thermocouples... same o same o

[asudavew]

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.

Thanks everyone!

Dave

[Versachi]

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"

Cheers, John

[ricocamus]

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]

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

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

[asudavew]

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"

Cheers, John

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

[CanuckJim]

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]

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

Good enough.

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

[Versachi]

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]

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&#37; 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]

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

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?

[dmun]

Re: thermocouples... same o same o

A brick wall that's hot most of the way through will stay hot and radiate heat for a long time. One that's hot on the surface will cool down quickly.

[ricocamus]

Re: thermocouples... same o same o

A brick wall that's hot most of the way through will stay hot and radiate heat for a long time. One that's hot on the surface will cool down quickly.

OK, think I am beginning to understand.

The objective, then, is to get high temp (900) on the surface and in the brick. If you do that, then you can bake pizza all night long! Because the hot bricks will keep the surface temperatures hot.

[CanuckJim]

Re: thermocouples... same o same o

Rico,

Depends entirely on what type and how much cooking or baking your want to do. For a pizza bake of an hour or so, surface temps are all you need. If, however, you want multiple bakes, or you have added additional mass for heat retention over time, then deep brick or mass temps are very important. My oven is high mass, and I do multiple bread bakes over six to ten hours, so mass temps are just as important as surface temps. Next, when the mass has dropped to acceptable levels, I'll put in the roast or the chicken or the....

Jim

[ricocamus]

Re: thermocouples... same o same o

Rico,

Depends entirely on what type and how much cooking or baking your want to do. For a pizza bake of an hour or so, surface temps are all you need. If, however, you want multiple bakes, or you have added additional mass for heat retention over time, then deep brick or mass temps are very important. My oven is high mass, and I do multiple bread bakes over six to ten hours, so mass temps are just as important as surface temps. Next, when the mass has dropped to acceptable levels, I'll put in the roast or the chicken or the....

Jim

Hmmm, getting more complicated but more interesting as well. Now I think I have one more item to add to the buy list.

Is it just me or do these projects really have a way of growing on their own. Sort of like pizza dough in the rise stage . . .

[jcg31]

Re: thermocouples... one more time

Sorry to put you guys through this again, but I have flipped on the thermocouple issue and am now contemplating it once again. I have searched all the posts and get the fact that I should be looking at K type thermocouple, but I don't see much out there on a preferred display. I would be looking for a wall mount (that I would enclose using CJim's approach) with four inputs, data tracking would be cool so a port out would be great but not essential. Anyone have any preferences?

Also (great timing) my dome is up, so in placing a thermocouple in the floor am I better coming in through the soldier course and floor brick (and how far in do I need to come to be meaningful), or up through the concrete and vermicucrete?

Thanks for any help,

Jim