• Do not place digital or analog I/O lines in the same conduit as AC power circuits.
• Use only shielded cable for digital I/O line connections.
— Ground the shield at only one end.
— Shield-drain wires must not be more than two American Wire Gauge (AWG) sizes
smaller than the conductors for the cable.
• When inductive loads (relay coils) are driven by digital output lines, the inductive
transients must be diode-clamped directly at the coil.
• Any auxiliary equipment wired to the GC must have its signal common isolated from
earth/chassis ground.
CAUTION
SIGNAL INTERFERENCE
If you don't follow this precaution, the data and control signals to and from the GC could
be adversely affected.
Do not place any loop of extra cable left for service purposes inside the GC purged housing
near the conduit entry for AC power.
2.3.3 Grounding precautions
Follow these general precautions for grounding electrical and signal lines:
• For shielded signal conducting cables, shield-drain wires must not be more than two
American Wire Gauge (AWG) sizes smaller than the conductors for the cable. Shielding
is grounded at only one end.
• Metal conduit used for process signal wiring must be grounded at conduit support
points (intermittent grounding of conduit helps prevent induction of magnetic loops
between the conduit and cable shielding).
• A single-point ground must be connected to a copper-clad, 10-ft. long, ¾-in. diameter
(3 m long, 19.1 mm diameter) steel rod, which is buried, full-length, vertically into the
soil as close to the equipment as is practical.
Note
The grounding rod is not furnished.
• Resistance between the copper-clad steel ground rod and the earth ground must not
exceed 25 Ohms.
• On ATEX-certified units, the external ground lug must be connected to the customer’s
protective ground system via 9 AWG (6 mm
2
) ground wire. After the connection is
made, apply a non-acidic grease to the surface of the external ground lug to prevent
corrosion.
• The equipment-grounding conductors used between the gas chromatograph (GC) and
the copper-clad steel ground rod must be sized according to your local regulations.
Quick Start Guide Installation and start-up
00825-0100-3770 July 2020
Rosemount 700XA 19
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