Bean surface temperature with infrared thermometer

[jacobk]

I am waiting on my new infrared thermometer and would like to use it for measuring the bean surface temperature when I roast in my Behmor.

Can anyone give me some advice on how to get the best readings?

Can you measure accurately though the glass door?

Thanks
Jacob

[Ben]

Hi Jacob. I've found an infrared thermometer does not work well for measuring roasting beans in a Behmor. Even with the door open, the mesh of the drum affects the reading. I didn't try through the door, but I'd imagine it's even worse--especially as the glass gets dirty during roasting.

The only way I've seen to effectively measure the bean temp in a Behmor is to mount a probe through the side wall and into the drum. John shows photos of it here:

chocolatealchemy.com/blog/2017/1/19/ask-the-alchemist-191

I thought he had a page showing how to do it, but I can't seem to find it. If you're interested, you can google around and find some posts on some coffee forums showing different ways of doing it.

[jacobk]

Thanks a lot Ben. I actually already installed a probe like that, but I am experiencing some oscillations in the first part of the roasting - So I thought it would be nice with a second probe to "validate the results. But it makes sense that the drum affects the reading.

[bmikiten]

Jacob -

I have a few Behmors and there are temperature variations depending which program you are using. The heating cycles aren't always consistent but fortunately, it doesn't really seem to be large enough to affect the final product. As Ben noted, iR thermometers aren't a great idea. In fact, if you take two or three of them, you'll find that they can often disagree especially if they are the low-cost types. In-bean solves most of these issues as long as your probe is correctly connected and located.

Brian

[Sebastian]

Since 100% of the nib is below the surface, why are you using surface temperature as your control point?

[Chip]

Feb 4, 2019 15:25:02 GMT -5 jacobk said:

Thanks a lot Ben. I actually already installed a probe like that, but I am experiencing some oscillations in the first part of the roasting - So I thought it would be nice with a second probe to "validate the results. But it makes sense that the drum affects the reading.

You will get variations in the Behmor due to the programming.  I have also mounted this probe and and overall average is the best way to track the temp.  Also be aware of first crack and you can track the temperature/time by listening carefully to the popping/cracking and when it starts and then when it seems to be coming to an end/slowing down.

[jacobk]

Thanks for the answers and advise to you all!

Sebastian. Maybe I’ve misunderstood the definition of bean surface temp. Thought that it was the temp reading you could measure with a probe placed inside the bean mass?

[Sebastian]

That sounds more like an average bean internal temperature (which is much more useful) vs the surface temperature of a bean (which is what an IR gun will give you)

[etalococh]

Feb 13, 2019 13:45:43 GMT -5 Sebastian said:

That sounds more like an average bean internal temperature (which is much more useful) vs the surface temperature of a bean (which is what an IR gun will give you)

You suggest sticking a thermometer into a bean when needing to test temp?

[jacobk]

Makes totally sense Sebastian - thanks.
Yes - you can drill a whole into the side of the Behmor and into the drum. The alchemist has a YouTube video that shows you how.

[Sebastian]

Mar 1, 2019 19:47:45 GMT -5 etalococh said:

Feb 13, 2019 13:45:43 GMT -5 Sebastian said:

That sounds more like an average bean internal temperature (which is much more useful) vs the surface temperature of a bean (which is what an IR gun will give you)

You suggest sticking a thermometer into a bean when needing to test temp?

I'd suggest filling a thermos with roasted beans, drilling a hole in the cap of the thermos, and inserting a stick thermometer. That's a much more precise method of temperature control than an external surface reading.

[rfdk]

You could try to mount this if you don’t want to drill a hole in the oven. meater.com/

[krizzstroganof]

Has anyone tried the meater probe rfdk is talking abou?

[lyndon]

The FAQ for that probe says it can only withstand temperatures of 100C unfortunately. Great idea though if it could handle the higher temps required. I wonder if you could throw the whole thing in the bean drum, accept that the internal probe thermometer will fry, and simply use the external temperature probe as the bean data. Expensive test though if frying one breaks the whole thing.

[krizzstroganof]

yeah, I saw that information too. I was looking at other thermometers just like it, they all seems to only withstand 100C. I hoped maybe someone though of a way to get pass that...