Ground And Shield Considerations; Figure 1-14 Grounding Diagram, Decoder-Host - Microscan MS-3000 User Manual

Chapter 1 Setup and Installation

Ground and Shield Considerations

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 25-pin connec-
tor). Pin 7 is normally connected to pin 1 (chassis ground) in the decoder;
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 decoder by Microscan technicians.
Any data line, as necessary, can be shielded. If shielding is used, isolate it
from the decoder and ground only to the host earth ground.
Noise Interference
Noise interference can be mini-
mized 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 the host, as shown in
figure 1-14. You might need to
examine and if necessary cut
the shielding connection at or
near the concentrator 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, concentrator, and their power supplies are connected to a common
earth ground.
1-14
MS-3000 Single Head Decoder User's Manual
HOST
Shi e l d i n g
Communications
Cable
Earth Ground
D e co d er

Figure 1-14 Grounding Diagram, Decoder-Host