how many thermocouples?

[boerwarrior]

Re: how many thermocouples?

KB

here is my digital thermometer.

I am currently using it to monitor my (daily) small curing fires to ensure I don't get too much heat too soon.

I stuck the end of the thermocouple near the fire I could get a nice high temperature reading!

It has a differential temperature capability (T1-T2) so I was wondering if I could somehow use that to ensure that I don't get thermal expansion (cracking) problems....

Sorry, "you can take the man out of the engineer but you can't take the ..." or something like that!

Neil

[kbartman]

Re: how many thermocouples?

KB

here is my digital thermometer.

I am currently using it to monitor my (daily) small curing fires to ensure I don't get too much heat too soon.

It has a differential temperature capability (T1-T2) so I was wondering if I could somehow use that to ensure that I don't get thermal expansion (cracking) problems....

Neil

Neil,
That is a neat inexpensive set you have there, $40 bucks you can't beat that. Where did you get?

It looks to me that the meter has three selection options. T1 or T2 and differential read out T1-T2. I'm sure you could better monitor a thermal temperature difference with the meter, and also calculated a differential expansion of some sort. The calculation is above my expertise but maybe along your line of work. I’m sure we can figure out something. Having some experience with temperature instrumentation and it uses, but far from being an expert. I’ll take a WAG. I would think that placement of T1 and T2 would be the first challenge. Where is the most likely place the greatest temperature difference would be found and would create thermal stresses during curing? I would think the top dead center of the dome would be the higher of the two. Where to place the second I’m not sure.

I’m thinking as stated by others that insulation would have the greatest overall benefit to keep these thermal stresses in check. The more I think about how to monitor these temperature differences is making my head spin. I’ll throw in the old BS excuse I have be known to use, and that works pretty well at work. As in most endeavors cost is an issue. “The cost to benefit ratio” a excuse that keeps me as busy as I want to be. They trusted I know what I’m talking about when I don’t have a clue. I hope they never call me out on it.

[kbartman]

Re: how many thermocouples?

Ok, here is some very brief research on the associated cost and my 2 cents.

Here you go KB,

I have 6 thermocouples

Two in the floor one at 3/4 inch from the surface and one 4 inch from the surface.
Two in the walls mid way up the wall 3/4 inch from the surface,one left one right.
One in the wall midway up 4 inches from the surface.
One in the wall midway up between the oven and the insulation 7.5 inches from the surface.

Well KBartman, I may actually put 1 or 2 in. Also how do you guys fit them so they're replaceable? Thermowells aren't very cheap or is there some sort if DIY thermowell or sleeve that's made out of copper pipe or something, what's the best thermowell to use?

Faith, you have some very nice highly accurate equipment but a bit above my price range. My goal is to impress my guests and get a fairly accurate temperature read out; at the same time have some techy fun along the way. I agree with the placement of your thermocouples and may throw in a few more for sh@ts and grins. Portability is not a concern of mine, I'm thinking of a permanent display. Not sure where to locate it, I don?t want to take away from the ambiance of the ancient oven.

I have to make a poke at davids on this.

It is rather incongruous to use electronic devices on an ancient oven. I find my stopwatch, observation????

I?m sure you meant to say sand hour glass instead of a stopwatch??lol???That being said I?ll find a inconspicuous convenient location to mount my techy toys.

To make a long story short I?ll get to the point. I think RichC copper pipe is a good idea. I think a roll of 3\8 tubing will do fine in creating an inexpensive thermo well and facilitate easy replacement.

I found an inexpensive 1\16 din single loop controller for $67 it will make a perfect readout display and provide for more techy future toys. And it also can double as a temperature control on initial curing. Not my idea though, I read it somewhere here in the forum. Throw in a cheap $15 selector switch and some cheap homemade thermocouples I?ll have all the other tech geek?s envois. All done under a $100.

Warning my estimates tent to have cost over runs. Consider my bathroom remodel a few years back at $3500 ended up being $12,000. Also my WFO estimate I told the better half is well past the $1500 ok to start project agreement. She?s always a good sport though. She'll always end up with a better project then first conceived.

[david s]

Re: how many thermocouples?

To make a long story short I?ll get to the point. I think RichC copper pipe is a good idea. I think a roll of 3\8 tubing will do fine in creating an inexpensive thermo well and facilitate easy replacement.

I used a copper pipe for the sleeve for my thermometer probe on my mobile oven and wish I hadn't. The thermal conductivity of copper is k value 400 W/mk That of stainless steel 16. A metal tube connecting the inside of the oven to the outside will conduct a fair amount of heat away from the chamber.I now always use stainless if fitting one on an oven. Another little problem I had was that the pipe fitted too tightly in the wall of the dome so every time the oven heated up it would push the pipe out of the outer shell a few millimeters each time. I had to fix it by making the hole in the inner wall slightly oversized so it would not grip the tube. That was about 4 years ago and it is still functioning well.

