I just wanted to mention a small inaccuracy in the video regarding thermocouples. You said that the thermocouple (Type K) couldn't go any higher than 250 deg.C.
This is incorrect, all Type K thermocouples are accurate up to 1350 deg.C and down to -200 deg.C (per definition/standard they are all made from the same alloy), and all good thermocouple meters should also be accurate in that range.
Fluke think that you are very wrong indeed:
http://www.fluke.com/fluke/auen/accessories/temperature/80bk-a.htm?pid=55348
260C max
It's not often that one finds a subject related to electronics that
"Dave Jones himself" does not already know everything about already! (I mean it as a compliment)
Just to illustrate my point: I fetched one Fluke thermocouple of the same type you had in the video (Fluke printed on the black connector), and one thermocouple that is rated to +1350 deg.C from the manufacturer (Omega USA brand). See images below:
- Test in water to confirm their accuracy - Both showed similar reading of 20.1 - 20.2 deg.C
- Test with torch up to ca 1150 deg.C - Both showed similar reading of ca 1150 deg.C (depending on how well I managed to position the torch).
- Verification in the same water again to confirm that their accuracy had not been changed, they both showed the same temperature as they did initially.
Keep in mind that the type K alloy can not handle 1350 deg.C continuously for many hours/days depending on the atmosphere, since it might become oxidized or reduced. For continuous operation at these temperatures the two wires are often covered by a metal tube made out of Inconel or other type of superalloy (the Omega branded thermocouple in the images below is covered by such a tube, hence why you only see one rod and not two wires)
I still believe that Fluke:
- lists the measurable range based on the temperature rating of the insulation (so that it does not melt or crack)
- or purposely list a lower range than it can handle so that they can charge more money for other probes. (does not feel like something a serious manufacturer like Fluke would do)
There is one detail that is important to mention, there are also compensation and extension grade thermocouple wires. These consist of a different alloy with similar Seebeck coefficient close to ambient temperature, and have the purpose of being able to extend the length of the wires from a thermocouple.
They are however not intended for forming the tip/junction where the actual sensing takes place, but can in theory form a very crude thermocouple that would be somewhat accurate close to ambient temperature.
Source:
Have a master degree in metallurgy and a Ph.D. in materials science. I work at a company that, among other things, produce thermocouple cables/wires.