Section 5 - Wiring Techniques Page 5-3 S1400T-2808B
5.2.3 Grounding of Cable Shields
DO NOT connect the cable shield to more than one ground point; it should only be grounded
at one end. Cable shields that are grounded at more than one point or at both ends may
have a tendency to induce circulating currents or sneak circuits that raise havoc with I/O
signals. This will occur when the ground systems associated with multipoint connections to
a cable shield have a high resistance or impedance between them and a ground induced
voltage is developed (for what ever reason, i.e., man made error or nature produced
phenomena).
5.2.4 Use of Known Good Earth Grounds
Series 2808 Transmitters should only have one connection to earth ground. This connection
is provided via the Ground Terminal that is situated on the inside of the units Electrical
Housing. Since Series 2808 Transmitters are DC-based systems, grounding does not take
into account AC power grounding considerations. These units should be connected to earth
ground when they are installed in areas that have frequent lightning strikes or are located
near or used in conjunction with equipment that is likely to be struck by lightning or if
struck by lightning may cause equipment or associated system failure. Earth Grounds must
be tested and must be known to be good before connecting the 2808 Transmitter. Earth
grounds must be periodically tested and maintained (see Section 4).
5.2.5 Earth Ground Wires
Earth connections must utilize smoothly dressed large wire. Use AWG 4 solid copper wire
with as short a length as possible. Exercise care when trimming the insulation from the
wire ends. Twists the strands tightly, trim off any frizzes and tin the ends with solder. The
earth ground wire should be clamped or brazed to the Ground Bed Conductor (that is
typically a standard AWG 0000 copper cable. The earth ground wire should be run such
that any routing bend in the cable is a minimum 8-inch radius above ground or a minimum
12-inch radius below ground. The only wired earth ground connection permitted to the 2808
Transmitter must be made via the unit’s Ground Terminal. Make sure that the connection
at the 2808’s Ground Terminal is secure.
5.2.6 Working Neatly & Professionally
Take pride in your work and observe all site and maintenance safety precautions. After
properly trimming the stranded pair wire ends, twist them in the same direction as their
manufacturer did and then tin them with solder. Install the tinned wire end into it’s
connector and then secure the associated connector’s clamping screw. Remember to check
these connections for tightness from time to time. If solid copper wire is used (in
conjunction with the DC Power System or for Earth Ground) make sure that the conductor
is not nicked when trimming off the insulation. Nicked conductors are potential disasters
waiting to happen. Neatly trim shields and whenever possible, coat them to protect them
and prevent shorts and water entry.
Remember loose connections, bad connections, intermittent connections, corroded connec-
tions, etc., are hard to find, waste time, create system problems and confusion in addition to
being costly.
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