Re: poor mans digitizing gizmo

If you've seen the digitizer pads that are used on some computers,
they use a signal swept across a fairly coarse (0.1" or so) grid on
both sides of a PC board. (The X axis is on one side Y is on the
other). The pickup coil in the stylus or puck "sees" the signal come
past and the circuitry imterpolates the crossing point.

I don't see how to practically do this on a skin top, BUT there is
another technology that might work and should even be adaptable to
mounting directly on a mill (Therby dragging this message back in the
general vicinity of the topic.)

It uses either three strip microphones or 3 pairs of microphones
arrayed on the X, Y, and Z axis. The stylus makes a noise from a spark
gap or ultrasonic transducer and you measure the time it takes for the
sound to get to the various microphones. The resolution and range is a
function of the counting frequency and the size of the counting register.

This type of digitizer **could** be free-standing or even mounted on a
mill. If you handled the frequencies properly you might even be able
to use it for feedback, although getting to a useful resolution might
be a trick, not to mention the delay involved.

I could certainly see making a digitizer arm using this technology.

Chris