Need to measure up to 1200 degrees F - help

[jgravatt]

Does anyone have any thoughts about how I could measure temperatures up to 1200 degrees F? I could buy a pyrometer or piece one together with a thermocouple and multimeter, but just wondering if there is an easier way to do it.

Thanks,
Jeremy

[Ivan Seeking]

At 1200F it is probably easiest to use a thermocouple. What is the application?

http://www.omega.com/toc_asp/subsectionSC.asp?subsection=A01&book=Temperature

[jgravatt]

I built a kiln to anneal glass, but I need an accurate way to measure temperature so I can set up a firing schedule. I suppose I could use a small 3 mil rod and if it slumps then the box is too hot, but that takes alot of trial and error.

Jeremy

[Ivan Seeking]

Originally posted by jgravatt
I built a kiln to anneal glass, but I need an accurate way to measure temperature so I can set up a firing schedule. I suppose I could use a small 3 mil rod and if it slumps then the box is too hot, but that takes alot of trial and error.

Jeremy

Usually, kiln applications do use thermocouples. The page linked shows some options in your temp range. Also, you can buy temperature control modules very cheaply now. They can read the thermocouple directly [no amplification] and they also provide discrete contact outputs for simple on/off control. They can also provide one or several temperature zones and ramp schedules [allowing for a controlled ramping up or down of the temperature as is also often required]. Omega [linked] or nearly any industrial electrical supply house sells these controllers. You should be able to purchase one for about $60 - $80.

[Ivan Seeking]

Two additional notes: If you buy a controller make sure that it is compatible with the thermocouple type selected [most likely type J, K, or E in your case]. Nearly any controller accepts types J and K, but any other selection could create a compatibility problem with some low cost controllers.

Next, you need to be careful about the contact rating for an inductive load like this. I assume that your heater draws about 15 amps at 110 or 220VAC. This could exceed the standard contact rating of 10-15 amps for purely RESISITIVE loads. You need to oversize your heater control contacts by at least 50 - 100%. You can also buy relays with magnets inserted that act to quench the back EMF discharge; thus protecting the contacts from damage. [Edit: strike that comment. True but not really applicable here]. The kiln may also have an intervening contactor that makes this a moot point.

[jgravatt]

Thanks for everything. I fould an old analog pyrometer with a type k thermocouple on an auction for $12. Hopefully it will work, anyway it will be worth the risk of $12. As for the controller, I won't get one until I build a larger kiln - probably within the year as my current kiln works fine. Thanks.

Jeremy