Duplex K-type thermocouple for coffee roast control & monitoring

My Fracino Roastilino has two metal tubes into the roasting jug so I can insert the probe from the PID temperature controller plus a probe for the Amprobe logger to track and log the roast with the free-for-all Artisan software.

Of course one wants both probes to agree on the temperature even though they are inserted in two different spots. I found a way for them to agree by insering one a little more than the other, but sometimes one or the other probe would move a little and there would be a discrepancy of up to 10ºC.

Now, the people at TC Direct made me a duplex thermocouple in a single probe so both are feeling the temperature in the same spot.

I have tested the setup and around 20ºC they disagree about 2-3ºC but as the temperature rises they agree more and they are practically identical above 200ºC which is just fine. I can tweak the offset of one probe in the PID settings a little but that's not necessary.

Here is a short series of pictures documenting the modification:

Fresh from the unboxing

2x2 wires from the one probe
The probe with 2 TC's inside

Everyone wondering what color is + or - on this type probe, check their mug!

Connecting the wires to the plug for Amprobe

Previous setup with to probes

New situation: one dual probe

Connection points on the PID inside the roaster
Probe: green and white wires in the center

Testing: works! 


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