3.4.3 Cable selection for power supply
Cables must be suitable for the supply voltage and approved for use in hazardous areas,
where applicable. For instance, in the U.S., explosion-proof conduits must be used in the
vicinity of the vessel.
Suitable conduits with sealing device or flame proof cable glands must be used depending
on local requirements.
Appropriate cross sectional area of wires must be used in order to prevent a too high
voltage drop to the connected device. Use 0.75 mm
2
to 2.5 mm
2
(18 AWG to 13 AWG) in
order to minimize the voltage drop.
3.4.4 Grounding
The housing should always be grounded in accordance with national and local electrical
codes. Failure to do so may impair the protection provided by the equipment. The most
effective grounding method is direct connection to earth ground with minimal
impedance. There are grounding screw connections inside the terminal compartments
which are identified by ground symbols: / . There is also a grounding screw on the
housing.
Note
Grounding the device via threaded conduit connection may not provide sufficient ground.
Grounding - Tankbus
Signal wiring of the fieldbus segment (Tankbus) can not be grounded. Grounding one of
the signal wires may shut down the entire fieldbus segment.
Shield wire ground
Tankbus
To protect the fieldbus segment (Tankbus) from noise, grounding techniques for shield
wire usually require a single grounding point for shield wire to avoid creating a ground
loop. The ground point is typically at the power supply.
The Rosemount Tank Gauging devices are designed for “daisy-chain” connection of shield
wiring in order to enable a continuous shield throughout the Tankbus network.
Primary/Secondary Bus
Cable shield for the Primary and Secondary Bus should normally be grounded at host or
System Hub end only.
Installation Reference Manual
December 2019 00809-0100-2410
32 Reference Manual
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