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Thermocouple vs. Thermistor[edit]

The explanation of cold junction compensation says you need a secondary thermistor to correct errors in thermocouple reading. This begs the question, "why not just use a themistor?". I assume the answer has to do with dynamic range (and maybe precision, although the article says thermocouples are difficult to get better than 1 degree celsius resolution...). But it would be nice if there were some explanation in the article. --User:Chinasaur

The primary reason is "dynamic range" (a good thermistor usually has a narrow temperature range), with other reasons being self-heating (unlike a thermocouple, you have to apply current to it) and the very non-linear resistance vs. temperature curve. Hmmm, the real way to answer this is with the various electronic temperature measurement pages having the pros and cons of each style of device. I'll put that on my (long) todo list. -- Kaszeta 20:04, 5 Oct 2004 (UTC)
How would you program the Voltage-Tempature relationship? 02:51, 6 September 2006 (UTC)t59
From my experience and experiments a thermocouple has a much greater accuracy than +/- 1K. Oystsot (talk) —Preceding undated comment added 17:22, 7 August 2009 (UTC).

Deleted 'Dawson' Theory[edit]

deleted the following:

"Recently discovered by MA Stephen Dawson, thermocouples may be used in conjunction to calculate circuit Q factors as well as measure Impedance. (XL, XC): The formulas: 2π x F x L OR 1 / (2π x F x C) may be used to calculate such things. Stephen Dawson's discovery states that these can be calculated by a thermocouple device, to gain accurate results an orifice plate may be used within a DP Cell. "

As written, it conveys no useful information, and makes confusing assertions without references, and sounds moreover like self-advertising. There may be a relation between thermocouples and electrical circuit Q, but none that I can find in any textbook, and none that I have encountered in a decade of working with thermocouples.

Sounds good. I don't even understand what they're implying, now that I think of it. Maybe using thermocouples inside an oscillator or something? - Omegatron 18:09, Apr 4, 2005 (UTC)

The above is very much nonsense. The formulas listed are just the basic first year formulas for capacitive and inductive impedance. An orifice plate withing a DP cell? Okay for starters a DP cell is about the size of a quarter is a piezoelectric or capcitive sensor about 5mm thick and an orifice plate is a big, heavy, steel plate used in industrial pipe-works to set up differential pressures in flowing fluids to measure flow rates. -Jim Eld

Two junctions[edit]

Why are two juctions needed, as I currently understand it one juction will produce a EMF, so why are two juctions needed? mickpc

Without a second junction, how could the electric circuit ever be closed? Think about it: We have the voltage generated at the (hot) junction between, say, the copper and iron wires, but now those electrons have to get back home. Somewhere, there must be a second place where the copper and iron touch (well, unless you're simply measuring the electrostatic field that is generated).
Atlant 12:19, 2 August 2005 (UTC)

Ok, well technically you can simply use the perant metal as a wire so u can use one junction. But my question revolves around; if the actual junction causes the EMF or the perant metal does, reading the article again I am tending to think that the EMF is devolped across the perant metal. mickpc

I think you need to draw yourself a diagram. Draw the iron wire. Draw the copper wire. Connect them at one end of your diagram to create the hot-side thermocouple. Now figure out how you connect the wires at the other side of your diagram to create a complete circuit.
Atlant 11:09, 3 August 2005 (UTC)

I asked my lecturer and he said that only one junction is needed and this is generated from the junction itself, now either he is wrong or the article is wrong (and I doubt he is entirly wrong) mickpc

Like I said, you figure out how to get the electrons back around the circuit without another metal-metal junction and you post it here.
Atlant 23:20, 21 August 2005 (UTC)

Quite simply, just use the parent metal as the lead wire (or use a lead that is the same composition as the perant metal). This is tyically done to extend the distance between the two junctions or to the output transducer. mickpc

I'm having trouble understanding why you don't get this. Draw the picture! Assuming you have an actual circuit (a "circle"), you are *ASSURED* of having at least two junctions (where A meets B and then where B meets back up with A), and if you have binding posts and other hardware in the circuit, you may have far more than just two junctions.
Atlant 23:28, 27 August 2005 (UTC)

