Andy Pugh wrote: > Thinking about this some more, I think it is a quadrature LVDT. > As we discussed on IRC it is a lot like an LVDT with multiple > armatures. The thing is, if you only have that then you can't infer > direction. By having two offset read-heads in quadrature you can tell > direction. > Well, a classic LVDT is a non-repeating position measuring device.
The Farrand Inductosyn can be run like this, but the difference is that the pattern of exciting windings repeats periodically. The Inductosyn has no pole teeth, and the long scale has a continuous zig zag of traces on a ceramic or PCB substrate. Obviously, the scale has low resistance and inductance, therefore it requires a lot of drive current. The pick-up sensor is usually a short length of identical zig zags, with the sin and cos sensor 90 degrees out of phase relative to the long scale. The GE and other sensors were made to offer a similar device but get around the Farrand patents, which were quite well written and precluded any closely similar scheme. Having slots and no coils on the long scale was different enough to not infringe on Farrand. These could be made with 3 coils, and the variation of magnetic coupling between the teeth and the coils changes the amount of excitation that gets to the sense coils. I don't know how you do this with only 2 coils, and it probably restricts the excitation and sense circuits quite a bit. Jon ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
