Furnace calibration

[Fox]

As I work more and more with the accuracy of my heat treatments, I am wondering how often I should check the calibration of my furnace. How do most of you do it? I was looking at the Fluke 50 series and wondering if that unit would do the trick? It is reasonably priced and I have a lot of faith in Fluke products having used them extensively in the past for other needs. Do you guys use a separate probe, or just hook to the thermocouple and adjust heat settings for the error factor? I am inclined to use the latter since it would be difficult to insert a separate probe into my Evenheat. Of course, this brings up another question: how often would you get the Fluke calibrated?

Never ends when you start down the scientific road, does it!

All input welcome and appreciated. Thanks in advance.

 

[fitzo]

I use a second probe/meter to provide an independent measurement. I drilled two holes in my Evenheat (one side, one thru door) the size of the probe and worried it through for a relatively snug fit and plug the unused hole with Kaowool. I tried to position the probe right where the blade would be. Thermocouples are typically +/- 3% so there can be substantial differences and they are still reading the "same" temp. I average the two readings and shoot for my temps to be low-midrange for a particular steel austenitization. Subsequent testing with a Rockwell tester insures I had adequate temps.

I use Omega but the Fluke stuff is just as good for our use, IMO.

Bear in mind that thermocouples degrade with time and don't necessarily outright fail. After a time they will give bad readings, and i found out the hard way. That is why I now use two separate measurements.

 

[Fox]

After I thought about it, I figured I would have to drill a couple of holes in the Evenheat. Did you use the K-type air probe?

 

[fitzo]

Yes, I have k-type Inconel clad 2500F thermocouples from Omega and use an Omega thermometer/multimeter.