Using a 7i95T for 3 axis + handwheels

Hello all... I am looking at retrofitting a Prototrak DPMV5 mill, its supposed to have electronic handwheels as well as full CNC mode.
I am making new electronic handwheels- instead of using the 100ppr units you can get cheap, i want to use a 1024ppr encoder and custom made wheels. Bringing me to the main question: Can i use the 7i95T Mesa boards 4,5,6th axis encoder inputs as MPGs? Arguably with real good encoder counts? Or am i limited to using the 8 inputs as MPGs for the normal 100ppr units?
The machine I have is electrically stripped, so imagination is the limitation (okay maybe wallet too).

ps: I have retrofit a VMC and converted a manual lathe to CNC using 360ppr encoders on the handwheels to make a similar manual/cnc mode. Sometimes it misses counts when i spin fast using a 7i76e MPG inputs.

Thanks!
 

Yes, you can use spare encoder inputs as MPG interfaces.

Note that with high resolution encoders, you lose the 1 count
per detent feature of 100 PPR MPGs.

I have never run this sort of mill- it originally had 3 handwheels, one for each axis, i dont know the resolution of them, but i doubt they were 100ppr, im thinking more like 200-500 to do half thou or 2 tenth motion(assuming 1 rotation was .1"), at least thats what would make sense for me.

i have another question: can a 3rd mpg encoder be added to the firmware of a 7i76e?

Also thanks a lot for the help, and this forum. amazing place!

Its not easy to add a 3rd MPG to a 7I76E/7I76EU isolated I/O
But it would be easy to add 3 or 4 to the parallel expansion port
of a 7I76E,7I76EU,7I96,7I96S,7I95,7I95T etc as long as the MPG
just has 5V signals

Another easy way to add 4 MPG inputs to almost any card and simplify cabling
is to add a 7I73

 

The distance a 100 ppr encoder moves per step is determined by the scaling in hal. So it can do whatever accuracy you want
There is a good example in the docs
linuxcnc.org/docs/stable/html/examples/mpg.html
Easy to use on Mesa, 
Use a Mux8 instead of mux4 to get up to 8 scaling steps...
 

I do understand you can vary the scaling of the ppr->movement, the machine im retrofitting never had any scale switch, though never using this machine originally, i dont know exactly how it functioned. It is a good idea though. Thanks!

To PCW: I would use 5v encoders... are the parallel expansion ports capable of high speed encoders? like 1um linear scales?
7i73 looks like a nice option as well.
Thanks!

Better to use the on card 7I95T encoders for machine feedback.
You can put high speed encoders on the expansion ports
but for feedback use its better to use differential signaling
and the 7I95T already has 6 encoder input designed for this.