If it's all you can get then fair do's, Sherline have a system that counts the handwheels, but it acknowledges the shortcomings of this, allowing you to program an axis offset. and it reads it all from one "readout" hence the name.
Glass scales, with an independent readout are normally considered the ideal. I use the system sold by arc.
If you want one on the cheap, I believe you can get some magnetic, Vernier type scales with a little readout unit from machinedro. This would also take into account the backlash of the slide. But they probably wouldn't last as long, as well as the batteries to contend with of course.
Michael W
Edited By Michael-w on 27/08/2017 23:53:57