3mm TC vs 5mm TC temperature readings? - Page 2

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
Pressino
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#11: Post by Pressino »

Capuchin Monk wrote:Before I added a fan powered exhaust / chaff collector, my drum roaster was operating at very low velocity of vent air. At that time, I was getting 1st crack right around 360 dF every time. Now that I roast with more vent air flow, 1st crack is around 380 dF consistently. My guess on this is that the air circulation within the roasting chamber affects the temperature probe's sensitivity. :?:
Clearly that is true, which was the point of my assumption that the two probes were in exactly the same spot inside the roaster. The OP didn't say anything about changing the air flow in his roast chamber, so it's hard to attribute the wide difference (360F versus 390F) to merely a slower response time of the first probe. The difference in response time shouldn't be much more than a second or two, and certainly not minutes.

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hankua
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#12: Post by hankua »

The other aspect of the discussion is the "quality" of the thermocouples. Mill City uses affordable replacement thermocouples and I have bought them in the past, along with ordering inexpensive versions from China less than $5 each.

If one has rigged up a Phidget, you've noticed there's two solid wires; which are soldered at the end to form a junction; the part that starts the temperature measuring process. The junction is stuffed into a tube sheath, which can be of different diameters and thickness. There are a lot of variables with the thermocouples themselves apart from the roaster and the heat transfer from the faceplate.

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