° C. Type T thermocouple is used in the industry because it is more linear than all types of thermocouples and has a suitable temperature range and also has a good sensitivity.

(NICROSIL-NISIL) Type N thermocouple

Type N thermocouples are made of Ni-Cr-Si (brand name Nicrosil) and Ni-Si-Mg (brand name Nisil) metals. Its temperature range is between 70270 ° C and +1300 ° C. The sensitivity of this thermocouple is 30 µV / ° C and it is usually used at high temperatures.

(PLATINUM / 13% RHODIU-PLATINUM) R type thermocouple

(PLATINUM-PLATINUM / 10% RHODIUM) Type S thermocouple

(PLATINUM / 30% RHODIUM-PLATINUM / 6% RHODIUM) Type B thermocouple

Type B thermocouple, Type S thermocouple and Type R thermocouple which are made using Pt-Rh (platinum-radium) with different compounds. Their price is high and its sensitivity is very low and about 10 µV / ° C and its temperature range It is approximately +0 ° C and +1750 ° C. These types of thermocouples are used in high temperature measurements, for example in the glass and steel industry.

For comparison between different types of thermocouples, see the temperature range of different types of thermocouples and also the temperature tolerance of first class thermocouples in the following table:

Also, consider the class 2 temperature tolerance standard and some common standards for coloring wires of different types of thermocouples in the following thermocouple table: