Checking thermocouple knowledge

In summary, thermocouples operate by utilizing two dissimilar metals at different temperatures to measure temperature. The introduction of copper into the mix can create additional EMF, which can affect the accuracy of temperature controllers. Compensating cables can be used to eliminate this issue.
  • #1
Micko
43
0
Hello to all.
I want to check my knowledge about theory nad principles of thermocoupels.
Please can you read .pdf file in attachment and comment?
Thank you very much in advance.
 

Attachments

  • Thermocouple theory.pdf
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  • #2
I wouldn't recommend Cu extension wires

Thermocouples work on the principle of having two dissimilar metals at unknown temperature (the measuring temperature) and at known temperature (the cold junction). By introducing copper into the mix, you are creating two additional junctions (for K-type thermocouples, you would have Cu/Ni-Al and Cu/Ni-Cu). These extra junctions introduce an additional EMF, unless they are held at 0ºC. Temperature controllers having built-in temperature compensation capabilities are not set up to correct for this additional EMF, as you mention. I would amend the following sentence, which refers to figure 1: "Here, compensation cables are not used and thus mV signal at controller end is proportional to (T1 - T2)." The mV signal measured at the controller will be the sum of a voltage that is proportional to (T1 - T2), and an additional voltage, which is proportional to (T2 - T3). The use of extension or compensating cables eliminates this additional voltage by using materials that are similar in the thermoelectric series to the thermocouple material.
 
Last edited:
  • #3


Hello there,

Thank you for reaching out and wanting to check your knowledge on thermocouples. It is always great to see individuals taking an active interest in their field of study.

I have reviewed the attached .pdf file and it seems to provide a thorough overview of the theory and principles of thermocouples. It covers topics such as the Seebeck effect, thermocouple materials, and the different types of thermocouples.

One suggestion I would make is to also explore the practical applications of thermocouples in various industries, as this can help solidify your understanding of their use and importance.

Overall, it seems like you have a good grasp on the basics of thermocouples. Keep up the good work and continue to expand your knowledge in this area.

Best of luck in your studies!
 

Related to Checking thermocouple knowledge

1. What is a thermocouple?

A thermocouple is a type of temperature sensor that consists of two different metal wires joined together at one end. It produces a voltage signal that changes with temperature, allowing for temperature measurement.

2. How does a thermocouple work?

A thermocouple works based on the principle of the Seebeck effect, where when two dissimilar metals are connected, a voltage is generated when there is a temperature difference between the two ends.

3. What are the common types of thermocouples?

The most commonly used thermocouples are Type K, Type J, Type T, Type E, and Type N. These types differ in terms of temperature range, accuracy, and application.

4. How do you check the accuracy of a thermocouple?

To check the accuracy of a thermocouple, you can use a known temperature source, such as a thermometer or a calibrated temperature bath, and compare the readings with those of the thermocouple. You can also use a multimeter to measure the voltage output of the thermocouple at different temperatures.

5. What are the common sources of error when using a thermocouple?

The common sources of error when using a thermocouple include electromagnetic interference, temperature gradients, and thermal shock. It is important to properly shield the thermocouple, minimize temperature differences along the wires, and avoid sudden changes in temperature to ensure accurate readings.

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