Re: [CAD_CAM_EDM_DRO] Re: Insulating D-shell from chassis?

Hi tom;

I have to respectfully disagree, ground loops can be a problem in
industrial controls. That is not to say that the originaly poster
might not have another issue, which is one of the reasons I mentioned
that attempting to eliminate sources of noise at the source is a good
thing to do.

The other thing that one runs into with industrial systems is ground
offsets, many an RS232 port has been fried when plugged into a machine
with a slightly differrent ground potential. Reactive circuits that
shift the current phase seem to be a big cause of this sort of issue.

While it is difficult to diagnose the issue clear across the country, I
do know that ground loops show up in the type of installations
described. One could argue that a few optical isolators might take
care of the issue, but I won't go there simply because I only have
passing knowledge of the hardware.

Thanks
Dave


mayfieldtm wrote:

>I've been reading in these posts for some time now about ground-loop
>problems in logic level interfaces.
>
>This just should not be a problem.
>
>I have a gut feeling that isolating a DB Connector is just masking an
>underling problem that could be a hazard to equipment and user, and
>the stepping problem will come back when least expected and least
>needed.
>
>Gound-Loops are typically only a few millivolts in high impedance
>lines such as line level audio systems. TTL Logic is usually pretty
>clean where improperly designed CMOS Logic Lines could be more
>susceptible.
>
>I would suspect a poor ground or wiring problems somewhere in the AC
>Lines.
>It might be advisable to have an electrician to dig into if and why
>there is such a large potential difference between your CPU and
>Controller Chassis.
>
>Also, Avoid RS232 and Parallel lines that are longer than needed.
>When I need to use RS232 in long or noisy environments, I'll use
>RS232 to RS485 Converter modules on both ends.
>If possible, use the same power outlet for all equipment.
>
>Any engineers out there that can comment on proper line loading for
>long Logic Level Lines?
>
>Tom M.
>
>
>