Help installing thermocouples, datalogging drum roaster


New member
Nov 21, 2011
Albany/Lebanon, Oregon
I've decided to finally join the ranks of the dattalogers!

Looking for help upgrading my setup. I've been roasting with this setup, minus digital data-logging, for a few years now, with the help of Rain Frog's Roastmaster iPad app (highly recommend for starting out!)

I apologize in advance if I'm all over the place. I have lots of questions.

What I have:

- 1K drum roaster (see pics), motor geared to 60rpm
- Artisan roasting software: Haven't used it yet.
- Mastech 6415 (in the mail!) Dual-channel temp sensor, USB interface Meter.

What's the best way to get a good BT & ET read?

Should I upgrade the probes from the standard flimsy wire k-type (exposed?) sensors, to something sheathed?
- Is there a way to hack/rig the flimsy wire K sensor to a manual thermometer sheath?
- There are two manual thermometers installed (see pics), should I just use those slots?

Are ungrounded thermocouples better for roasting, vs. grounded or exposed-wire, and does diameter of probe matter much?

Also, on a slightly different topic:

Airflow/vent: Currently, when approaching 1C, I have to lift the doors on the sides of the machine to slow the roast down (pain in the A, but usually gets the job done). Any recommendations?

Can I just rig up a vent-tube to pull air through the bean-chute (subsequently doubling as a chaff collector)?

(Full circle)
If I can control air-flow through bean chute, would this give me better overall controll of roast, including more accurate BT reading?

Thanks for reading.

- - - - -
I call him Brave, the little Roaster.
Brave 1.JPGBrave 2.JPGBrave 3.JPGBrave 4.JPG
I didn't make him. Wish I had. I just added the motor. It came as a hand-crank, so I switched the shaft around and added the pulley. A guy on ebay, from Texas, who went by the name Lloyddster, built it. Not sure what happened to him. Seemed to have disappeared. If anyone knows how to contact him, let me know! I need to thank him and send him some beans.


New member
Nov 21, 2011
Albany/Lebanon, Oregon
It's been a while, and I've since built a chaff collector/air flow vent, and purchased new thermocouple probes (just arrived in the mail today! WAHOO!!)

Needing assistance installing the new probes in the most efficient place, and calibrating (is that the right term?) their readings to create a more accurate curve.

My K-type probes are...

5mm diameter
5cm long
6.7mm thread

5mm diameter
10cm long
13 mm thread

Not sure if it's gonna be a problem that one is grounded and the other isn't . (I understand that grounded reads more erratic, and ungrounded is more slow-and-steady.)

Since these probes were cheap, I was hoping to get a feel for the 2 different types, and play with interchanging them between BT and ET to see which gives better results.

Anyway, I'm looking for advice on where to place them, and which length/type (5cm grounded vs 10 cm ungrounded) is better suited for which reading (BT vs ET).

My machine:
1k capacity,
stainless solid steel drum with mesh back.
It's pretty much a thick, square metal box--like a heavy duty smoker)
(Pics/details about my machine are in my older post above.)

I mentioned to a roaster friend that my current ET thermometer is at the far top corner of my machine (see pics above) and they said it may not be reading a true Environment Temp. Any thoughts there? Should I be trying to get closer to the back of my drum where the heat enters?

Also, when I get a negative ("-") reading, does this mean I hooked the wires up backwards? ...I'm gonna go reverse them and see if this changes.


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