Nano 7 probe temp Vs bean temp & environment temp on other roasters

[mr. bean]

Hi Peoples - especially Wayne and Chris!

Can you help me understand a bit more the relationship between the Nano 7 probe temp, and the environment temp Vs bean temp that you see in other roasters data logging?
Eg. this simple diagram from Scott Rao's website (article on crashing ROR's and baking):

not+baked.png (78.59 KiB) Viewed 4291 times

I know you say the sensitivity of the probe and the placement means it's supposed to be closer to actual bean temp than some roaster's probes.
But surely there's still a sense in which we're reading (and driving!) environmental temp rather than bean temp, especially early on.
The main reason I ask is that if you look at the example above (and most other graph's I've seen from other roasters, whether drum or air), they go hard with environmental temp early on to create high difference between inner and outer bean temp, which is important for development (I think!).
So should we be driving higher temps early on and letting the bean 'catch up'? Or would that genuinely be driving bean temp too high too fast?

[mr. bean]

Further to this... has anyone done much testing with an IR Thermometer?
I think it would be interesting to compare the bean surface temp according to IR with the probe temp recordings.
I did some very basic, not super well controlled test the other day using an old IR thermometer I have (but it's a 1:1 scale thermometer, so had to stick it down the funnel using a pair of BBQ tongs to hold the button down!).
Keen to get a better thermometer and do some more testing. According to my (not very tightly controlled) testing, here's the result:

Screen Shot 2021-05-06 at 8.47.04 pm.png (199.95 KiB) Viewed 4199 times

The red line is the probe temp, and the blue line is my IR temp measurements (with smoothing)

Basically the probe and IR bean surface temp were identical at first, then widened from 5deg gap to about 25deg gap from 30sec through to 3mins. Gap increased much slower till around 6mins, when gap started widening again.
From memory, FC happened around 176 IR temp. I've read we should expect it to be more like 196 bean temp??
I wonder if that means the IR temp readings are not really accurately reflecting bean temp?

Thoughts?

[fnq]

I think the problem with I R temp or other probes is finding a spot that reads consistently in the first instance and accurately if possible ( 176 vs 196 degree variance example above.) due to the relatively small size and turbulent environment in the KL the fluid zone/tumble zone are pretty narrow. I think the KL software fairies do a pretty good job of taking the probe temp info and making predictive analysis of what is actually occurring at the bean - this relationship between bean temp and probe temp as well as what i will inexpertly call thermal momentum is not a simple one - or at least not for me!!!!!

It would be interesting to hear from some drum roasters using the KL as a sample batch machine..... for example how a KL 8 minute 30 second roast translates to a 14 minute drum roast - in terms of usability of data.
I would guess the phase percentages, ROR and Development Time ratios would be transferable but the ways and means of getting there in a drum roaster would vary a lot compared to the KL roaster - total uneducated guesswork there , so no idea really.

Good luck with your experiments and sorry i couldn't add anything really useful . cheers Darryl

[mr. bean]

Thanks Darryl.
I’m guessing the reality is that actual bean temp is somewhere between IR and the probe.
Kaffelogic have stated that the probe is a mix of environment and bean temp. I’m not sure whether there’s algorithms adjust what’s actually measured to ‘guess’ the real bean temp and display that?

I suppose my real question is which temp line does the Nano probe temp more closely correlate to compared with the above example from a typical roaster?
Or is it half way between??

[il_guru]

I wanted to post a temp related question, but I think this may relate to this topic.
I was wondering if batch size may affect the temperature measurment and so the profile curve i should use: I means, is there any sensitive difference in reading and actual temperature between 120g and 100g batch size?

I usually use 100g batch, but a couple of days ago i had to finish a green batch and so i did two 120g batches: during one of them i heard a first crack (a couple of sound) at the "real" 196°C temperature while usually my first crack temp is around 206°C (at 5:15 if this can be a useful information) . Maybe it was just casual, because a lot of crack started popping at 206, and with the other 120g batch i had no FC at 196°C.

[fnq]

in reply to Mr bean ... But which temp does it closest resemble etc

The problem is that the answer is it varies ( thus the predictive algorithms and time delay/advancement for the afterburners(pun) to be switched on and off... (eg if you want the profile to go around a curve and Follow it, you set the power change say 10 seconds before the predicted bend) in my eyeballing of the profiles i use most, the Bean temp vs probe temp offset is approx 14 degrees at FC (196 bean temp shows 210 probe temp) but at second crack the offset can be almost nil 224 bean temp and probe temp 225 -230)


Hi il Guru. I use 100gms (within a few gms) ALWAYS. I have found the fluidisation easier to control at the 100gm point by varying the fan speed calibration if required. At 120 gms i found more inconsistency in the roasts- which i put down to not enough air speed heat all the way through the batch all the time. I could probably try to do the recalibrate thing on the larger batch sizes but i found it easier to get repeatable results just by limiting roasts to near 100gms.

My logging of FC is maybe closer to rolling first crack - as i believe the KL paperwork suggests wait until you hear 3 pops in a second - i have quite a few roasts with some outlying FC pops ( especially those less well size graded beans) but I ignore until 2 or three FC pops in quick succession. Funnily enough the bottom of the bag batch is probably where more of these outlier beans will be found - so your 196 FC could just be smaller beans.

Cheers Darryl

[mr. bean]

Hi Darryl, What are you measuring BT with to compare with the probe? an IR Thermometer? I didn't find the temps converging towards 2nd C myself...

Il Guru, I would agree with Darryl that you just had some early pops. I get them occasionally.
I regularly roast 120g, but I have tweaked fan profiles to start at 1550 and drop over the first 30sec to match the standard fan profile. I just found too many large or dense beans were not getting moving well enough otherwise. After that first 30sec or so I haven't noticed any problem with agitation even with 120g.

I also often roast 100 or 110, but can't say with great confidence that there is no difference in how the profile behaves. I'm pretty confident that first crack is still around the 206 mark though, regardless of size, so must be behaving fairly similar.

[fnq]

Hi Mr Bean

What am i measuring Bean temp with.........?????

nothing actually, i am using the collective wisdom of others, ( and of course google)

The general consensus is the arabica beans achieve FC at a known temp of 196 degrees ( I typed this into google arabica bean First crack temp) similarly second crack is 224 degrees.

So i am using these as known points..... no matter what my probe temp is reading when FC occurs i know the bean temp to be 196.

Second crack is a bit more of a guesstimate for me....Wayne suggests second crack is at a DTR of 34- 36 % , so check your temps at this point....... I ended up moving away from anything over 4.5 Roast level , as i was getting ashy tastes AND i ended up not caring if i way aty second crack or not so long as the coffee tasted good


This post by Wayne and this thread in general may be of help

https://kaffelogic.com/community/viewto ... rack#p1372

[il_guru]

Thansk both for the answers (and sorry for my delay).
It was the last batch for that coffee so probably it was due to some smaller bean dropped to the bottom of the sack...
I think i will need to play a little with the fan, because i create a good light profile (to my taste, but i will share it to the comunity to have some feedback) but some beans gave me some inconsistency in terms of colour. I tried to change fan calibration but the result was similar, so i will probably try to do something like what MrBean suggested in the first steps. But before goind to deep, i think this may be due mainly to too different bean size: i toasted two new coffee yesterday (my first South american!) and the results were more uniform.