Thermocouple (type K)

[Noxx]

Hello guys,
For my electric kiln, I plan to build a thermocouple to monitor temperature.
I will build a sensor of type K (Nickel and Chromium wires) You can monitor temperature up to +1300C.
I also already have my Multimeter.

My question is, where can I get nickel and chromium wires ? I looked on ebay and I only found alloys, not the pure stuff.

Thanks guys.

 

[jimdoc]

Noxx,
I think it is called chromel try a search for that.
Also check Omega's website to see what you are
looking for omega.com and then see if you can
find it on Ebay.
Jim

 

[goldsilverpro]

Type K is chromel/alumel. While going to college, I worked for Honeywell and made custom thermocouples. Wish I had all the Pt/PtRh scrap they generated.

 

[Noxx]

You're right.
It's Chromel/Alumel.

I can't find Chromel neither Alumel on ebay...
Only crap going up to 200°C :?

I will look around the internet... I hope I'll find a cheap source !

 

[goldsilverpro]

Why not just buy an insulated thermocouple. Can't cost that much. You may have trouble getting a good junction if you try to make your own. They are usually butt welded.

 

[Noxx]

I found some not so expensive on omega.ca
What type should I get ? Do I need it to be insulated ?
Thanks

 

[goldsilverpro]

Here's a furnace type thermocouple with a pyrometer. The thermocouple in the photo is in the configuration you want. Ebay#160175175539 for $79.50. I believe it's only an indicating pyrometer. I don't think it's a controller. You might also be able to buy just a furnace thermocouple from a furnace company and use a relabeled millivolt meter instead of a pyrometer. You will also need some thermocouple lead wire, for best accuracy. The type K voltage is 41 microvolts per deg.C. Therefore, 100 deg.C would give 4.1 millivolts and 1200 deg.C would be 49.2 mV. A 100 mV meter would cover the whole temp spread.

If it is an electric furnace, I would suggest a controller. Otherwise, if you have to constantly adjust manually, there is a great possibility of overheating and a subsequent meltdown (not a pretty sight) of the lining and the elements, unless you keep a constant (and I'm not kidding) eye on the pyrometer.

 

[Noxx]

Thanks, I already saw this pyrometer. It's 100 buck shipping included so...
And I already have a precise Voltmeter.

But I found something interesting: 190171021082
The thermocouple of type K is included.

I think this would work. Now I have to understand how the controller works

Thanks

 

[goldsilverpro]

You're on your own with that thing. Seems too cheap to me. I don't know how it works either. Lots of connector screws?? I don't like the looks of the T/C.

I've owned several Cress furnaces. You might check out their site.

http://cressmfg.com/

 

[aflacglobal]

I have bought a couple of the cheap controllers off ebay, It's been awhile back. You will need the controller and a thermocouple which are included here >>> This is a cheap version of the real thing but should work for the application you need it for. You cannot run the full amps thru the controller or you will burn it up. Use a relay between the controller and the furnace.

Total cost $ 50 This will give you auto adjustment and you will not need to use a volt meter. I'd give $ 50 just to avoid the problems.

http://cgi.ebay.com/PID-TEMPERATURE-CONTROLLER-FURNACE-KILN-OVEN

 

[Noxx]

Thanks...
But I'm not really sure what relays are... Can I get them at an hardware store ?

 

[goldsilverpro]

It sure looks like that T/C threads into a wall, or something. It's like it was designed for a much cooler application than a 2000 deg F furnace. I would think it should be longer so you could measure the chamber temp.

Ralph, can you please shorten your link? Horiz scrolling is maddening.

 

[jimwig]

ebay ebay and if not there try ebay

this is gonna make you gulp or somthing - i am a dumpster diver and also visit all the recycling places and surplus scrap places.

found a roll of this red and white twisted pair wire. i suspected the best. i took it up to the man and he said $1.00 a pound and the hairs on the back of my hand fell singed to the floor as speedily got to my wallet.

must have been around 20 bucks.

took it to the ready reference department in my home/truck camper and sure nuff it was tyype K. not only type K but the kind that's covered with teflon. worth a bit more than the price i paid.

okay so i am holding onto this roll along with about a mmillion other items in my trouble making hhovel and --- and somebody stole it thinking it was copper insulated wire..... )(*^)(* and then i got mad #^%#$%^



well that is a true story and it makes me sick every time i recall it.

while i had it i gave away several feet every time a buddy even looked like he could use it.

this was all several years ago. that surplus place is a gold mine. or at least was.

so keep looking and the sky will open and rain thermocouple just be ready to lock it away.

 

[qst42know]

For your relay search Crydom relay on ebay. They are solid state no contacts to foul and no coil to fail. They will usually need a heat sink though. About ten bucks. They are quite reliable.

 

[skippy]

I've got a whole mess of fibreglass covered K thermocouple wire - more than I'll probably ever use
If anybody wants a length of it, I'll send some for the price of shipping.

 

[Wyndham]

The problem with the type K thermalcouple is that it become erratic at a bit over 2000F. If you are still looking for that though, look up pottery suply places a type K is cheap abot 20-30 $$$$. Type S is the Platium/rhodium big $$$$$ one that will be stable at least to 2500+F those are around $150.
check with http://www.bartinst.com/aboutus.html for controllersHope it helps Wyndham