You currently see different things in RT3 compared to R.W. RT3 displays both P-RoR (the RoR for the bean probe) and I-RoR (the RoR of the IR sensor that’s central to the IBTS). Currently R.W displays only P-RoR. R.W will eventually display both P-RoR and I-RoR but it isn’t available yet
RT3 uses fixed scaling of both Y axes. And yes the graph of I-RoR will shoot off the chart initially. I-RoR has a huge swing initially because the slope of the IBTS curve is so steep. It’s possible to change the scaling of the Y2-axis (the one on the right side) in RT3’s Config settings to something like 120 to 160 (it may require an even higher value) to keep it visible, but that makes reading RoR later in the roast of little value as it would hug the X-axis…
Most of us have chosen a Y2-axis setting that keeps P-RoR useful for the whole roast and requires waiting till I-RoR comes back into view to be able to use it. I set Y2 = 40 but I’ve seen charts that look pretty readable with Y2 = 60 or even = 35. You can experiment with the Y2 setting with completed roasts by setting the Config values, saving them, then looking at the chart. Nothing changes in the saved data… the Config setting just determines how the graph is drawn by RT3.
The reason IBTS sees that huge swing is that initially IBTS is used to set drum temp during preheat. The sensor is aimed at the interior surface of the drum and that’s all it sees… temperature only varies as a result of the structural pieces of steel that move past the view port. If you preheat to 410°F, that’s the nominal value that the IBTS graph displays. When you charge the drum, beans that are at room ambient of say 75°F suddenly pass thru the field of view of the IR sensor. So the sensor output suddenly drops from a measured 410°F to something a little more than 75°F - a change of about 325F°. Curve smoothing limits that swing but if raw data were being plotted, that first reading would be -325. Actually negative values aren’t plotted but very shortly after the giant negative swing the IR temps start rising very fast and you get changes over 100F°. It’s the nature of the thermal activity inside the drum that drives the IBTS output.