Please dont get me wrong here, I am only trying to clarify (deepen) my understanding, so I am open to constructive critsisim. You can have a single junction for a thermocouple, just use two dissimlar metals (wires) and join them at the junction. This will produce an EMF. Why you typically use a reference junction I am not entirly sure on, I am thinking that it is most likely the linearisation and stabilty. mickpc

Great; you've got an EMF, but what will you *DO* with it? Unless you have an electrometer handy, there's no way to read that EMF that doesn't draw at least a little DC current from the thermocouple. And the moment you start to draw DC current, you have to close the circuit. And then you're back to the problem I've been trying to raise to your attention: a complete circuit must have at least two junctions.
Atlant 12:11, 30 August 2005 (UTC)

Point taken, well I should have thought more about the this before hand, I read that the voltages are produced at the junctions but the article Peltier-Seebeck effect it is said that it is due to the diffusion mickpc

Just wanted to point out (as my physics mentor told me long ago) that there are always at least 2 junctions in a thermocouple sense circuit. The other junction, is created when the thermocouple is connected to the EMF sense device (ie the thermocouple meter, or sensing circuitry). The volt meter probes will create the other junctions when one connects the iron-copper wires to read the TC junction voltage.

The Seebeck effect causes a voltage to form that is proportional to the difference between the temperatures at the two respective junctions. You need to complete the circuit. Your hot junction is the measurement point, the cold is your tranducer (right at the terminal, unless youve got a nice TC input card.) Jim Eld —Preceding unsigned comment added by (talk) 04:26, 18 April 2009 (UTC)

To clarify for mickpc or others, any modern thermocouple measurement runs the thermocouple leads to a DC pre-amplifier, to magnify the very small voltage about 100 times. Because after it's magnified, the thermocouple part of the circuit is pretty much done and the rest of the circuit doesn't have to worry about screwing up the measurement. Well, any microvolt DC preamp starts with two metal input leads of the same metal; you may assume it's copper. They actually do use the same metal; it's very difficult for the preamp chip maker to guarantee low temperature coefficient of input offset (also called drift, specified in uV/degC) without carefully avoiding different metals in the input leads, because those would act as unintentional thermocouples. So, in our thought-expt., preamp-neg-copper connects to thermocouple-neg-copper (same metal, so not a thermocouple junction) and thermocouple-pos-iron connects to preamp-pos-copper, which is the 2nd junction, and it better be at room temperature. Then out in the measuring tip, thermocouple-pos-iron is joined directly to thermocouple-neg-copper, and this is the 1st junction. That makes it a closed loop circuit, for which the loop-integral of thermal emf is well defined. True the preamp does have sort of an open-circuit inside, but really it's within one silicon chip where the voltage difference is being counted up carefully. More appropriate to think of it as a capacitor that measures it's charge, than an open circuit. jimswen (talk) 22:33, 23 August 2009 (UTC)

Re: Compensating/Extension cables[edit]

I agree of course, but was just trying to keep it a bit simpler. However, I have re-added the bit about adding the compensating voltage to the thermocouple voltage to get accurate result. Dave 21:59, 24 March 2006 (UTC)

Other kinds of thermocouples?[edit]

In a book by Patrick Moore thermocouples is said to be used to measure temperatures at Venus before the space age. This makes no sense to me as thermocouples are used in situ. Can anyone explain how thermocouples work in this case? Gunnar Larsson 20:12, 25 March 2006 (UTC)

I'm not an astronomer but I suspect the instrument used to measure Venus's temperature was a bolometer which is a specialized form of radiation thermometer that converts infrared energy into a tiny temperature rise, which then warms a thermocouple. So, it is an indirect use of the thermocouple principle. ( And now Wikipedia has got to the point where if you just blindly link a technical term like bolometer, chances are very good you come up with a blue link not a red link!) --Wtshymanski 17:26, 26 March 2006 (UTC)
That sounds exactly right; I couldn't remember the term last night.
Atlant 21:19, 26 March 2006 (UTC)
Ah, this makes more sense to me. Thanks! :-) Gunnar Larsson 18:40, 27 March 2006 (UTC)

Would it be possible to also mention the properties of type D and G thermocouples? H rossouw (talk) 08:45, 5 March 2009 (UTC)


A bit more information about thermopiles would be appreciated as I was redirected here from "thermopile". My understanding is that a thermopile is a number of "stacked" thermocouples to generate useful amount of power, where as a thermocouple can only output enough power to be useful as a sensor. I have no references for this piece of information other than sales information from an unvented propane heater.

