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12/05/2023 2:44 AM
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Curious profile
Hello dear home roasters, I wanted to show you a profile obtained with my 1.2 kg drum roaster.
I am randomly getting a disorienting temperature indication, where the exhaust temperature seems to be a mirror image of the bean temperature. Have you ever had anything like this?
Is it a consequence of something real inside the machine or is it a spurious?
This roasting was done at 70% capacity of the machine as I usually do, this is the second time I see something like this in my machine.
I measure temperature with thermocouples type K and through max6675 converters I send them to arduino and from there via modbus I communicate to Artisan.

Profile 021_23_07_23 With "Mirror" phenomenon.
Profile 020_23_07_23 Without phenomenon (similar conditions as 021_23_07_23)

My hypotheses are
1- Spurious measurement
2- Sudden change in ventilation
3- Some inherent coffee issue

I was present my machine in this post.
msantillan attached the following images:
021_23_07_23.png 020_23_07_23.png

Edited by msantillan on 07/25/2023 6:58 AM
Obvious question: how old are the thermocouples? Some of the bonded to the shroud have a very short life as well as the unbonded fast response bare ones.

In space, sometimes we replaced them after one thruster firing cycle
How could be related to aging the curios behavior of the opposite direction, but perfectly matched and mirrored spikes ?
Related to age both ET and BT have 25 roast cycles. ET is bare and BT with a 3 mm diameter metal cover.I don't think it is the cause.
I tried turning the air fan on and off in the middle of the process and there was no disturbance.
I observed a similar effect but the opposite when I took out the tryer. Since the suction in the drum is lowered (BT goes up) and the intake of fresh air to the exhaust increases (ET goes down).The tryer is located near the exhaust pipe.
I am attaching a profile of a previous roast, in which this phenomenon was not observed. The roast is with the same amount of beans.
This looks like an issue I had with my setup, phiget to the thermocouples.

If I remember Renatoa's comments were much the same.

My issue was poor connection to the phiget. I cleaned the stray fibers, I applied some heat shrink to keep it clean and I check the connection every so often and have not had this issue since.

Double check the thermocouples type K and through max6675 converters connection just to eliminate them.
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