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BoB_S

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  1. Damian, I'm executing the auto-zero with a one-shot, it is interlocked with function is progress bits, not using filtering/rounding. As for having auto-zero enabled in a static situation - isn't it supposed to work either way ("Once Auto-Zero tracking is activated, it stays active until the function is suspended by the application") ?. Nevertheless, I have recalibrated the system (reminder - currently it is a BARE loadcell), saved calibration, acquired zero, saved calibration again and haven't enabled the auto-zero - shall see in a few hours if we get that dreaded drift again. Joe, I'm using AC exitation mode. The measured voltages were the same for 12g offset (drift) and fresh calibrated zero : E-toE+ = 4.912Vac, SG-toSG+ = 2.7mVac. As per the loadcell (Zemic L6N class C3) datasheet, the recommended exitation voltage is 5-12V. I haven't checked the wiring (done by another person), but I assume it is correct since the loadcell operates fine except for the drift.
  2. Well... Yesterday I left a bare loadcell, calibrated 4 points (0,6,12,24 grams), saved saved the calibration, set the motion band, turned on the auto-zero track. As before, the "system" was stable on 0 for a while, today I find it showing a -7 grams offset. Nobody has touched the loadcell, so there's no hysteresis issue here. Temperature around the loadcell was constant, around 22 C, give or take 1 degree. Maybe the auto-zero doesn't work the way I think it is supposed to ? This is quite frustrating....
  3. Hi Keith (Walkerok), The terperature changes around the device are insignificant. The first point of calibration is zero in my case too (with the platform, of course). If the nature of this drift is indeed mechanical (which is plausible), doesn't the auto zero track FB supposed to counter exactly that ("hysteresis when a container is pressed down on and what level it retunes to") ? Anyway, I'll try to strip the system to the bare loadcell and see what I get.
  4. Hi, The Help file (under Calibration - Calibrating Points clause) states that zero doesn't have to be calibrated. Nevertheless, I have tried different calibration settings, one of the points was 0 as well - the result is the same. Additional suggestions before turning to support ? - Thanks.
  5. Hi All, The loadcell has been calibrated with 4 points (5, 20,50,100 grams) , zero acquired, calibration saved. Motion band has been set (LC Motion Band = 2) The auto-zero-tracking is set to pretty tight definitions: LC time = 1, LC tracking band = 1, tracking range = 1, and activated. Everything works fine for some time - the loadcell output is pretty steady on zero, some minor fluctuations here and there but it seems that the zero correction fires every now and then to correct. However, in a matter of hours, zero begins to drift ( up to some 18 grams), which makes the whole application null and void. Same happens in both excitation modes, btw - in DC mode zero drifts up (+), in AC mode zero drifts down (-). Theres no litter buildup on the platform, no significant temperature fluctuation around the loadcell, not much mechanical movement - the construction is quite solid. What am I missing here ?
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