All I can find in the meager documentation is that they power up with both counters zero. The docs only list commands to query the counter values or re-zero the counters. Anyone who can find more info would greatly help!
I saw that the doc said that the turn counter was zero, but since the
single-turn zero position can be set via the proprietary windows-based utility
to anywhere, I am assuming that they retain this setting across power cycles
(otherwise having an index position is meaningless)
But doesn’t this keep chain sag in the mix? We want to measure independant of the movement of the chain/sprocket mechanism. I must be missing something here.
I’m looking at them to replace the current encoders, not eliminate chain sag.
it is impossible to eliminate chain sag entirely, no matter how light the string
and how tight you pull it, there is always going to be some sag. We need to
figure out how to model it and account for it in the calculations.
going with very light line may make it so that the sag is small enough that we
can ignore it (we are aiming for an accuracy of 0.4mm, if the worst-case sag is
0.1mm for a line, we can probably safely ignore it), but we would need to prove
that it really is that small (without introducing another, larger error)
someone said a few posts up that stretch only depends on tension, but sag is
more complex. I disagree, both sag and stretch depend on how much tension there
is and how much line is out. The forumla for stretch is simpler, and we have not
yet found the right formula for us to use with sag, but once we find the
formula, it doesn’t matter how messy it is, computers are good at math