Grounding operator panels

What could be the bad effect if touch panels are not connected to ground (only + and 0 voltage are attached). I can believe that the influence is poor for a small configuration, but on a bus system with a lot of connected slaves?

Thanks

If you are using RS-232 for your communications, it could be fatal to the PLC and the HMI since RS-232 is a ground referenced signal.

In this case, the panel will try to derive it's ground from the PLC through the communications wire. If the panel ground reference is not close to the PLC ground reference, it can and will cause the com ports to die from too much impedence.

Panel manufacturers put ground points on the HMI's because they are needed to make sure that communications lines are balanced and so that any noise has a dissipation path.

Isn´t the 0V of the PS connected to Ground???

nonuke said:

Isn´t the 0V of the PS connected to Ground???

Click to expand...

No, there is no reason or rule (in the US) that mandates the negative voltage (or 0 volts) be grounded. I have plenty of machines that float the 24 VDC with no problems at all.

I always ground all my 0V and Never had a problem.

This way all the control panels and Power Supplies in the network are ref. to the same point (ground).