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.
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.
Interesting. I thought the thermocouple current controlled a larger current via a transistor/relay. I didn’t realize it actually kept the solenoid open by itself.
@@sylviam6535 The reason they don't amplify the current with a transistor/relay is because this would require power. In the event of a power outage, this safety system would not work. By having the thermocouple current drive the gas valve solenoid directly results in a simple fail-safe system that doesn't rely on house power to operate.
ThermoPILES are used in that case, and they have like 11 or 22 thermocouples in series/parrellel wiring. The hot end sticks in the flame, and the cold end is 2 inches away near where the leads come out.
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"
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 !
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
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.
Even though this is a while ago mate, I wouldn't go for the Fluke brand... I have a MM 300 Kleins, (not the best) but also I have a DL479T (much better- has a clamp and many other uses 🦊for my HVAC-R equipment 🙂)
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.
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.
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.
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
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.
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".
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.
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.
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 ?
+lollandster ya, i sat there for a while trying to figure out why as the 2 temps come closer together, the volt difference diverged. glad to have this sanity check right below
I think so too. But what's the intention to go from 0 to 10 horizontally? I expect 0 to 9. Anyway, it's 1° step since the 10 values are equal to the next lines 0
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.
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. :-)
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 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.
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.
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.
+Neil Bradshaw i think you are almost right, not quite. he placed the iron on a junction of Cu-Cu. even if he placed it at 5% down, it's still Cu-Cu (less thermal mass on one side, so you would see more change). the junction needs to be 2 different metals for best results.
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.
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.
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 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.
Another application is in Radioisotope Thermoelectric Generators (RTGs) where thermocouples are used to convert the heat from a decaying isotope into electricity. Wiki RTG
did you read that Application Note you linked to, "Seebecks 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.
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.
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.
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.
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.
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.
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.
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.
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.
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).
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.
Hi Dave. I bought a Uni-T K/J type that came with two wires. Both have K Type embossed on the plug but they both have one red and one white cable. Are these K or J type thermocouples?
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
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 ?
Looks like you've misinterpreted calibration tables.Horizontal axis is just a least significant digit of temperature. Such form is used for compactness. Temperature value is a delta between cold junction and hot junction. Usually cold junction is held at 0 degrees during measurement of these tables.
If the thermocouple has to be compensated with a temperature sensor inside the meter, what is the temperature sensor's junction referenced to? Obviously, there cannot be an infinite number of junctions referenced to other junctions referenced to other junctions.
If you heat the centre of the yellow loop with the iron you'd expect very little potential difference between the meter cable ends, or am I missing something?
Question: Does the length matter??? I wanted to measure/calibrate my soldering iron temps. I was going to buy a 191 tool, but later thought getting a proper 2 channel device would have more uses. So, if I cut the leads down at the plug end of one of my probes, so I just have a little stub sticking out, that I can touch my hot soldering iron tip to, will it still read the same? Love all your videos, Thanks for sharing. I know this video is from 2013, hope you still check comments...
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?
Dave, what do you think of the cheap little yellow thermometers you can find on eBay by searching for "k type thermometer" and then sorting by Location > Australia Only? Do you think these would have features such as the thermal masses near the sockets like the Fluke one you showed in this video? Or would they just be useless crap?
At the hot end of the thermocouple, why is there always a blob of something? I understand that the manufacturer needs to attach the two materials together but the blob seems a little excessive and that blob can be coated in something. Why is this?
08Ultrasonic The blob is the welded junction,we made our thermocouples up by welding junction with acetylene torch,we ran temp.survey in hi temp.furnaces used for heat treating & annealing. The results were recorded on graph recorders for production tracking,also customer proof records. (It was thermo couple wire twisted at the end and then welded to form t.c. Hot junction)
Could someone tell me the best way to attach that point end of thermocouple to the measuring surface. It is so difficult to keep it in place without a fixture.
