Help terminating cables

[Murphy625]

Can someone provide me with a photo of thier way of terminating sheilded cables?

Im running into noise problems and another thread suggested my pigtails were bad..

How else to get the wires into a terminal strip??

Thanks,
Murphy

 

[akselj]

The corrrect way to EMC terminate the schield is to connect it to ground by a clamp covering as much of the circumference as possible, it can be metal cable cleats screwed into the chassis plate.

On motors and in control cabinets EMC glands as shown in this link can be used.

http://www.rsonline.dk/cgi-bin/bv/b...o=2647336&prmstocknum=2647336&prodoid=1940291

Greetings Aksel

 

[ScottI2R]

Are you terminating shields at both ends of the cable? This is a bonified way of introducing ground loop noise issues.
Scott

In a hundred years, it isn't going to matter anyway.

 

[MikeHalloran]

The German link seems to be verboten.

This page explains why everyone is right:

http://www.7ms.com/enr/free/sample/issue/notebook.html

Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[akselj]

I did`nt try my link to RS-Parts (danish not german) but it refers to EMC glands.

My normal procedure is to terminate both ends of the cable in motor and control installations, the same method as described in the link from Mike Halloran.

"Cable shielding needs to be handled differently for different needs.

Low frequency high impedance circuit shields are best handled by a single point ground (usually, you can ground at either end, but there are cases where the ground works better at one end than at the other). The termination can be pigtailed without adverse consequences.

Low frequency low impedance circuit shields (such as motor drives) are best handled by grounding at both ends. The termination can usually be pigtailed, but we advise against long, indirect pigtails – they may carry currents and associated magnetic fields.

High frequency circuit shields (longer than 1/20 wavelength) are best handled by grounding at both ends. Pigtails are to be avoided – circumferential termination is best.

Multiple shields can be used to achieve the best of both worlds.

If you are working in the field, don’t be afraid to try some alternate grounding techniques – sometimes conventional logic doesn’t apply."

I agree very much with the last sentence.

Once I had problems with noice from a frequency converter, my temperatuer reading changed 15 degrees centigrade when the motor was running, everything was screened as good as possible, the solution was to use a PT100 element without screen, After much "deep" thinking i came to the conclution that I understood nothing ;-)