Denford Novamill Mach3 conversion

[irving2008]

I think you're being a bit categorical here Irving! You can't rely on a limited slew rate to do the smoothing for you. And your comment on ground referencing isn't helpful because by definition "signal ground" is what the control inputs are referenced to! The question is, can the 0v on the controller be safely connected to the signal reference on the vfd?

John, not categorical but maybe I'll accept I was being too generic. I hadn't read whole thread, but was responding to specific posts. I can rely on VFD not needing external capacitor cos it works for me and many others. Most VFD have internal low pass filters anyway.
And the diagram posted by the OP shows a VFD.

However, it now transpires that's all irrelevant to the OPs requirements.

I agree with Eddy, to show COM as 'chassis' but have it at some unspecified high voltage is wrong in my book.