Great listing of thermocouple types. Thanks. John H.

I use thermopiles on a daily basis to measure the power of laser beams. I added a section about this. I assume that the function in the propane heater is similar to that in heating appliances: the thermocurrent is used to keep a valve open. Putting several thermocouples in series increases the voltage. Han-Kwang 23:05, 7 July 2006 (UTC)
Right, but lots of convection heaters also use the thermopile voltage (through the thermostat) to also operate the main gas valve; the article discusses this.
Atlant 23:25, 7 July 2006 (UTC)
Yes, I can imagine so if it has to regulate a thermostat, but you have modified the section about guard flames. Search the net for "guard flame thermocouple millivolt" and you'll see plenty of service instructions explaining that its voltage should be in the 10--30 mV range, which corresponds to 200-600 K temperature difference over a single thermocouple. You don't need much to power a solenoid that is just there to keep a spring-loaded valve in the open position. Han-Kwang 11:02, 8 July 2006 (UTC)

This article is terrible, and has many errors, both technical and grammatical. For example, the list of coefficients for a K-type starts with n=0, which means a temperature difference with no voltage difference. And heat and temperature are confused. I could go on and on. Someone should start from scratch instead of trying to edit this.

Hal Lewis —Preceding unsigned comment added by Hallewis (talkcontribs) 19:49, 2 March 2009 (UTC)

Hi, wikipedia noob here so I don't know the protocols. Thermopiles are often used in industry to either increase the °K to mV gain of the sensor when stacked in series, or they are stacked in parallel in order to build in redundancy. They are cheap so it's better to just install 10 in parallel then send one of your guys out to repair it 9 times. -Jim Eld

Incorrect info[edit]

I believe that the included coefficients for Type K thermocouple aren't correct. There is no way that the coefficients of larger powers should get exponentially bigger.

 —Preceding unsigned comment added by (talk) 19:18, 10 March 2009 (UTC) 

Just say me wether the area of contact of the two metals do depend on the Volt per degree Centigrate. if not so then parellel connection should not have any variation in its output, but here it does showes variation. Why? and Why? —Preceding unsigned comment added by (talk) 13:41, 30 March 2009 (UTC)

Different issue: The "(nic-iron)" after Type N doesn't sound correct to me. It's at least not as descriptive as the others. Type N uses Ni/Cr/Si vs Ni/?/Si, with the Si there mainly to make protective surface oxidation for high temperature use. I forget what the "?" trace metal is; it may not be very important to the EMF. Even if it is Fe, maybe the description should read ("nic-iron") to show it's referring to a type-name, not to a pair of specific metals. jimswen (talk) 22:50, 23 August 2009 (UTC)

Curie temperature of iron[edit]

The number appears to be wrong. Please see discussion here:

Guy Macon 09:59, 15 July 2010 (UTC)

Followup: User Wtshymanski corrected it here and on the curie temperature page. —Preceding unsigned comment added by Guymacon (talkcontribs) 15:54, 15 July 2010 (UTC)


I noticed the thermoelectric effect navbox template has been moved to the very bottom of the article. This template is meant to be used on the side (unlike some others, see for example the bottom of states of matter. Incidentally, the other links in the navbox should show it being used as intended. I will put it back to the side but I just wanted to check here beforehand in case anyone had any concerns. Thanks, David Hollman (Talk) 10:39, 31 August 2010 (UTC)