Just use some thermally conductive epoxy like Item# OB-100-1/4 from OMEGA. More importantly, to get an accurate reading the thermocouple should lay flat on the surface for roughly 10 x the wire diameter so that enough heat can be transferred into the thermocouple to balance the heat wicked away up the length of the thermocouple.
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.
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.
We use them and change them very often at work (for similar purposes you mentioned)...
@tzampini What sort of temperature difference would produce high enough current?
Interesting. I thought the thermocouple current controlled a larger current via a transistor/relay. I didn’t realize it actually kept the solenoid open by itself.
@@sylviam6535 The reason they don't amplify the current with a transistor/relay is because this would require power. In the event of a power outage, this safety system would not work. By having the thermocouple current drive the gas valve solenoid directly results in a simple fail-safe system that doesn't rely on house power to operate.
ThermoPILES are used in that case, and they have like 11 or 22 thermocouples in series/parrellel wiring. The hot end sticks in the flame, and the cold end is 2 inches away near where the leads come out.
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"
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.
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 !
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
Wow more involved than I expect rd this to be, thanks for taking the time to teach some of us, Dave
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.
Even though this is a while ago mate, I wouldn't go for the Fluke brand... I have a MM 300 Kleins, (not the best) but also I have a DL479T (much better- has a clamp and many other uses 🦊for my HVAC-R equipment 🙂)
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.
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.
Thanks a lot for your post. This is the most professional explanation about the work of thermocouple I could find on RUclips.. Great job!
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.
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
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.
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".
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.
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.
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 ?
That makes more sense, thanks for pointing it out.
I noticed that too. You have to be careful when listening to self-proclaimed experts, always check the source.
+lollandster
ya, i sat there for a while trying to figure out why as the 2 temps come closer together, the volt difference diverged. glad to have this sanity check right below
I thought so!!
I think so too. But what's the intention to go from 0 to 10 horizontally? I expect 0 to 9. Anyway, it's 1° step since the 10 values are equal to the next lines 0
Thank you so much for explaining all this.
Thx to who suggested to make a video about Thermocouplers and of course thank u Dayv
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.
Worth mentioning that the Curie Kink at about 300c was used to regulate early Weller soldering irons..
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. :-)
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 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.
I love the BTTF reference at 20:16!
Nice tutorial. Lots of "stuff" in there I've never thought about before! Thank's Dave. THUMBS UP!
Very clear and interesting, especially the temperature reference technique.
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.
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.
That was my impression also.
+Neil Bradshaw
i think you are almost right, not quite. he placed the iron on a junction of Cu-Cu. even if he placed it at 5% down, it's still Cu-Cu (less thermal mass on one side, so you would see more change). the junction needs to be 2 different metals for best results.
get a large bundle of thermocouples in an array and DIY your own thermal imaging :)
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.
Sometimes you are just amazing didactic, others, just brilliant.
Thanks Dave.
Hi there, from a fan in Dominican Republic!
Dave I always enjoy the tutorial videos.
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.
One of your best Dave, cheers.
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 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.
Another application is in Radioisotope Thermoelectric Generators (RTGs) where thermocouples are used to convert the heat from a decaying isotope into electricity. Wiki RTG
did you read that Application Note you linked to,
"Seebecks 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.
The reason they didn't solder it is you can't solder those metals. Ultrasonic welding is another option.
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.
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 like more videos like this, it was very educational.
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.
I would love to see one of those LASER Thermometers taken apart and explain how those work... they look like magic!!..
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.
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.
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.
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.
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.
Quiet a heap of info on TC's. Thank you
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).
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.
Hi Dave. I bought a Uni-T K/J type that came with two wires. Both have K Type embossed on the plug but they both have one red and one white cable. Are these K or J type thermocouples?
Anyway as usual, a very nice tutorial, learned something again today.
Thanks mate.
16:00 that is a very clever analysis
for the purpose of making a calibration of a thermocouple I want to know the existing methods of calibration please
thanks
Very informative. Was hoping you would to touch on PID control though
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
Back to the Future quote
Which one is the best multimeter for everything (professional, indesrtrial, home, electrical and electrician)
Great, love to hear the basics from you..
