Appendix D - Ground And Shield Considerations; Figure A-10 Grounding Diagram, Scanner-Host; Ground Loops - Microscan MS-7100 User Manual

Appendix D — Ground and Shield
Proper grounding is necessary for operator safety, noise reduction, and the
protection of equipment from voltage transients. Buildings—including any
steelwork, all circuits, and all junction boxes—must be grounded directly to an
earth ground in compliance with local and national electrical codes.
RS-232 signals have a common signal ground (pin 7 of the 28-pin connec-
tor). Pin 7 is normally connected to pin 1 (chassis ground) in the scanner;
however, under certain conditions (e.g., when potential differences exist
between power outlet grounds) signal and chassis grounds can be isolated
from each other inside the scanner by Microscan technicians.
Any data line, as necessary, can be shielded. If used, shielding should be
isolated from the scanner and grounded only to the host earth ground.
Noise Interference
Noise interference can
be minimized if cabling
subject to noise inter-
ference is twisted and/
or shielded or encased
in grounded conduit,
and the conduit or
shielding ("drain" line)
is grounded only to
earth ground at the
host, as shown in figure
A-10. You might need
to examine and if nec-
essary cut the shielding connection at or near the scanner cable connector.

Ground Loops

Ground loops, signal degradation due to different ground potentials in com-
municating devices, can be eliminated or minimized by ensuring that the
host, scanner, and their power supplies are connected to a common earth
ground.
MS-7100/7180 Industrial Scanner User's Manual
Ground and Shield Considerations
Considerations
Host
Scanner

Figure A-10 Grounding Diagram, Scanner-Host

Shielding
Com m unic ations
cable
Earth ground
A-9