Like most navboxes, it's a giant distraction at the top of the article. Do we need it at all? Wouldn't a few in-text links and carefully-chosen entries in "See Also" do a lot more for explaining the topic, instead of a loose collection of facts jammed willy-nilly into a navbox? Please don't put it at the top of the article, the picture isn't even relevant to thermocouples. --Wtshymanski (talk) 12:59, 31 August 2010 (UTC)
I would concur with that in the majority of cases. Kbrose (talk) 03:37, 16 September 2010 (UTC)
From my own experience, when I am not very familiar with a topic a good navbox not only provides links but also structure, which I find very useful. Another advantage is that as the template evolves all the articles benefit, rather than having to keep lots of "see also" sections updated. (Actually, this page [1] explains the benefits pretty well. Also note the mentioned study). However I do appreciate the "clutter" concern... In some articles navboxes are placed in an "introduction" section instead of at the very top, which seems to work okay; this article doesn't have a real "introduction" but given the content of the navbox the "principle of operation" section might make sense. What do you think about putting it there?
In any case I will remove the navbox from the very bottom since that just looks broken. David Hollman (Talk) 15:29, 31 August 2010 (UTC)
I read the "navbox on every page" essay and I disagree with it. Putting "hundreds" of items in a navbox would be an example of Wikilaziness; instead of recommending to the reader the one or two links that most relevantly explain the subject matter, instead waste the reader's time with scores of items that have been free-asssociated with no obvious sequence or ranking by relevancy. An article is instantly de-orphaned if it has a link, either in-line with the text or else in a "see also". The essay admits that a "navbox" does the same function as a "see also" section, but without the benefit of an editor recommending items that are most particularly relevant to the matter at hand. Ultimately you'd just need one navbox saying "Other stuff" and put the whole of Wikipedia in it...after all, you might otherwise miss the connection between thermocouples and the Franco-Prussian War. (The advice to search for articles that "need" navboxes by an Easter-egg hunt using "random article" is precious...if you don't know what's relevant to an article, for goodness sake don't randomly put in a navbox!) --Wtshymanski (talk) 21:50, 31 August 2010 (UTC)
I'm sure most people would agree that these templates need to be well structured and not become random or poorly organized lists. However I don't have the impression that this particular navbox has these problems; although if you have any suggestions for its improvement I'm sure those would be welcome (Template talk:Thermoelectric effect - not the busiest talk page in Wikipedia). David Hollman (Talk) 20:36, 7 September 2010 (UTC)
Isn't that a little like asking for suggestions on improvements in the process for tanning baby skin for briefcases? Some things ought not to be improved. --Wtshymanski (talk) 20:47, 7 September 2010 (UTC)


My point was that unless there are specific issues with this particular navbox, I can't see any reason it should not be included on this page, particularly given that they are used throughout Wikipedia. While I appreciate your personal opinion that navboxes are not useful, I don't think that overrides the broad consensus which seems to be that they are. David Hollman (Talk) 21:11, 15 September 2010 (UTC)

It's been so long that I've forgotten what it looked like. Let's see, my specific issues and objections are:
  1. Object depicted isn't a thermocouple.
  2. Title of navbox is out of context until you read how a thermocouple works
  3. "Principles" section is redundant with principles explanation in the text.
  4. "Applications (general)" section isn't about applications, but randomly sticks in "Thermoelectric materials" and "thermoelectric cooling". And, it's not about thermocouples. Navboxes should be written by people who know the difference between "applications" and "materials".
  5. "Applications (Power generation)" just looks another of a bad and confusing set of headings - why are "applications" broken down this way? Aren't these more sensibly given in the article text?
  6. "Applications (Sensing)" again looks like a poorly-factored heading, and randomly lumps "thermocouple" and "thermopile" together.

Then there's the usual infobox nonsense letters at the bottom. "V D E" sounds like a German standards organization. It's big, it's internally confused, it's irrelevant, it's distracting, it's redundant...but it's a nice shade of blue. It's not an asset to the article. If there was such a thing as a good navbox, this wouldn't be it. "If a dozen Wikipedia editors do a foolish thing, it's still a foolish thing." I have removed similarly badly-constructed and ill-concieved navboxes elsewhere, with remarkably little comment. --Wtshymanski (talk) 21:52, 15 September 2010 (UTC)

