Hi,
the ESS can read MPGs and linear scales no trouble. The ESS reports an integer number back to Mach and Mach decodes that number to display a position in
a register which can in turn be displayed in a DRO.
To do as you wish you would de-power or disable the steppers so they were not locked and then use manual wheels. There will be a delay between the linear scale
and the DRO, approximately the cycle time of the ESS, which is by default 40Hz, or a worse case delay of about 25ms. I doubt you would notice it.
A number of people have tried using Mach to drive the machine, but rather than the DROs displaying where Mach 'thinks' the machine they use linear scales
to drive the DROs. The delay in that circumstance is noticable and objectionable. The only time when the DROs are accurate is when the machine is stopped
and the linear scale/ESS/BoB/Mach delay catches up. The general feeling is that its not the right way to go.
The delay would however totally screw any attempt to use it to drive a closed loop, for which the delays would have to be a few microseconds max.
To do this you would need at least six spare inputs on the BoB/ESS combination, 2 inputs (A & B) per axis. Do you have spare inputs, or are you prepared to buy another
BoB to do so?
Craig