What do the calibration numbers mean?

  • Using firmware 1.21rc1, P3 rotating magnet sensor, with very conservative jerk, acceleration, speed I get calibration numbers like:

    measured sensitivity 26.29mm/rev, measured minimum 3%, maximum 6% over 6

    let me refer to these as:

    measured sensitivity Amm/rev, measured minimum B%, maximum C% over 6

    (note I am using a different hobbed measurement wheel from the one in the kit, hope to get some photos up tomorrow, so A probably not the normal value)

    (1) I find that A tends to get smaller as the calibration runs longer. Is this assymptotically approaching the correct value or just moving within the error range? Also A is larger when I use higher jerk, acceleration, etc.

    (2) I'm assuming B and C go into the M591 command as RB:C now, with some leeway added. In runs with higher accelleration etc., I have B=0% and C=5%. So does adding leeway mean B goes negative? What would be reasonable numbers to put into M591 given these results (or is B=0% unacceptable?) I realise that I do not actually understand what B,C indicate?

    (3) or perhaps I should not be looking with this as David noted elsewhere that he has not yet tested 1.21rc1 with the rotating magnet sensor?

    Just one more point - this kit (the Duet + accessories) is absolutely brilliant and I am loving it!


  • administrators

    Yes I think there is a firmware bug. The min and max values should be more like 80% and 120%.

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