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Igaging scales hysteresis
#4
Old issue, but, I had a thought.

I've noticed with the scale unmounted that there is some apparent "elasticity" in the reader head case. In other words, I can press on it in one direction, without the scale actually sliding and the numbers can climb a thou or two until I release pressure. The problem is that these scales have a tight felt wiper at either end of the case slot. These apply enough pressure to the scale that sliding is prevented until enough pressure is applied. Together, these two characteristics mean that the head may feel "pressure" without sliding, and that this pressure will affect the reading by a few thou.

When mounted, a head stops sliding in any direction with residual additional pressure built up at that position. As you reverse the travel the pressure is first reduced in the primary direction, then increased in the secondary direction, before the scale actually slides. This will show up as non-linear positioning at the reversal -- something akin to backlash.

So, as a guess, it might help to lubricate the slide, so that the head slides more easily with the carriage movement.
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Messages In This Thread
Igaging scales hysteresis - by leeko - 05-26-2017, 02:18 AM
RE: Igaging scales hysteresis - by Ralphxyz - 05-27-2017, 09:52 PM
RE: Igaging scales hysteresis - by leeko - 05-27-2017, 10:40 PM
RE: Igaging scales hysteresis - by Steve - 05-27-2018, 11:32 PM

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