Thank you Arturo.  I will check to see if I have the inputs configured as pull down.

I changed the sampling to 0.001 seconds (the lowest setting it allows) and I see the spindle speed in Diagnostics.  The spindlw speed is steady up to about 800 RPM and then it starts jumping all over the place, increasing to as high as 6000 RPM at times.

I reviewed all the settings again and I see on the ESS Configuration screen Spindle tab that it says I need to assign some output pins. I don't know what pins to assign to that.  the only outputs I have are for the motor drivers.

I am not able to insert images but I am attaching images of the Spindle Tab and the Output Signal tabs.

I did some reading.  my encoder has a resolution of 2000 PPR.
I wonder if that is too high and it is overwhelming the ESS at higher speeds?
I am going to try changing the prescaling and effective PPR to 40 and 50 respectively.
Thoughts.  See the attachment for my Spindle tab in ESS config.

I see what you are saying, but it is not clear to me exactly what is the problem you are having.

Mach4 reports the spindle speed if the spindle is running slowly, but as soon as it gets up to about 800 RPM the reported speed is all over the place, going as high as 6000 RPM.  I thought maybe it was the prescaling, but that is a guess.
To be honest, this may be a question for Warp9 since the spindle is connected (indirectly) to an ESS.

The ESS can read the encoder crazy fast.  Please tell me more:
- What breakout board are you using?  Make sure it can handle the pulse rated.
- Check the ESS kernel speed.  Make sure to set it to run fast enough.
- You may be able to set the encoder output to a resolution that works better.  For reading the spindle position 500 should be good enough. Maybe less would also work.

Arturo Duncan
https://cnc4pc.com

I am using a C10 BOB on port 2 of the ESS.  The C10 is configured to use 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 15 as inputs.

That is good.  Here are some thoughts:
- Please comment on what I said about the ESS speed.
- Test this at different speeds and monitor the encoder position in the ESS diagnostics, understand at what speed you lose it.
- Maybe the encoder signals are weak.  Maybe the C72 may help you buffer the signals: https://cnc4pc.com/c72-differential-line-driver.html
- We do have a board that is specially designed for this, but may be a overkill for your application: https://cnc4pc.com/ess-third-expansion-board-enco.html

I can't find a setting for Kernel Speed.  Was that a Mach3 setting, what I found online seems to suggest that was a Mach3 setting and is not configurable in Mach4.
Attached are screenshots of the ESS and Control tabs.

Here it is.  Play with that value.

The Omron E6B2-CWZ1X encoder used has a differential line driver output so the C72 board is not needed. It would simply duplicate what the encoder already does. However the encoder is now being used as a single ended output device. To take full advantage of the differential feature a C46 - Differential to Single Ended Converter could be installed close to the C10 BOB board. That way the transmission would use the more noise resistant differential mode for most of the path.
https://cnc4pc.com/c46-differential-ended-converter.html
You would also need a ethernet cable and an rj45 breakout adapter like this at the encoder end.
https://www.amazon.com/jujinglobal-Breakout-Board-3-81mm-Terminal/dp/B09K41TPQL/
The breakout adapter could be skipped if you have the skill to cut the cable, identify the wires and connect directly to the encoder.
This modification would only be a benefit if you actually are having a noise problem so it should probably be your last resort.