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TC4 temperatures in Artisan artificially high with back to back roasts
Graeme Lindsay
Hi everyone,

This a a recent problem as I didn’t used to get this problem.

I’m using an air roaster, the TC4 and Artisan on a Mac.

With the first roast of the day, the bean thermocouple readings are what I expect with regards to Dry, First crack temperature and drop temperatures.

However, further back to back roasts result in the first crack temperature and drop temperature becoming progressively higher.

After 3-4 roasts the first crack temperature has risen by 8-9 degrees Celsius and a similar rise in drop temperature.

I have now placed an identical thermocouple next to the thermocouple that is wired up to the TC4. The extra thermocouple has been connected to a standalone Hylec thermometer and gives the expected dry, normal FC and drop temperatures.

So, it appears that with repeated roasts, the thermocouple connected via the TC4 to Artisan is progressively showing higher and higher temperatures.

Thoughts on what might be going on?

Many thanks.

Any chance to have increasing air temperature in the electronics box ? This would move the cold junction reference further and further...

Also, did you tried to cycle power between roasts ?
DIY: TO based IR 750g
Moded commercial: Dieckmann RoestMeister, Nesco, popper(s).
TC4ESP, MS6514, USB/Artisan/Apps, PID controllers
Grinder: MBK Feldgrind, mod'ed Porlex to 47 conical burrs, vintage PeDe Dienes, Kinu M38
Gaggia Mini, Aeropress, drip
Graeme Lindsay
Thanks Renatoa,

No I don't think it is a problem with the electronics box overheating.

Not quite sure what you mean by cycle, but it's an air roaster and the temperature drops very rapidly once the roast finishes. Also, I'm trying unplugging the USB from the computer to turn the TC4 after each roast but that doesn't seem to make a difference so far.

I have seen somewhere about how to setup Artisan to show the TC4 internal temperature. I'll try to do this to see if it is actually the onboard internal TC4 temperature that is actually rising and affecting the cold junction temp.
Yep, the unplug USB part is what I meant, to reset TC4.
This would be a photo of a tc4 placement on the device and a photo of a thermocouple connection.
In 99% of cases is the reason that why Renatoa writes.
There is little likelihood of error in a thermocouple or TC4.
You could also try adding a short jumper wire across any unused thermocouple inputs. I think I had issues once with charge building up over time on open connections? I think it was Jim who suggested I jumper the unused connections.
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