Linear scale resolution vs axis speed

Hello,

I'm wondering around getting a Ditron glass scale, but there are different resolutions available: 0.1, 0.5, 1, 5 um.
MESA 7I95 which is my current playground has encoder count speed of 3Mhz as the manual says.

If the scale is set up in closed loop feedback with a motor, does it's resolution effectively limit axis movement speed?
3Mhz with 0.1 um gives 100 mm/s, then 500, 1000 and 5000mm/s with larger resolutions.
Is this correct thinking, if the speed is not limited by servo encoder or 10Mhz MESA stepping speed?

If on the other hand the scale is used as a mere readout, connected to MESA encoder input, what happens when axis speed exceeds counting capabilities, does it return wrong position?

Thanks for any insights
 

Check the 1)linear scale/encoder spec 2)machine speed limitations
For 1um linear scale say rated max working speed is 60m/min
which is 1m/sec or 1000000 counts/sec .
As it is a quadrature count of A/B,each channel is max 250Khz at 60m/min which is linear scale limit. Going with 0.1 Resolution may give higher resolution count for position resolution but may not gain any servo loop advantages .
1um resolution linear scale is more than enough for any machining application.

Perfectly logical, thanks.
One meter per second is more than enough.

They claim that resolution is 0.1, 0.5, 5 or 10 um
which looks rather unrealistic. With 0.1 of a micron resolution the rate would be 10 times more (2.5Mhz).
I started counting speeds without thinking the numbers are just wrong.

Do you have experience with these low end scales? Are there any big time gotchas?

Ditron specs from ali

With spec 20um grating pitch you can get 5um TTL resolution without any multiplier.
Anything higher resolution counting needs interpolation multiplier.
For 1um TTL resolution need a 5x multiplier build into the scanner head.
This is common with any brand scale and multiplier exist for every resolution.

Yes I have used Ditron scale for DRO purpose. Not in servo positioning application.
It may just work