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5 Connecting to power supply
VEGAMET 342 • 4 … 20 mA
63731-EN-221107
5 Connecting to power supply
5.1 Preparing the connection
Always keep in mind the following safety instructions:
•
The electrical connection must only be carried out by trained,
qualified personnel authorised by the plant operator.
•
If overvoltage surges are expected, overvoltage arresters should
be installed.
Warning:
Only connect or disconnect in de-energized state.
The data for power supply are specified in chapter "
Technical data
".
The voltage supply is connected with standard cable according to the
national installation standards.
Standard two-wire cable can be used to connect the sensors.
Note:
If the temperatures are too high, the cable insulation can be dam-
aged. Hence keep apart from the ambient temperature also the self-
heating of the instrument for the temperature resistance of the cable
in the connection compartment in mind.
1)
When used in the USA/Canada, only cables with copper conductors
may be used.
5.2 Sensor input mode active/passive
Through the selection of the terminals, you can choose between ac-
tive and passive operation of the sensor input.
•
In active mode, the controller provides the power for the con-
nected sensors. Power and measurement data are transmitted
over the same two-wire cable. This mode is provided for connec-
tion of measuring transducers without separate power supply
(sensors in two-wire version).
•
In passive mode the sensors are not powered, only the measured
value is transmitted. This input is for connection of transmitters
with their own separate voltage supply (sensors in four-wire ver-
sion). The VEGAMET 342 can also be looped into the existing
circuit like a normal ammeter.
Note:
With a VEGAMET 342 in Ex version, the passive input is not available.
5.3 Connecting
The power supply and the inputs and outputs are connected via
removable screw terminals. You can find information on the max. wire
cross-section in the technical data.
Safety instructions
Voltage supply
Connection cable
Connection technology
1)
With an ambient temperature ≥ 50 °C (122 °F) the connection cable should
be suitable for an ambient temperature which is at least 20 °C (36 °F) higher.
