Pyrometer

Try EBay Bubba to buy one. I have one that I use plus I have a digital controller for my forges.
 
Pyrometers work by connecting output light to temperature -- through very well-known and well-understood physical properties.

So long as the calibration holds and the instrument's dynamic range is appropriate, it will work. The number it gives you is not perfect, however -- it will be correct within a certain range (error bars) that should have been specified by the pyrometer's maker.
 
Oldphysics, I thought a thermocouple pyrometer measured the difference in electrical current passing through the heated part (variable), as well as the non-heated part (control), and came up with a reading based on those measurements.

Is there such thing as a light based pyrometer too? Hey, anyone ever use a laser thermometer to measure blade heat? I wonder if it's accurate.
 
Mike Arsenault said:
Oldphysics, I thought a thermocouple pyrometer measured the difference in electrical current passing through the heated part (variable), as well as the non-heated part (control), and came up with a reading based on those measurements.

Is there such thing as a light based pyrometer too? Hey, anyone ever use a laser thermometer to measure blade heat? I wonder if it's accurate.
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Darn. Apparently should have read the original post more closely. Didn't realize he was talking about the old thermocouple-based pyrometers -- they do indeed read differential currents.

I was referring to the optical pyrometer. Yep, they do make 'em and they are non-contact. Had my first one in my lab back in 1976 I think -- real happy to get it because it was so easy to use. Had to keep it calibrated, of course! And no good for pieces at low temperature -- not enough light output as grey-body temperature is just too low.

Should be able to use an optical pyrometer to measure blade heat...but not sure what a laser thermometer would be!:) As I recall, the optical pyrometer was (and probably is) fairly expensive.

Here's a link to some basic info on the optical pyrometer: http://www.temperatures.com/opyro.html

By re-reading it I learned that they are being replaced by 'radiation pyrometers': http://www.omega.com/literature/transactions/volume1/thermometers1.html

From their description, radiation pyrometers or thermometers should be more accurate and precise than optical pyrometers -- didn't come across any definitive numbers in the little time I had to research the question.
 
still havent answered my question much. im looking at one on ebay that uses a ceramic covered thermacouple but it has a couple of chips of the ceramic missing. im wanting to know if i can use this in my gas forge.
 
Well, I'm glad I asked!

The only reason I did is 'cause I only knew about the one type of pyrometer we looked at in college, the thermocouple type. I didn't even know what a pyrometer measured until about 2 months ago! ( Maybe it gives a reading on 8 year olds stealing matches...? :o :D ) I find that's the best way to learn quickly though, say something erronous around someone who actually knows...
 
Yeah, I'm not sure if it's actually called a laser thermometer, but I've used one before for checking heat in hard to reach bearings/gearboxes. It's a little gun with a laser in it, it gives a digital readout of the temperature of the object it's pointed at. I think the one we had was worth about 200 dollars.
 
Mike Arsenault said:
Yeah, I'm not sure if it's actually called a laser thermometer, but I've used one before for checking heat in hard to reach bearings/gearboxes. It's a little gun with a laser in it, it gives a digital readout of the temperature of the object it's pointed at. I think the one we had was worth about 200 dollars.
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Chances are the laser was just an alignment tool -- to make sure the optical pyrometer was taking readings precisely where you wanted it to. That was occasionally a problem in the old days. Glad to see prices have come down...if I recall right, the one I used cost us about $1900.00.

If the thermocouple-based pyrometer has chips in its ceramic coating, I would be nervous about using it in a gas-fired forge. The thermocouple itself might not survive direct exposure.

Do the chips go all the way through the ceramic, exposing the thermocouple?

Also, check to see the maximum temperature the pyrometer is rated to measure. Don't use it above that temperature.
 
i already checked the temp rating on it in the pic. it goes up to 2000. i figure that its well worth the $17 plus shipping if all i have to do is replace the thermocouple. and yes it goes all the way thru to the thermocouple. in the pic the person showed it next to their digital pyrometer that was on the kiln and they were reading the same.
 
17? I say go for it -- give it a try. With just a little luck, it will do the job for you.
 
Well, the K range is up to 2000F, but you will find the TC degrades pretty rapidly up there in the hostile forge environment. The ceramic is to shield it from this, of course, which will help. Some guys shield TCs in SS tube. Keep in mind TC probes are consumables. You may need to replace them fairly regularly at those temperatures.

In my opinion (FWIW), a TC in the forge (for general forging--even forge welding) just isn't necessary.

If you're using your forge for HT, then I suppose it could be useful.
I run digital controllers on all my salt pots and ovens, but these all deliver heated atmospheres uniform enough to make a reading of +/- 10 degrees relevant. Most multi-use forges are not all that uniform so you find yourself measuring with a micrometer and cutting with an axe, so to speak.

A lot of guys do it, but if I was on a tight budget, I wouldn't buy a pyrometer to stick in my forge.:)

Just a thought.
 
This analog thermocouple type pyrometer measures up to 2400 F> It works very well in a forge. You can put shunt on the meter and halve the reading and get up to 4800 F. ( I doubt the thermocuple would stand that but it does let you go on up to say 3000 F)

http://www.sundanceglass.com/pyrometer.htm
 
are there any out there that i can just hook up to a micrometer with the two leads? i can get a micrometer easily. im still on a very tight budget but i would like to get my forge to a proper temp instead of just guessing.
 
You can buy just the thermocouple from the same place listed above for 19 bucks. A digital voltmeter should read the voltage. Youd have to extrapolate it to temperature.
 
PimpinSquee said:
are there any out there that i can just hook up to a micrometer with the two leads? i can get a micrometer easily. im still on a very tight budget but i would like to get my forge to a proper temp instead of just guessing.
Click to expand...

I think you will find that judging the temperature of your workpiece (not to be confused with the temperature of the atmosphere where the TC is located) just isn't a matter of guess work.
 
tnmike said:
You can buy just the thermocouple from the same place listed above for 19 bucks. A digital voltmeter should read the voltage. Youd have to extrapolate it to temperature.
Click to expand...

how would i go about reading it to know what im reading? and be able to know what temp im at. also remember im using a gas forge.
 
Not a micrometer, Jacob... that measures thickness. Might want one of those, though.
You were asking about a multimeter or DMM, I'm sure. Some are capable of direct thermocouple input. fluke makes a converter to convert the thermocouple input to a voltage output for DMMs. about $99, though.
Why not get a PID controller? If you ever think you want to control the temperature of an oven or forge, it's the way to go.
Here's a fairly inexpensive one that would meet your needs...
add a heavy duty type K thermocouple, and you'd be good to go.

As far as the optical pyrometers, they are expensive, and the newer IR pyrometers made by Raytek and the like are pricey, and would be of limited use looking into a forge. It wouldn't see the workpiece temperature, but the flame temperature, which is much higher...
 
When I built my forge I got a thermo couple with the ceramic disk cover and a swinging needle type readout. I workd fine and has for a while now, The thermo couple is slowly disappering but, that is how it works. I don't need it much now because I have learned how my forge responds and can look inside and give you a good quess at the temp. I do not use it to heat treat. I did order the controller mentioned in this thread as I think it will be perfect for builting a electrical salt pot to harden with and it seams that is the best hardening method. I have a small toaster oven that I modified to uses as a tempering oven.
 
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