Even after cleaning with alcohol swab ibts temp is lower than bean temp by the end of roast ?
The roasting snot that gets on the IR sensor lens is invisible and resistant to the alcohol… it doesn’t just dissolve but rather softens a little. It takes several applications with some rubbing with the cotton swabs even when you are cleaning it frequently. It sounds like your IBTS has a lot of build-up which could take a lot of work.
Another possibility is a calibration issue with the IBTS and that will take a little dialog with Aillio Support… I don’t recall seeing posts from anyone that has encountered that.
Bruce
thanks
Bruce, with all those coffee snot symptoms, maybe you should get those beans vaccinated. 
Makes me appreciate what my mother put up with when hay fever season started and she had to mop up behind a 4 year old!
Bruce
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Hello,
I have the same problem, it seems to be related to weight of the batch:
I did 5 batches 450g IBTS temp>bean temp
Following 3 batches 1kg IBTS temp<bean temp
Any advise?
Thank you,
Valentin
I believe it’s the nature of the roaster instrumentation. Large batches have a smaller difference between IBTS and BT than small batches do,
However IBTS shouldn’t be less than BT at the end of the roast regardless the batch size. It may well be an indication there are contaminants on the surface of the IR sensor of the IBTS. You can fix that by cleaning the IR sensor lens using cotton swabs wet with alcohol. The contaminants don’t show up on the cotton during cleaning so there’s no feedback about your progress. Trial and error I’m afraid.
Also those contaminants aren’t soluble in alcohol though they do appear to soften. Until Aillio or the sensor mfr finds something else that’s safe, the best we can do is soften it and clear it off with the swab.
Bruce
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I have noticed that a dirty IBTS reads lower while a dirty Bean Probe reads higher. A cleaning cycle with both sensors cleaned gets the temperature readings back to normal.
My bean probe gets a thin right brown film after every 10/12 Kgs and needs a gentle scrub with a piece of cloth dipped in isopropyl alcohol every time I do a faceplate clean up. The IBTS not so often, but I do make it a point to see if it is dirty and blocked when ever I open the faceplate.
You could try wiping clean the bean probe once. It takes on a light brown sheen over time and reads hotter than normal.