Endress+Hauser Tankvision Gauge Link NXA20, Руководство по эксплуатации

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Tankvision Gauge Link Installation
Hauser 13
The Tankvision Gauge Link is regarded as permanently connected equipment. An integral
fuse is provided for overcurrent protection. Protection against electric shock is by double
insulation. It is recommended that the mains supply terminals be connected to the source of
supply by means of an approved flexible cord/cable.
The supply for the Tankvision Gauge Link should be taken from a circuit breaker or switch/
fuse combination to provide electrical isolation external to the Tankvision Gauge Link and
overcurrent protection for the supply cable. This means of isolation should be clearly labelled
as to its function and should be located within easy reach of the Tankvision Gauge Link and
be easy to operate.
5.2.2 Functional earthing terminal
A functional earthing terminal is provided at the lower right of the front panel. This terminal
is used for non-safety earthing of the electronic interface circuits of the Tankvision Gauge
Link, e.g. for EMC purposes.
The functional earthing terminal is electrically separate from and not connected to the earth
terminal of the mains power supply connector.
The functional earthing terminal should be connected to the plant equipotential “ground”
using wire of 4mm
2
(12 AWG) or larger section, with a resistance less than one Ohm.
5.2.3 Status relay connections
The status relay connection at the lower left of the front panel is not used by the Tankvision
Gauge Link. No connection should be made to these terminals.
5.2.4 Host port connections
Host port connection is towards the centre of the front panel. The Modbus host port uses
EIA/TIA-485 (RS-485) “two wire” interface. This provides the “A” / “B” data signal lines and
the “C” common connection.
Note that the polarity of the “A” / “B” data signals is in accordance with the EIA/TIA-485
standard. Many third party devices with “RS-485” interfaces have the sense of the “A” / “B”
lines reversed. When connecting to such devices, it may be necessary to “cross” the “A” and
“B” connections between the devices to obtain the correct signal polarity.
The “S” terminal is provided for connection of the cable screen. This terminal is internally
connected to the functional earthing terminal of the Tankvision Gauge Link (at lower right
of front panel).
Bus termination and biasing are controlled by software selectable settings in the Tankvision
Gauge Link. By default, these are enabled for point-to-point links or the devices in a multi-
drop network that are at the outer “ends” of the cable. If the Tankvision Gauge Link is part
of a multi-drop network and is not the “end” device on the cable, the termination and biasing
may be disabled. For details of these settings,
→
ä
17.
The host RS485 connection offers transient overvoltage protection compatible with RS485
signal level.
5.2.5 Field port connections
Field port connection is towards the right of the front panel. The connections will depend
upon the interface.
For Enraf Bi-Phase Mark and “SAAB” Rosemount TRL/2, the fieldbus uses a two wire
connection. The polarity of the connection is not important.
The “S” terminal is provided for connection of the cable screen. This terminal is internally
connected to the functional earthing terminal of the Tankvision Gauge Link (at lower right
of front panel).
Both the Enraf Bi-Phase Mark and SAAB Rosemount TRL/2 fieldbuses are galvanically
isolated and offer over voltage protection commensurate with the original gauge
manufacturers’ equipment.
The Tankvision Gauge Link will be supplied as two different versions, one supporting the
Enraf Protocol and the other supporting the SAAB Rosemount TRL/2 protocol.