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Hi Dave - very helpful. BTW you misunderstood the NIST table. Everything in the whole table is referenced to 0 degrees C. The 0-10 columns just give you the last digit of the temp in degrees C. For example if you want to know the mV value corresponding to 1005 degrees, go to the 1000 row and look under column 5.

Amazing, I simply became captivated when you performed your Seebeck experiment with the looped wire. These kinds of things are really what sets apart "just a tutorial" from "an explanation"

Thanks a lot for your post. This is the most professional explanation about the work of thermocouple I could find on RU-vid.. Great job!

Great Tutorial. Very good explained. The great thing about you dude is you opened up your instrument for viewers to increase our knowledge. That's the great Seebeck Effect we got :-) . Thanku !

Wow more involved than I expect rd this to be, thanks for taking the time to teach some of us, Dave

Brillant! This video and the tear down of the fluke before it are just excellent. I love how this video tied in the mechanics (iso thermal block) of the tear down. Really love this style or combination of videos. I've got a EE degree and been in the buisiness (mostly software side of things) for around 18 years and your knowledge of the subject is expert and your ability to present it in easy to follow format is brilliant. Topics I've not seen since my college days are coming back to me

An interesting thing about thermocouples that many may not realize is that although they generate a relatively small voltage, they can generate a high current if their load resistance is low, and the temperature differential is high. The current can be more than half an amp, maybe up to an amp or more. An example of this is a furnace that uses a thermocouple to monitor the gas pilot flame. In this application, it must generate enough current to hold a solenoid open to allow gas flow.

Dave, thanks, I have pondered ocer this cold junction comp for about 3 months now, I didn't have the time to figure it all out myself. You cleared it all up in 30 minutes. These type of dare I say it "educational" videos is where you excel, clear concise and maybe the odd mistake but hey, they happen and people should take it on the chin. Thanks again

Nice tutorial. Lots of "stuff" in there I've never thought about before! Thank's Dave. THUMBS UP!

Thx to who suggested to make a video about Thermocouplers and of course thank u Dayv

Sometimes you are just amazing didactic, others, just brilliant. Thanks Dave.

Dave I always enjoy the tutorial videos.

Very clear and interesting, especially the temperature reference technique.

Thanks Dave, I love videos like this! They provide a practical insight on things you hear people talk about a lot, but you might be uncomfortable with asking how they work because you don't want to look like a berk. I really enjoy videos where you share insight and experience, they're inspiring and I've learned a lot from them (for instance, I now have screw-you money stashed). I'd love to see more like this.

Great, love to hear the basics from you..

One of your best Dave, cheers.

In the new videos about thermocouples with multimeters, you mentioned this old one - great and informative as usual. However I think I found a flaw at around 12:01 Minutes when you explain the NIST K-Type table.. I think it’s not cold on the X-axis and hot on the Y-axis. It’s a linear list from -270 - 0 °C in one degree steps. If you want to know the value for -13°C , you go the „-10“ line in the „-3“ column and get the value of -0.508 for -13°C.

The Seebeck effect does apply to a single wire, and that is precisely why thermocouples work. A thermocouple is two different metals with two different seebeck effects. It's just that a single wire seebeck effect is not practical, but it does actually exist. See the link in the video description.

No doubt, Mr. Jones is god. I could sit 24/7 and watch this man but I've got my own miracles to pull. Thanks for the videos, Mr. Jones.

Brilliant teaching. Excellent!

Anyway as usual, a very nice tutorial, learned something again today. Thanks mate.

The seebeck effect does happen on a single conductor, it's just not called a thermocouple in this case. A thermocouple by definition uses two dissimilar junctions.

I would like more videos like this, it was very educational.

Quiet a heap of info on TC's. Thank you

Great video Dave. Very interesting indeed.

Hi The bit about the compensation table is wrong. The scale along the bottom is just to provide the 1 Deg. steps. The vertical scale goes up in 10 deg. steps so you go the the 10 deg step that is lower than the temperature that your cold junction is at and the use the horizontal table for the 1deg finer steps. OK ?

Back to the Future quote

Great video, I really like the tutorial videos.

I've read about this effect in a physics book, and it says that of course you will get a voltage across the wire if you are using just one metal, but it will be an inner field, which you can't measure from outside with a probe. So if you are using just one wire and getting a voltage reading, it will be due to other materials (metals) in your measuring circuit. Thats why you have to have the other metal with, of course, a different seebeck coefficient, to not zero out the voltage drop.

Finally some tutorials :) Go on brother :)

In theory, yes, it should cancel out, as it's effectively a thermocouple with two identical metals with identical seebeck coefficients. In practice, it can produce a small dynamic effect like you saw. You may have noticed it actually started going back down the longer the iron was on there.

I love the BTTF reference at 20:16!