It seems to me that this impression of usefulness of navboxes is highly subjective and only relies on the aspect that people like to create them. On Wikipedia people do all kinds of things to avoid writing a good article or creating good prose to explain subjects. Lists of facts, compilations of data, List articles, navboxes, etc. are a lot easier to create than writing something meaningful that others can understand and appreciate. Unfortunately navboxes usually don't explain much at all. I am not saying they aren't useful at all, but they should be extremely well designed in terms of link content and if possible they should fit into the See-Also sections or that general area, which is where WP puts that kind of functionality. The portal pages are for guided learning, not the articles. They should be reserved to subject matter content and have a link to their larger context in the See-Alse section. Kbrose (talk) 03:37, 16 September 2010 (UTC)
Examining the 'Benefits of navboxes' expose, it is pretty clear that the result of that study are bogus, statistically invalid, see my comments there. Kbrose (talk) 04:29, 16 September 2010 (UTC)
Hi, I made the navbox.
My original motivation was to make it clear what all the articles are related to the thermoelectric effect, because they're substantially overlapping, disorganized, and in some cases horribly inadequate. When the articles are all properly self-contained, organized, and interlinking, (someday haha), then the template will be become irrelevant except for the core articles on the thermoelectric effect. I've been gradually organizing and merging and deleting and interlinking and copy-and-pasting over the past couple years, but there's still a huge amount of work to do on this group of articles.
In this case (Thermocouple) we have a well-written and comprehensive article, so it's less important here. I'm not strongly opposed to deleting the template from this article. I am strongly opposed to deleting it in, say, thermoelectric effect (a core article relating to all the others), or thermopile and thermoelectric generator (which are crappy and not-self-contained), for example.
Ha ha, but I do know what the difference between applications and materials are. :-P If you look at the article thermoelectric materials, you will see that the topic is actually "materials for thermoelectric applications". Maybe I should rename it (again).
The point is that it's a list of articles in the heading of thermoelectric effect, and that someone interested in one may want to see all the other articles out there, since the text of the articles is still inadequate in many cases. The categories are less important. They could obviously be improved. "Applications (Sensing)" is especially bad, I agree with that. --Steve (talk) 07:27, 16 September 2010 (UTC)

(edit conflcit)

Wtshymanski, thank you for your constructive comments. I will add a note to the navbox talk page pointed here so perhaps they can be addressed.
Kbrose, I think you make some very good points, particularly the subjective impression created by navboxes (or anything else on WP for that matter). Obviously there may be many audiences for any given article, and it is probably impossible to please them all equally. Perhaps the jury is still out on the "best" way to organize information ("see also", project pages, navboxes, categories... etc.) but I think its positive for people to experiment, try things out, see what works, until a consensus is formed. I would think that the optimal way to organize things will vary among topic areas and this may have to be found by trial and error / iteration. David Hollman (Talk) 07:29, 16 September 2010 (UTC)
Have a look at Wikipedia:Disinfoboxes, too. --Wtshymanski (talk) 19:01, 16 September 2010 (UTC)

Some references?[edit]

This page seems to be very lacking in references, which is a shame as there is a lot of real-world information on it. Maybe the original contributors might wish to share their sources? (talk) 23:46, 27 October 2010 (UTC)

I agree. For example, user just corrected the maximum temperature for a Type J thermocouple from 700 C to 750 C. If there had been a reference to it is likely that the original error would not have occurred.

Here is a list of the Omega thermocouple reference tables.

Adding these as references and double-checking the Wikipedia page against them might be helpful. I am on a hot project right now, but if nobody else does it I will try to add the references and double check the figures n a week or two. = Thermocouple Type B (degrees C) = Thermocouple Type B (degrees F) = Thermocouple Type C (degrees C) = Thermocouple Type C (degrees F) = Thermocouple Type E (degrees C) = Thermocouple Type E (degrees F) = Thermocouple Type J (degrees C) = Thermocouple Type J (degrees F) = Thermocouple Type K (degrees C) = Thermocouple Type K (degrees F) = Thermocouple Type N (degrees C) = Thermocouple Type N (degrees F) = Thermocouple Type R (degrees C) = Thermocouple Type R (degrees F) = Thermocouple Type S (degrees C) = Thermocouple Type S (degrees F) = Thermocouple Type T (degrees C) = Thermocouple Type T (degrees F)

