Following error 6I25 - 7I77

There is a possibility of noise causing missed counts. There is a long standing firmware bug with muxed encoders with the filter off. "filter-off" mode is supposed to still have a 3 sample digital filter enabled but due to a mux sampling bug, a shorter pulse can be passed through the filter. I will make up fixed firmware sometime today if you wish to see if this helps.

I also looked carefully at the maximum count rates:

5I25 --> muxed encoder filter on ~ 550 KHz
5I25 --> muxed encoder filter off ~2.7 MHz

These assume perfect quadrature, if you allow 50% distortion in the encoders A, and B pulse symmetry (duty cycle) you must divide these count frequencies by 1/2.

A to B or B to A phase errors of 45 degrees (50%) will also limit the maximum count rate to about 2 MHz in either filter mode due to the ~4 MHz input sampling rate of muxed encoders.

OK

Im running indramat eco drives in all axes.
Most of my motors has multi turn resolvers, 2 motors in nikken has pulse encoders.

Drives them self use encoders/resolvers and also dual feedback is supported.
Those are capable of different operation modes like positioning, velocity, torque.
Im using them in velocity mode.

Drives emulate incremental or SSI encoder signal to output for cnc and are capable to 1MHz pulse rate output.
Interface is RS422 differential and 7I77 is configured to differential inputs and each line have 120 ohm resistor integrated in 7I77.

I made new wiring to help issue, no change in behavior.
Now every encoder line is shielded individually.

7i77 is configured for SW mode3, This is cause i need 5Vdc handwheel support. For all encoder channel filtering is enabled.

At the moment Im running 2000 pulses per rev incremental encoder output from drives.

I was testing this yesterday and found that 15000mm/min (ballscrew lead 10mm/rev) speed to be maximum where pulses where not lost.

2000puls/rev * (1500rpm/60) * 4 = 200000 Hz

At the moment Im limited to 200 kHz.

I think I should get better count rate than this....

Yeah, as I mentioned you should get to ~550 KHz even with the filter on
I suspect you will need to look at your signals with a oscilloscope.

Just as a test, does the maximum rate change if you enable the filter?
Have you changed the default encoder sample frequency?

Hello

I was wrong, my encoder count per 1 reolution vas 5000.
so it equals 500000hz at 1500rpm.

What you said was upper limit.

I included encoder capture from 15000mm/min.
This shows A and B lines.

it does show some resonation in B line.

edit:
Resonation was from my scope, channel b needed ground as well.
So no error or interference on encoder signals.

I can manage with 15000mm/min feeds.
Best thing about this is that i know what is causing this problem.
Now i can avoid it and run some long 5-axis paths without worry.

So you have the encoder filter enabled?

You should be able to get to more the 2 MHz with the filter off

Ok I will try that too.

But 15000mm/min is ok for my home use.
I will try with filter off, then i could get pit more accuracy for machine (increase encoder count pit more).