Have watched a lot of videos on TC's and the people making a big deal about the bead on the business end of the TC wire. They go to great extents to make sure there are those same two types of wires through the entire length from the tip back to the meter. All you really need to care about is making only one transition. When I worked for a US defense contractor in the 80's, I used to make thermocouples for the various temp tests from TC wire on spools of wire. I would cut off 10' of wire, strip and twist one end, and give it a blob of solder, then run the wire back to the patch panel, which was all standard nickle plated bus bars. No need for all the fancy plugs, extension cables, etc. Can use a 16 AWG extension cord if you need to. Besides, what you connect that TC to will not be made of the dissimilar metals.

Funny that I keep coming across thermocouple stuff right now that it's relevant to my interests... I've been looking at making a reflow oven and am collecting parts at the moment.

Extremely informative, Thanks!

Brilliant. You live and learn

Great video, very helpful.

Thanks so much Dave - Part of my job is validation of thermal processing of foods using T-type thermocoupes inside what is effectively a giant pressure cooker. I had some understanding of all of this, but your concise explanation cleared some concepts up and added a couple more. It's always easier to troubleshoot problems when you have some background right? Keep up the good work mate, love your videos.

Note that in order to have seebeck effects you must have TWO types of metals and they MUST be of different types, one should be p-type and the other n-type. The electrons' flow from the n-type to the p-type is possible because the p-type material has holes, which are positively charged spaces.

Yes, it's all related the thermoelectric effect. There is the "seebeck effect and the "peltier effect", sometimes joined and called the "peltier-seebeck effect".

Very, very good video indeed - thx !

Worth mentioning that the Curie Kink at about 300c was used to regulate early Weller soldering irons..

Hi there, from a fan in Dominican Republic!

Awesome video!, thanks. 👍👍

Great stuff, thanks!

Nice! I work with thermocuples and resistive sensor everydays!

Good tutorial. Note: only some thermocouples work direct in liquids, like PVC or waterproof types, some soak up liquids and affect the result. Just a tip, use non-conductive fluids with TC's in a tube an immerse it into the liquids with the reference probe, keep in mind temperature ratings on all devices used.

thanks for this lesson

Thanks Dave ! very interesting

Brilliant experiment, Thumb UPed already....

You surprised me a lot!! When you had that cobber cable in the multimeter, I did think that it will never work! Seebeck's first rule was "Two like metals won't work" or something like that. :-)

Yup lol i love all his other vidoes and i find them quite informative..... and i must congratulate Dave on his other videos as i have prob spend alot of time watching most of them and learning alot along the way....... the copper wire and to soldering iron was just proving that the wire he was using had some small inhomogeneities in the wire...... Its was nice to see the ITS90 polynomial coefficients as i had to type all those into excel macros :).... Thank you for the video :) Dave

16:00 that is a very clever analysis

Very informative. Was hoping you would to touch on PID control though

There is also a thermo couple that is copper filled with mercury that is used in water heaters and old floor furnaces. They actually mechanically push valves with the pressure created by the expansion of the mercury. Kinda confusing me by the use of the name over and over. But in these types the resistance change in the wire caused by the heat don't play a factor in the measurement? Thanks for the video, I always find them very enlightening. Well done as always.

At the begining of the video I think the demonstration of the seebeck effect with its explanations could be wrong. The soldering iron was placed near centre of the wire and the only reason for the voltage going up was because the soldering iron was not dead centre. I bet if the iron was place 30% of the way along the wire where the conducted heat would not really heat the banana jack the voltage output would be higher than in your example.

Awesome :). Thank you

I love your channel thanks, could you discuss how strain gauges work and the method for reading the output? Thanks again

great video great experiment！

get a large bundle of thermocouples in an array and DIY your own thermal imaging :)

Awesome :) Thanks Dave :)

The reason they didn't solder it is you can't solder those metals. Ultrasonic welding is another option.

Another application is in Radioisotope Thermoelectric Generators (RTGs) where thermocouples are used to convert the heat from a decaying isotope into electricity. Wiki RTG

I believe that another reason for the cold junction to have a high thermal mass is to limit the rate of change of temperature when the ambient temperature does change, so that the sensor that is measuring the cold junction can keep up with the rate of change. This brings me to another advantage of thermocouples - rapid response to temperature changes.

I did an essay for the IB at school on thermocouples. Ice and water on one side and different really hot stuff on the other. Crazy for my school poor man's lab.

I would love to see one of those LASER Thermometers taken apart and explain how those work... they look like magic!!..

Nicely explained but there is an error there, I think, about the NIST chart. I believe that the horizontal line is actually the subdivision of temperature rather than the cold junction temperature. You can easily confirm that by checking that the last column value is identical to the first column of the previous row when negative and the to the next row when positive.

