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I like that. Great idea. I have no idea if I can so I see the DRO coming to bits shortly.

Impedances? The most horrible thing I have had to do recently was to try to explain the Smith Chart display on a cheap VNA (aka  network analyser) to an older radio ham who could just about manage that 50 and 75 are different. It scanned the range of frequencies you gave it as about twenty discrete points and then interpolated a line in between. Great for almost all real problems on a 3" display but if you set in to scan from DC to the speed of light on a piece of wire hanging down the garden you get a bunch of virtually random points with straight lines criss-crossing the display. Very pretty but...

That said I use a nanoVNA to match my piece of wire hanging down the garden.

Looong thread about lathe macros here
forum.linuxcnc.org/41-guis/26550-lathe-macros

Are the encoder outputs differential or single ended?
If differential, i would use one output for whatever it is being used now and the other to Mesa 7i95T.
Be aware that everything connected that way must have the same 0/gnd/be on the same potential.
I have one such system in use for exactly two years!

nigelh wrote:

However being a bit of an electronic engineer (retired industrial physicist) I worry about loads and impedences.
The 7i95t manual section on the high speed encoders ofers me:
   DIFFERENTIAL MODE IMPEDANCE the min=118 max=122 Ohms
and I'm perplexed. I suspect I am thinking of something different.

Have you ever tried to explain to an inexperienced electronic guy, how the old antena cable (RG58) was 75 Ohm, and the security camera cable (RG59) was/is 50 Ohm?
I've gotten some very strange looks when i tried that... It all seems like black magic to them, till they dig deeper into the subject.