Guy Macon 14:46, 29 October 2010 (UTC)

What about the thermopower page?[edit]

When I hear the word thermocouple, I think about the device that is used to control temperature also Thermopower, where could a link to this page be put? — Preceding unsigned comment added by Scikris (talkcontribs) 00:23, 1 February 2012 (UTC)


Why the names or Types of thermocouples are random (K,E,S,B..), not serial(A,B,C,D..)? Is there any reason? Chinu giet08 (talk) 15:10, 10 March 2012 (UTC)

I don't know the history, but I think they were serial, and are listed now by their popularity (or other parameters, like alloying metal) rather than alpha order. Materialscientist (talk) 05:48, 11 March 2012 (UTC)

Insulation types[edit]

Note that copying tables like this [2] is not a copyright violation (such data are not copyrightable). I don't know whether this table fits in the article though. Cheers. Materialscientist (talk) 23:08, 5 December 2012 (UTC)

Are you sure? The page where it was copied from certainly says "© 2011 - 2012 Pelican Wire Company, Inc. All rights reserved." I would be surprised if someone spent a lot of time gathering all that information, and just because they published it in tabular form, there was no copyright protection for their company. Such information certainly needs wikifying though: what is the point of that column headed 'PART #' here? I'm sure there's something in WP:MoS about presenting info in ALL CAPS too. (Copied here from my talk page so that other editors here may comment too) --Nigelj (talk) 23:19, 5 December 2012 (UTC)

note on lead image[edit]


It's worth noting that the lead image at the present is a bit misleading, as the thermocouple is not being used at all to measure room temperature in that case. The reason I say that is that the multimeter is measuring basically zero volts out of the thermocouple, but it is performing cold junction compensation (using a second internal thermometer, based on thermistor or something like that). Thus the thermocouple has absolutely nothing to do with the temperature being displayed on the multimeter: I could short the inputs together using a simple copper wire and see the same reading.

It would be nice to have an image showing a multimeter measuring the temperature of something else which has a different temperature. --Nanite (talk) 22:21, 10 December 2013 (UTC)

The thermocouple is being used to measure room temperature. Assuming that the room temperature is indeed 19° Celsius, the type K thermocouple in use will provide an output of 0.758 mV of e.m.f. The junctions between the thermocouple wires/connector and the multimeter terminals will each provide an e.m.f. though as we do not know what the metallic composition of the terminals is, we cannot speculate as to the magnitude of these e.m.f.s. The cold junction compensation is designed to calibrate out these later two e.m.f.s leaving the meter to indicate the temperature represented by the e.m.f. of the thermocouple itself, in this case 19° Celsius. (talk) 14:59, 14 March 2014 (UTC)


Type-K Polynomial Coefficients 0–500 °C, 0.05 °C accuracy; for Tref = 0 °C[1]
n a_n
0 0 °C
1 25.08355 °C/mV
2 7.860106×10−2 °C/mV2
3 −2.503131×10−1 °C/mV3
4 8.315270×10−2 °C/mV4
5 −1.228034×10−2 °C/mV5
6 9.804036×10−4 °C/mV6
7 −4.413030×10−5 °C/mV7
8 1.057734×10−6 °C/mV8
9 −1.052755×10−8 °C/mV9

I removed the following table since it takes much space and adds very little to the article, especially since it only describes type K. And if we would have this kind of information for all thermocouples, the article would be full of wikitables. Anonimski (talk) 19:50, 4 January 2014 (UTC)


Thermoelectric voltage temperature difference[edit]

Example: I have a thermocouple with the hot junction at the temperature of 575 °C and cold junction at the temperature 550 °C. Let's say I measured the thermoelectric voltage U=0.1 mV. Now, I will take the same thermocouple with the hot junction on the temperature 50 °C and the cold junction on the temperature of 25 °C. The temperature difference in both cases is 25 °C. Will I measure the same voltage U=0.1 mV or not??? Is the thermoelectric voltage only a function of the temperature difference or because of the non-linearity of Seebeck coefficient I will get some other U?? Thanks. Tomáš. — Preceding unsigned comment added by (talk) 12:11, 25 September 2014 (UTC)