Nicely and simply explained. For the sake of common sense, huge majority of the world and best engineering practices I hope you can refrain from using imperial units in the future
Principal mistake in the video is TC measures not temperature, but difference between temeperatures - between HOT and Cold (reference) junctions. each ITS table has note about, table works only when cold (reference) junction = 0 C Measuring device always add ambient temperature (temperature of cold junction) to result (converted from ITS). So, generally speaking - measurement system based on TC always measures two values - Voltage as function(Thot - Tcold) and ambient temperature. I think this is important note.
Hello Ave Vovus! Thank you for your comment! You are correct, and clearly know your way around a thermocouple! As a stand alone device, the voltage measured at the cold junction is indeed measuring the difference in temperature between the hot and cold junctions. As Surya Banyal points out, a more in depth discussion about cold junction compensation would help the more advanced users. The challenge with making a tutorial of this kind is about keeping things short and simple. Too much detail can dilute the core point of the discussion. In this case, it seems we didn't draw the line correctly for you and for Surya Banyal. For other users, an additional 5 minutes on cold junction compensation may have made the entire tutorial too long. Lesson planning is a balancing act. For the average industrial user, cold junction compensation is built into most reputable electronic displays and temperature transmitters, so a detailed understanding of cold junction compensation is not necessary...it just happens. For some brands of PLCs, however, if you are not careful and forget to order the cold junction compensation parts, you will get temperature readings that are somewhat flawed....which is the point of your comment. Thanks again for your comment! Discussions of this kind help round out the tutorials and create a better learning experience for everyone. Please consider checking out other RealPars videos!
Hey! But aren't the two metal wires also connected at the cold junction, and not only in the hot junction? Atleast in Uni teachers taught me like that. Thanks for the video!
Hi there, thank you for your question! Absolutely, your understanding is spot on, just as we mentioned in our video. To delve deeper into this topic, we recommend exploring information about the Seebeck effect. You can find valuable insights in the following link: en.wikipedia.org/wiki/Thermoelectric_effect Happy learning!
An excellent explanation, covering detailed concepts about thermocouples, even about the flow of electrons in the different types of metals connected at the hot and cold junctions of these temperature sensors, which are the most used among the others. Thanks no much RealPars.
Hi Deepak, Thanks for your comment! We currently only provide our course videos in English, you are always able to turn on the English subtitles as that might make it a bit easier for you. Our apologies for any inconvenience! Happy learning!
If I measure Micro voltage across the junction , it will be proportional to the temperature delta across two junctions. But in order to know the hot junction temperature I should know the cold junction temperature first on which temperature delta can be added to calculate hot junction temperature.So the problem is how to know the cold junction temperature?
For thermocouples, "cold junction compensation" takes the place of the lack of an ice bath reference at the cold end of the thermocouple. This compensation needs to determine the missing reference thermoelectric voltage since the thermocouple cold end of the thermocouple is not at (0°C /32°F). A very accurate RTD or thermistor is used to determine the actual temperature at the cold junction. The electronics in the transmitter then will add or subtract the reference temperature voltage from the measured voltage to compensate for the cold junction not being at 0°. The transmitter then uses the established thermoelectric voltage tables (or polynomials) to determine the temperature at the hot end.
@@stardust6457 Further to the answer above, some temperature transmitters are using precision semiconductor temperature sensing devices for Cold junction compensation.
