IBTS waves / wiggles

Has anyone experienced these wiggles in the IBTS (white / gray line in my screenshot)?

I didn’t get them early on, but they’ve been persistent and appear every single roast.

I have seen these same artifacts in data unrelated to roasting coffee and was assured they develop as a result of differences between the sample rate of data collection, rotation speed of what is being measured, and physical configuration of the devices internal components including (in this case) the beans. So what IR is being delivered to the sensor at the instant the sensor is sampled decides what the delivered sample will be. The image the sensor sees varies throughout the roast and throughout each rotation but the image is not homogenous- there are beans falling at a different rate at the end vs the beginning of the roast (related to weight loss) and geometric differences in the internals of the drum construction.

It’s much like what we might have seen in a western movie when they gave us a shot of the stage coach wheel which seemed to be rotating slowly or even backward. We knew which way it was rotating but the artifact created by the frame rate of the camera vs. the rotational speed of the wheel gave us a different visual effect.


If you have a new Bullet, it can happen due to the drum not being completely seasoned.
My Bullet did this for the first few roasts after the initial seasoning roasts.
After ten or so roasts, they should be gone, nothing to worry about.

Makes sense Bruce. I appreciate the anecdotal film reference, too. So maybe not all that dissimilar to the issues we experience with physical probes. Individual, continuous readings will vary based on physical differences at the time of reading, but the general slope is true (thus the use of smoothing). I only expected the infrared to be a bit more consistent than the physical probe. Accurate, but also a more steady reading.

Yeah good idea Warren. I’m about 50 roasts in at least; but I do roast fairly light. I did season it initially.

Exactly! Then those not-very-extreme IBTS swings up and down translate into Toad’s Wild Ride when the f/w computes I-RoR. But the eye is pretty good at picking out what is useful. My take away is that trying to manage a roast based upon instantaneous values only leads to frustration… this is all ‘big picture’ stuff.


I’m totally with you, Bruce. Sometimes I feel like that the RoR numerical reading is not in sync with the RoR chart while I am roasting…

If you haven’t yet, it’s probably worthwhile to try cleaning your IBTS sensor. I’ve seen large drop-outs in the IBTS curve a couple of times that I attributed to a flake of chaff briefly sticking in the viewport. Sorry not very definitive answer.