Verification Thermocouple?

[DanF]

With the somewhat recent threads on possible inaccurate temps in heat treating kilns, I am considering installing a second, separate TC to verify my actual temp is within a reasonable variation of the set temp. I have everything needed (type K TC and an inkbird pid that will only be used to read the temp).
Before I go drilling a hole in my kiln I just wanted to check with the more experienced here to determine if this is necessary (or a better practice), and, would it be better to drill down from the top (possibly weakening the kiln ceiling?), or, drill in through the door?
Thanks,

 

[DAMNENG]

If you don't want a permanent installation, Run the check TC through the door and place it along side the internal Tc. Then check at sever different temperature points. For heat treating, repeatability is more important than accuracy on the TCs.

If you are going for permanent and expect them to read the same or similar temperatures you need to place them as close to each other as possible. First I would run the check listed above for temperary then install them permanently after confirmation they read satisfactorily.

My controller TC is in the center of the back of the kiln. My check TC is in the middle of the top of the kiln. They vary by about 45°f at start up and settle down to about 8°f difference when the temperature stabilizes at 1975°f.

I'm sure someone else will dissagree with this, but this is what I have set up.
Hope this helps you.
Jim A.

 

[DanF]

Thanks Jim, I'll go through the door. I'm not expecting the TC's to match, just trying to be assured (or as assured as I can reasonably be), that my ht protocol is what I expect it to be.

 

[John mc c]

I would also check the temp difference between the ovens TC and the temp at the back of the oven Dan

 

[scott kozub]

I tried the salt melting idea to check my homebuilt heat treat oven with minimal success. Then I took a simple steel and heat treated 6 coupons at varying temperatures around the ideal temp and checked hardness and grain size. This was much better.

 

[DanF]

For better or worse it's in there.
I tapped a couple screws in because the tc wanted to cant downward when it was free floating. Will mount the pid as soon as the wire gets here.