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I have just had a morning of heat treating some NitroV blades. Had two in the forge at a time to better control to plate quench with three plates. Put one on the base plate and a plate over it then another blade and the last plate. Put the SS wraped blades in at 1500F and ramped up to 1950-55 for 15 min using the gameco pyrometer and pressure guage to controll the temp as I normally do. First pair went well as did the second pair but the last lot did not as almost as soon as heat ramped up it started to fall back again (I thought it was freezing) so played with pressure to keep it right but where I usually only run in the 2 -5lb pressure range once the desired temp is reached this was needing 15lb to keep it there so after 4 or 5 minutes I switched it over to centigrade and found it was at 1170C or 2140F so quickly bought it back down and it stayed consistent at the 1066C for the remainder of the 15minutes ---so the question is --does these guages fail with long heat times and is there a better unit if they do?

Worst part was that I burnt the corner off my beard chercking things.

It is a 1300C/2372F guage

https://www.artisansupplies.com.au/product/digital-thermometer/

Edited by Garry Keown
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Usually the electronics are pretty robust.  What fails often are the probes.  It's hard to explain why you would get a bad reading in F but a good reading in C as all that happens is a change in the math being done by the processor inside.  The electronics won't ever fail in that way.  It would read incorrect in either scale.

 

The only thing that I can think of is that your thermocouple is going bad, and you jostled the wires just enough when you switch modes to get it working again.  I do see this when I have a probe going bad.  I'll get an off reading, and wiggle the wires.  Sometimes it starts working again, and will stay "Normal" for a while.

 

 

Edited by Brian Dougherty
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Thanks Brian. I do have a spare thermocouple so will change them out and it should be good to go again.

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Brian beat me to the response.  Pretty much exactly what I was going to say (but worded much better, I'm sure).  

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