Everyone else is watching the Super Bowl. And I'm sitting here watching Dave Jones be AWESOME.
Great video Dave.
Very interesting indeed.
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 ?
Looks like you've misinterpreted calibration tables.Horizontal axis is just a least significant digit of temperature. Such form is used for compactness. Temperature value is a delta between cold junction and hot junction. Usually cold junction is held at 0 degrees during measurement of these tables.
Brilliant. You live and learn
Nice! I work with thermocuples and resistive sensor everydays!
If the thermocouple has to be compensated with a temperature sensor inside the meter, what is the temperature sensor's junction referenced to? Obviously, there cannot be an infinite number of junctions referenced to other junctions referenced to other junctions.
Look at peltier modules for that purpose.
Great video, I really like the tutorial videos.
If you heat the centre of the yellow loop with the iron you'd expect very little potential difference between the meter cable ends, or am I missing something?
Question: Does the length matter??? I wanted to measure/calibrate my soldering iron temps. I was going to buy a 191 tool, but later thought getting a proper 2 channel device would have more uses. So, if I cut the leads down at the plug end of one of my probes, so I just have a little stub sticking out, that I can touch my hot soldering iron tip to, will it still read the same? Love all your videos, Thanks for sharing. I know this video is from 2013, hope you still check comments...
Brilliant teaching. Excellent!
Finally some tutorials :)
Go on brother :)
Yes, you are right, oops. Will correct in annotation.
Awesome video!, thanks. 👍👍
WOW, its both, magic and complex ... how many coeff take the poly ?. Brilliant vid Dave.
Can i use these thermocouple to detect animals skin temperature? Thanks
Brilliant experiment, Thumb UPed already....
Would my Fluke 289 be as accurate at reading temperature with a K-type thermocouple as your CNX t3000 meter?
yes, is a reversible process
Very, very good video indeed - thx !
Can this be used to test circuit boards for showing, let's say and fuse or on board capacitor or small diod.
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?
Dave, what do you think of the cheap little yellow thermometers you can find on eBay by searching for "k type thermometer" and then sorting by Location > Australia Only?
Do you think these would have features such as the thermal masses near the sockets like the Fluke one you showed in this video? Or would they just be useless crap?
At the hot end of the thermocouple, why is there always a blob of something? I understand that the manufacturer needs to attach the two materials together but the blob seems a little excessive and that blob can be coated in something. Why is this?
08Ultrasonic The blob is the welded junction,we made our thermocouples up by welding junction with acetylene torch,we ran temp.survey in hi temp.furnaces used for heat treating & annealing. The results were recorded on graph recorders for production tracking,also customer proof records. (It was thermo couple wire twisted at the end and then welded to form t.c. Hot junction)
I love your channel thanks, could you discuss how strain gauges work and the method for reading the output? Thanks again
Does a peltier element also work like this?
I know you're an engineer Dave but how do you remember all that stuff? Percentages types of metals.....wow!
Great stuff, thanks!
No, they use water and steam turbines.
hey
nice tutorial, but i think you read the table wrong. the horizontal axis one degree increments and the vertical are ten degree steps.
what is used in high temp situations, like foundry or metal processing(2000c to 3000c)?
Great video, very helpful.
what type of metals did you use?
don't you need two types
Could someone tell me the best way to attach that point end of thermocouple to the measuring surface. It is so difficult to keep it in place without a fixture.
Just use some thermally conductive epoxy like Item# OB-100-1/4 from OMEGA. More importantly, to get an accurate reading the thermocouple should lay flat on the surface for roughly 10 x the wire diameter so that enough heat can be transferred into the thermocouple to balance the heat wicked away up the length of the thermocouple.
@@tomrestis4533 Very helpful. Thank you
Could you please make a basic SPI and I2C tutorial?