Yes, you are right, oops. Will correct in annotation.

also resistive welding works well too. there are a few web pages where people have home made spot welders. For small stuff, not the automotive type There are spot welders made for jewellery work that can spot weld thermocouple wire together.

Thanks

If you want to produce some usable power get a peltier block and heat up one side while keeping the other cold. You can actually get enough power to light up small lamps and stuff.

This was a beautiful demonstration of thermocouples and their physics. I feel however, RTDs, are the industry standard for high precision temperature measurements. I'm somewhat surprised that thermocouples are used so much when keeping track of junction temperatures and metal composition is such a pain in the ass in comparision. I suppose cost (which have dropped in RTDs recently) of the element is driving it, but it seems the effort in "reading" a thermocouple is much more complicated.

well, yes the effect don't go away, but your measuring at the end of a conductor, the temperature along the conductor don't matter, if it did the whole idea of the thermocouple would not work. but your right that it is good to know of the effect, as smd resistors also has dissimilar junctions, and and a small temperature difference from one end too the other, can give an error if you are working with precision electronics.

So nice ... +1 fan from brazil =D

did you read that Application Note you linked to, "Seebeck’s experimental work showed that if a voltmeter circuit wiring and the conductor under test were both the same material, then the net loop voltage is zero because [Sa*(T1-T2)+Sa*(T2-T1)=0]." Yes the effect is there in a single wire, but you can't measure it because either your probes are the same material as the wire, and cancel the effect out, or a different material and then they are the second material wire.

seems 4 viewers of the video forgot their monitor and speakers turned off while trying too watch the video. anyway, If you want a cheap multimeter with no built in thermal sensor but comes with a thermocouple, check out the craftsman 82345 multimeter (I think it just assumes that the ambient temperature is at 70F (21.11C) (purchased it for $15 a few years ago mainly to use as a battery tester, especially for the cordless drill which which does not have any overcharge protection).

And also the voltage you will get will be very small, because the types of juncions normalized were choosen because they produce the biggest thermoelectric voltage compared to other junctions. The bigger the voltage you get, the bigger the precision you get.

Yes, but both alligator-metal junctions will be at the same temperature (ambient temperature) so you won´t get any voltage. You need two junctions at diferent temperatures. If you put one alligator-metal junction at ambient temperature and the other at the temperature you want to measure, you will have a thermoelectric voltage, but you won´t know what temperature correspond to that voltage, because for that junciont you have not tables. The types of junctions are normalized.

Back in the day we actually had ice bath units as the cold junction reference. As I recall the bath was controlled by monitoring the volume of ice water so that the system was maintained with some ice and some water. If it was allowed to get colder the volume would increase as more water turned to ice so by making sure the volume didn't increase or decrease beyond certain limits then you knew there was a solution with ice and water so you could know for sure you were at zero Celsius.

tks

Look at peltier modules for that purpose.

yes, is a reversible process

WOW, its both, magic and complex ... how many coeff take the poly ?. Brilliant vid Dave.

The cool thing is that this Peltier-Seebeck effect is reversible !! Like in Peltier cells, by powering the Thermocouples, you get a Heat Pump !! In fact, Peltier Cells are many Thermocouples joined together.

I know you're an engineer Dave but how do you remember all that stuff? Percentages types of metals.....wow!

Great video! Im thinking about making ultimate DMM(measuring everything, from standard volts to radiation) in far future and that was helpfull!

No, they use water and steam turbines.

Could you please make a basic SPI and I2C tutorial?

The space probes use the Peltier effect

according to RU-vid, one thermocouple generates 0.05 volts so 60 connected in series and placed in the freezer might light an l.e.d 🧊🤔😃🙇‍♂️

20:16 Back to the Future reference!

Yep got pne pf thoes on top of a wood burning stove running a fan.

When you used the soldering iron to heat the centre of the wire I expected the meter to show no change. Does the effect of the temperature differential between the centre of the wire and each end not cancel out ?

I wonder how Thermoworks are getting an accuracy of +/- 0.4 deg C with their Thermapen, which uses a K-type TC? Are they calibrating each device carefully, to characterise the individual sensor in each unit? How much error is random, and how much can be calibrated out?

hi david. nice tuts! how about a tutorial series of how to assembly an android tablet from scratch?

Is there a shortest wire consideration for building a K type thermocouple? In my application I need 20cm probe lenght at most. Temperature to measure up to 250 max, mostly 220-230 range. I figure out that silver solder works good for hot juncture.

I know! when i made my reflow oven controller i tried to solder to cromel for like 5 minutes! Doh!

Everyone else is watching the Super Bowl. And I'm sitting here watching Dave Jones be AWESOME.

The temperature probe for my oven broke, and they want $100 for a replacement. Knowing what's in it I just can't bring myself to buy a new one. It's probably 15 cent if I could just find the Chinese factory....

At the 6:15 mark I made a copy of Dave's fingerprints!