Appendices
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MS-850 Raster Scanner User’s Manual
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Appendix K — Grounding and Shielding
Proper grounding is necessary for operator safety, noise reduction, and the protec-
tion of equipment from voltage transients. Buildings, including any steelwork, all cir-
cuits, 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). 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 techni-
cians.
Noise Interference
Noise interference
can be minimized if
cabling subject to noise interference is
twisted and/or shielded or encased in
grounded conduit, and the conduit or
shielding (“drain” line) is grounded only to
earth ground at one end. The cable has its
shield attached to chassis and DC ground
internally.
Ground Loops
Ground loops
, signal degradation due to different ground potentials in communicat-
ing devices, can be eliminated or minimized by ensuring that both the host, scanner,
and their power supplies are connected to a common earth ground.
MS-850
Ho
Shielding
Cabling
Earth
