54
Saab TankRadar L/2
US Version. Seventh edition, June 1995
Installation Manual
12.2 Cabling for TRL/2 Bus
The TRL/2 bus requires a twisted and shielded pair with an area
of min 0.50 mm
2
(AWG 20 or similar). The maximum length of the
TRL/2 bus is 4 km. The TRL/2 Field Bus can normally use exist-
ing cables in the tank area.
Note:
Wherever two TRL/2 Buses run alongside each other, sharing the
same cable or conduit tube, individual shielding is mandatory in order to
avoid crosstalk.
12.3 Grounding
According to national code of practice the Transmitter Head or
Data Acquisition Unit can be grounded by connecting an exterior
4 mm
2
wire to a potential equalization network, or, if no such
exists, to the tank structure. A grounding lug is available on the
enclosure for this purpose.
Note:
When the enclosure is connected to a potential equalizing network
or to the tank structure, the protective ground with the power supply
must not be connected.
If the enclosure is not externally grounded, the protective ground with
the power supply should be connected.
12.4 Electrical Installation of the Radar Tank Gauge, RTG
12.4.1 The Non-Intrinsically Safe Connection (W11)
The power connection is made with two wires. The TRL/2 Field
Bus connection is made with a single pair of shielded twisted
wires.
A Junction Box is required for the non-intrinsically safe connection
of the power supply and the TRL/2 Field Bus. The junction box
can either be customer supplied or supplied by Saab Tank Control
as an option, see chapter 7. The three wires in the cable output that
are not used must be properly insulated and terminated in the
junction box.
12.4.2 The Intrinsically Safe Connection (W12)
See chapter 3.1.2 for information on number of cables in lead seal.
If the distance between the Transmitter Head and the Slave Data
Acquisition Unit is longer than 2.0 m, a junction box must be used
to connect an extension cable. This extension cable must not be
longer than 50 m. For safety reasons the ends of the unused wires
must be properly insulated and terminated. The junction box can
either be customer supplied or supplied by Saab Tank Control as
an option, see chapter 7.
A flexible protective hose for the wires is delivered with the Bar-
rier Unit or the Current Loop Card, or with the Transmitter Head
if the units have been factory installed. For reasons of electromag-
