IBTS vs Bean Temp and ROR on RT2

I welcome some clarification on the following:

  1. IBTS < Bean Temp: On my Bullet the IBTS is consistently less than the Bean Temp throughout the roast - what are the common explanations for the temp differences ?
  2. ROR in RT2: In the Roast time software is the ROR I see based on the IBTS or the Bean Temp
  3. Why do we need to see both IBTS and Bean team if IBTS is considered to be more accurate?

thanks much

Aillio needs to answer here but in the interim here’s my take on your 3 questions-

1- If IBTS < Bean Temp, odds are very good the IR sensor of the IBTS is dirty. If you look at the sensor with a fiber-optics probe you (probably) won’t see anything on the IR sensor lens, but cleaning the lens with a cotton swab moistened with alcohol (several times!) will improve or eliminate the error. If you roast dark, IBTS will probably collapse down toward Bean Temp after 1C but shouldn’t cross below.

2- Currently RoR is based on Bean Temp only, though I understand the IBTS-based version will be coming at some point. The issue is artifacts in IBTS data (from IR sensor sample rate vs. bean and drum movement) that cause the data to move around a lot. Since RoR represents the change in temp data vs. time, Bean Temp-based RoR will be more readable than RoR based upon IBTS… at least at this point.

3- Bean Temp is thermocouple-based. Thermocouples have been around a very long time and generally are durable and repeatable within their usable range. But their response is slow because of thermal mass of the thermocouple, the mass of the probe case and the surrounding metal that has to be heated. On the other hand, the IR data from IBTS contains artifacts that make reading it a challenge. And then there’s the issue of IR calibration errors from surface contamination on the lens interfering with IR emissions (1- above).


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  1. Depends on which type of Bullet you have. If you have the V1.5 or V2 then the IBTS would normally be higher. Please share a profile so we can see the graph.
  2. ROR is based on bean probe for now.
  3. We don’t but include it so all Bullets have this in common. Some people still use it and new Bullet users coming from another roaster is used to seeing that kind of info. Internally it serves as an extra safety probe.

Thank you for the thoughtful and informative comments! As I looked closer at the display and the RT profile, I realize I had inverted the 2 temperatures and the IBTS is > Bean probe usually 11-16ish degree C difference depending on where i am along the roast curve

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As mentioned to @bab I have inadvertently inverted the temps on RT profile, and also got a bit confused on whether the bean temp on the Bullet itself when I press the “bean temp” button is the IBTS or the Bean Temp - the only difference is the little red indicator light above the button. It would be awesome if the indicator light changed colour depending on whether you are looking at IBTS or bean temp. this would be helpful for those of us who sometimes ‘freestyle’ it and don’t use the RT software or connect to any computer.

As I understand light on = IBTS, light off thermocouple is being used