Having trouble understanding what the difference is between a BT, ETTA, and MET. Is it just based on where the TC is placed within the roaster?

Are thermocouples just wire like in appearance? What are the ends like? I have a Huky on the way and want to try to have a better idea how the thermocouples work before it arrives. I will be using the center 304 recommended by mr.li. Will it be easy to distinguish which end of the Tc goes in the roaster and which end into the center 304?

Thanks,
Blake

Phidgets will give you a great base to start from, in order to learn more about them.

http://www.phidgets.com/docs/Thermocouple_Primer

A BT probe sits buried in the bean mass as much as possible. I'm not sure in what context you've seen ETTA, because it's not a common parlance. But ET means environmental temp, and needs to measure the environment inside the drum, but away from the bean mass. MET is the highest environment temp the beans are exposed to. A more useful temp to measure is Exhaust Temp, the temp of the air as it exits the drum. Many roasters, especially small scale ones have wildly different temperatures depending on where they're placed. An Exhaust Air measurement can ameliorate that a bit. Case in point, on my Quest, I can get wildly different environmental temps just based on where it's located in proximity to the heating elements, even though they're outside the drum.


All three can be the same probe type, thickness, etc, just their placement is separate. But in the case of my system, I use a thinner probe for BT than the others.

The thermocouples are pre-installed by Kuanho. The thermocouple is a "K" type with a mini "SMP" style quick-disconnect end. I removed the qd ends because I direct wired the tc's into the Arduino/TC4 board that I'm using to interface with the Artisan app.

If you want to know a little bit more on thermocouples, Omega is a good place to start.

Thank you Etta was a typo. So the three metrics all just depend on where the probe is set? BT probe sits within the beans, would the be considered the very center of the drum? And the ET probe would also be in the drum but closer to the surface? And the MET would be outside the drum, in between the drum and the heat source? Is my understanding correct?

The BT is set at about the 7 o'clock position, the ET usually replaces the analog thermometer. The MET Kuanho mounts outside the drum in about the 2 o'clock position.

Here you can see where the three t/cs will be

MET is at the top right just next to the input/exhaust pipe.
ET is almost directly below it (where the analog thermometer was).
BT is behind the handle of the trier.

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