The FrogPad
A forum to get help or talk about Roastmaster…or anything else coffee.

Probe offsets  (Read 1966 times)


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I have a couple ideas about probe offsets I want to run by you -

1) I am finding that while my roaster allows for a pretty wide range of loads - so far from 250g to 1.5kg - my probe gets a little different mix of beans and air at the different loads so my readings are different for First Crack start/stop etc.  I am trying to set up profiles for the various load sizes and it would be nice to be able to define multiple probes for the same Phidget port based on the load profile and give them different offsets so that the bean temps would read closer to the same temps.

2) I see that Artisan allows the offset to be described in a formula - wondering if that might allow for an offset formula that is proportional to the reading temp so that it could adjust across the temperature range - This was not my idea, it came up on a Home-Barista forum post and I thought you might want to consider it.

You are getting a fair amount of exposure on Home-Barista's Roast and Learn threads by the way :-)

Danny Hall

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1) Hmmm... probes are defined at the app level, in other words, they don't exist in a database, so making strict connections between a curve and a particular probe isn't easy in the current configuration. That's actually the reason I only allow 1 matching definition at a time, so that curves can easily locate their probe when needed. Not to say that couldn't change, but that was a design choice so folks wouldn't have to define and calibrate multiple probes for different databases. I wonder if a modifier in the curve binding might be a better choice here. If defining multiple probes with different calibrations would fit the bill, maybe a simple numerical modifier like "Calibration Modifier: 0.9" would work equally well. Essentially, it seems to be the same difference, and achieve the same effect with less work on the user's part, avoiding the process of defining and managing multiple probes. Any thoughts you have are definitely welcome.

2) Yes, actually, I've thought about this. My thinking was the ability to define points similar to nodes on a curve. Since probes have different tolerances at different temps, maybe provide the ability to enter multiple calibration points, say 0° C: 0 offset, 140° C: 10 offset, 200° C: 15 offset. Roastmaster could then interpolate the value based on that information. I really like that idea.

Thanks for the thoughts - I'll have to check out Home-Barista. I've been so head deep in code trying to be ready for iOS8, I haven't looked up from my computer for a while. :)