(1) Shield earthing
When a shield of the shielded cable is earthed to the cabinet body, please ensure
that the shield contact with the body is over a large surface area. If the cabinet body
is painted it will be necessary to remove paint from the contact area. All fastenings
must be metallic and the shield and earthing contact must be made over the largest
available surface area. If the contact surfaces are too uneven for optimal contact to
be made either use washers to correct for surface inconsistencies or use an
abrasive to level the surfaces. The following diagrams show examples of how to
provide good surface contact of shield earthing by use of a cable clamp.
(a) Peal the cable insulation off and
expose the shield section
The method of earthing by soldering a wire onto the shield section of the
shielded cable as shown below is not recommended. The high frequency
impedance will increase and the shield will be ineffective.
(2) MELSECNET/II module
Always use a triaxial cable for the module. The radiated noise in the
band of 30 M Hz or higher can be suppressed by using a triax cable.
Earth the outer shield by the method described in (1).
(b) Always mount a ferrite core onto the triaxial cable. Mount the ferrite
core near the control cabinet outlet of each cable. Use of the TDK
ZCAT3035 ferrite core is recommended.
(b) Sandwich the exposed shield section with the and
earth to the control cabinet over a wide area.
Earth this section