Microscan MS-810, User Manual

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Ground and Shield Considerations
MS-810 Industrial Scanner User’s Manual
A-9
Appe
ndices
Appendix C — Ground and Shield Considerations
Proper grounding is necessary for
operator safety, noise reduction,
and the protection of equipment
from voltage transients. Build-
ings, 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 4). Pin 4 is
normally connected to pin 13
(chassis ground) in the scanner;
however, under certain condi-
tions (e.g., when potential differ-
ences exist between power
outlet grounds) signal and chas-
sis grounds can be isolated from
each other inside the scanner by
Microscan technicians.
Ground Loops
Ground loops , signal degradation
due to different ground poten-
tials in communicating devices,
can be eliminated or minimized
by ensuring that both the host,
scanner, and their power sup-
plies are connected to a common
earth ground.
Figure A-3 Grounding Diagram, Scanner-Host
Scanner
VIN +
+
–
RX–
RX
+ TX
–
TX
+
Chassis
Signal
Host
TX
+
TX
–
RX
+
RX
–
COM
<
C
ont
ro
lS
ig
nal
>
I/O
DC
Source
VIN +
+
–
VIN +
+
–
DC
Source
DC
Source
Scanner