DRO runs away when I turn on motor

[Zoltan]

So, I'm not sure where to start troubleshooting this, aside from swapping out the DRO entirely.

This is on my lathe. Whenever I turn the motor on, the Z axis DRO readout starts rapidly increasing. I'm using the original iGaging linear scales, with shorter and shielded cables. The lathe uses a KB Electronics PWM. 

Here's a video of it in action:
https://youtu.be/Oc5jP8JfYJQ

Any ideas what's going on and what to look at first?

[gerritv]

A couple of things to try:
1. Power the scale interface from a different plug, e.g. across the room.
2. Make sure there is no oil etc. on the Z scale.
3. Electrically isolate the Z scale from the frame of the lathe

I have a KC1022 with KBCC-125R. The only problem so far was cutting oil on the Z axis scale giving problems. I sealed the cover better to avoid that in future.

[Briney Eye]

So, I'm not sure where to start troubleshooting this, aside from swapping out the DRO entirely.

This is on my lathe. Whenever I turn the motor on, the Z axis DRO readout starts rapidly increasing. I'm using the original iGaging linear scales, with shorter and shielded cables. The lathe uses a KB Electronics PWM. 

Here's a video of it in action:
https://youtu.be/Oc5jP8JfYJQ

Any ideas what's going on and what to look at first?

For me, the best solution to noisy/drifting scales was adding power supply decoupling capacitors in the scale read heads.  Transformer-type wall warts can help some, but the decoupling is really the solution.