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asudavew 11-29-2007 03:50 PM

thermocouples... same o same o
 
I'm sure this has been covered..
But...

What temperature do thermocouples need to be rated to?

If they are embedded in the floor bricks .. say 1/2" from the oven floor, how hot will they get?
And if they are embedded in the dome bricks.. say 1/2" from the inside surface of the upper dome... how hot will they get?

Will a 900f probe work, or do I need ones rated to 1200f or more.



I need your help here Jim! .. Time to earn that new title! ;)

Actually, I would appreciate any help. :D

Thanks everyone!

Dave

Versachi 11-29-2007 05:29 PM

Re: thermocouples... same o same o
 
Hey Dave, I have two thermos in the floor and one is about a half inch below the surface. My thermos are rated for 1000F and I have had it read over a 1000 a few times and once 1035F. It is amazing the difference in temp between one near the surface and one just a couple of inches below. Of course I didn't figure that out. It was from that guy that just past 1000 posts....what's his name again? I am starting to think that his name is "thanks again Jim":D

Cheers, John

ricocamus 11-30-2007 05:45 AM

Re: thermocouples... same o same o
 
Since you bring up the idea of thermocouples, I'd like to ask what the general experience is between theromocouples and the infrared thermometers. Are they interchangeable? Which is better

asudavew 11-30-2007 06:14 AM

Re: thermocouples... same o same o
 
Quote:

Originally Posted by ricocamus (Post 20286)
Since you bring up the idea of thermocouples, I'd like to ask what the general experience is between theromocouples and the infrared thermometers. Are they interchangeable? Which is better

I think the main difference is thermocouples will give depth readings and the infrared themos will give you surface temps.

asudavew 11-30-2007 06:15 AM

Re: thermocouples... same o same o
 
Quote:

Originally Posted by Versachi (Post 20263)
Hey Dave, I have two thermos in the floor and one is about a half inch below the surface. My thermos are rated for 1000F and I have had it read over a 1000 a few times and once 1035F. It is amazing the difference in temp between one near the surface and one just a couple of inches below. Of course I didn't figure that out. It was from that guy that just past 1000 posts....what's his name again? I am starting to think that his name is "thanks again Jim":D

Cheers, John


Thanks John. So do you think I would be fine with thermos rated to 1000f?

CanuckJim 11-30-2007 06:28 AM

Re: thermocouples... same o same o
 
Yeah, who is that guy? Masked man, likely. Anyhow, my thermos are rated at 1000 F, but I've had them reading as high as 1050 with no ill effects. Usually, the floor reading is in the 900 range before I let the oven moderate. As I see it, the real difference is that thermocouples will give you reliable temps at various spots in the brick and any additional mass. The guns will supply surface temps, but they won't say if the brick and mass have been saturated.

Jim

asudavew 11-30-2007 07:33 AM

Re: thermocouples... same o same o
 
Quote:

Originally Posted by CanuckJim (Post 20291)
Yeah, who is that guy? Masked man, likely. Anyhow, my thermos are rated at 1000 F, but I've had them reading as high as 1050 with no ill effects. Usually, the floor reading is in the 900 range before I let the oven moderate. As I see it, the real difference is that thermocouples will give you reliable temps at various spots in the brick and any additional mass. The guns will supply surface temps, but they won't say if the brick and mass have been saturated.

Jim

Good enough.

Thanks Jim. I didn't want to order the wrong ones.
Now.. I just need a source for J types.....
:confused:

Versachi 11-30-2007 07:07 PM

Re: thermocouples... same o same o
 
Can you get high temperature J thermocouples? I thought that K's are for high temps. I could be wrong and I am not an expert by any means. Take a look on ebay for some thermocouples. I bought mine there and they were 10 or so bucks a piece.

Cheers, John

wlively 11-30-2007 07:34 PM

Re: thermocouples... same o same o
 
J-type temp range is 32 <-> 1380 deg F 0 <-> 750 deg C.

K-type temp range is -300 <-> 2280 deg F -200 <-> 1250 deg C.

The temp error is the same for both (2.2 deg C or 0.75% whichever is greater), so the K-type is much more widely used and easier to find.

Problems with J type is iron is one of the metals so is prone to corrrosion in wet environments. Is less widely used and on the way out, as it were. Also, if embedded inside the brick it is not a concern with our use, but if you choose to leave the tip exposed passed the brick exceeding 1390 deg will induce permanent errors in the output. IE; no longer accurate.

For those who want more education, this is a good link.
Thermocouple application note from Pico Technology

ricocamus 11-30-2007 09:43 PM

Re: thermocouples... same o same o
 
Quote:

Originally Posted by CanuckJim (Post 20291)
Yeah, who is that guy? Masked man, likely. Anyhow, my thermos are rated at 1000 F, but I've had them reading as high as 1050 with no ill effects. Usually, the floor reading is in the 900 range before I let the oven moderate. As I see it, the real difference is that thermocouples will give you reliable temps at various spots in the brick and any additional mass. The guns will supply surface temps, but they won't say if the brick and mass have been saturated.

Jim

Thanks for the enlightenment on what the thermometers will do.

Now, for another 'serf' question - why do we need to know if the brick has been saturated? Isn't the surface temperature what counts for cooking?


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