[kbartman]

Re: how many thermocouples?

I used a copper pipe for the sleeve for my thermometer probe on my mobile oven and wish I hadn't. The thermal conductivity of copper is k value 400 W/mk That of stainless steel 16. A metal tube connecting the inside of the oven to the outside will conduct a fair amount of heat away from the chamber.I now always use stainless if fitting one on an oven. Another little problem I had was that the pipe fitted too tightly in the wall of the dome so every time the oven heated up it would push the pipe out of the outer shell a few millimeters each time. I had to fix it by making the hole in the inner wall slightly oversized so it would not grip the tube. That was about 4 years ago and it is still functioning well.

All good info Dave. A little above my pay grade. I only install, repair, troubleshoot, operate and maintain the equipment. I try to leave the design and calculations up to the experts and learn from there mistakes. Usually the design team is long gone and we experiment to come up with solutions’ like your.

Ouch stainless tubing, you can now see the why my projects are plague with cost over runs.

Hope you didn’t mind the poke and hope you will be getting the hour glass out to impress the guest.

[mrchipster]

Re: how many thermocouples?

Ouch stainless tubing, you can now see the why my projects are plague with cost over runs.

Automotive brake line is stainless, hit the car junk yard and see what you can find.

Chip

[kbartman]

Re: how many thermocouples?

Automotive brake line is stainless, hit the car junk yard and see what you can find.

Chip

Cool, good idea

[david s]

Re: how many thermocouples?

[QUOTE=
Hope you didn’t mind the poke and hope you will be getting the hour glass out to impress the guest.[/QUOTE]

no worries. Actually, if I had an hourglass it would look really good perched on top of the oven. Thanks for the idea. I might look for one. I've been through all the temp measuring devices. I have a thermometer in the side of my oven another hole on the other side to take a kiln probe that has a porcelain sheath which is connected to an anologue (unpowered) read out gauge, an infrared gun and an internal air temp thermometer as well as a thermometer you stab into a joint of meat or loaf of bread. Increasingly use all of them less the more I cook. There is another trick apart from the semolina on the floor that the Italians used to use and that is to hold your fist in the centre of the oven until you have to take it out. 0 secs= pizza 1 sec= v hot ( roast Vegas, calzones 2-3 secs = foccacias, roast meats 4 secs = bread,puff pastry, general baking 6-7 scones, desserts etc. many = slow rost meats,drying etc.

[Faith In Virginia]

Re: how many thermocouples?

That is some great info about the tubing. I need to replace a thermocouple and while I was there I figured I would add a well. Mine are just inserted in the mortar joint, so good to know about the SS. Thanks

[kbartman]

Re: how many thermocouples?

Well KBartman, I may actually put 1 or 2 in. The one my refractory sells is this Digital Thermometer . I might just buy a few probes and install them as it should be very cheap. And then buy 1 digital readout like this, or even use my multimeter. Can anyone tell me, is it aKtype probe or what?

Richc,
Sorry I miss this question. Yes that meter does take a type K probe.

[UtahBeehiver]

Re: how many thermocouples?

KB,

I did use 3/8" 316 SS tubing I picked up as scrap. I place on probe at 1/2" from the inside of the brick and the other abt 1/2" from the outside of the brick. My plan for the TCs were to monitor brick heat saturation for future baking. Since I have barely finished the final coating of the oven I have not measured temperatures other than confirm the TCs work. I did not think it was worth while to monitor until all the insulation was on. I just use a laser gun for my pizza but starting to get a feel on how hot the floor is without the gun.

[Faith In Virginia]

Re: how many thermocouples?

Great placement Russell, With those two numbers alone you can tell where to stop your firing to hit your desired oven temp after the resting period. Just average the two numbers and that should be your total saturation temperature.

[UtahBeehiver]

Re: how many thermocouples?

Faith,
Thx but karangi dude advise me on tc placement if i were only putting in two.

[kbartman]

Re: how many thermocouples?

I'm thinking of buying this IR thermometer??..I need everyone?s opinion. Do you like it? Is the range high enough? If you know of a better one or better deal post the address, thanks all.

THERMO TECH Non-Contact Infrared Digital Thermometer w/ FREE Holster (-58? To +1022? F)

[david s]

Re: how many thermocouples?

I've got one almost exactly the same, but it's called ThermoWorks, but has the same range.It very easily "tops out". Don't forget that an IR only reads the surface temp so will record a higher temp than the oven really is at. The laser pointer on mine has died by the way, but it is independent of the temp measuring sensor so it still works.