Connecting To Power Supply; Preparing The Connection; Input Mode Active/Passive; Connection Procedure - Vega VEGAMET 381 Mise En Service

5 Connecting to power
supply
5.1

Preparing the connection

Safety instructions
Always keep in mind the following safety inst-
ructions:
Warning:
Connect only in the complete absence
of line voltage.
•
Connect only in the complete absence of
line voltage
•
If overvoltage surges are expected, overvol-
tage arresters should be installed
Note:
Install a separating facility for the
instrument which is easy to access. The
separating facility must be marked for
the instrument (IEC/EN 61010).
Safety instructions for Ex applications
In hazardous areas you must take note
of the respective regulations, conformity
and type approval certificates of the
sensors and power supply units.
Voltage supply
The power supply can be 20 ... 253 V AC,
50/60 Hz or 20 ... 253 V DC.
Connection cable
The voltage supply of VEGAMET 381 is con-
nected with standard cable according to the
national installation standards.
The instrument is connected with standard
two-wire cable without screen. If electromag-
netic interference is expected which is above
the test values of EN 61326 for industrial areas,
screened cable should be used.
Make sure that the cable used has the required
temperature resistance and fire safety for max.
occurring ambient temperature
Cable screening and grounding
Connect the cable screen on both ends to
ground potential. In the sensor, the screen must
be connected directly to the internal ground
terminal. The ground terminal outside on the
sensor housing must be connected to the
VEGAMET 381 • 4 ... 20 mA signal conditioning instrument

5 Connecting to power supply

potential equalisation.
If potential equalisation currents are expected,
the screen connection on the side of VEGAMET
381 must be made via a ceramic capacitor
(e. g. 1 nF, 1500 V). The low frequency potential
equalisation currents are thus suppressed, but
the protective effect against high frequency
interference signals remains.
Connection cable for Ex applications
Take note of the corresponding instal-
lation regulations for Ex applications. In
particular, make sure that no potential
equalisation currents flow over the cable
screen. In case of grounding on both
sides this can be achieved by the use
of a capacitor or a separate potential
equalisation.
5.2

Input mode active/passive

With the function switch you can changeover
between active and passive operation of the
measuring data input.
•
In active mode, VEGAMET 381 provides the
power for the connected sensors. Power and
measurement data are transmitted over the
same two-wire cable. This mode is provided
for connection of measuring transducers
without separate power supply (sensors in
two-wire version).
•
In passive mode the sensors are not powe-
red, only the measured value is transmitted.
This input is for connection of transmitters
with their own separate voltage supply (sen-
sors in four-wire version). The VEGAMET
381 can also be looped into the existing
circuit like a normal ammeter.
5.3

Connection procedure

Proceed as follows:
1. Mount VEGAMET 381
2. Connect sensor cable to terminal 1 and 2,
and where applicable, connect the screen
3. Connect power supply (switched off) to
terminal 5 and 6
4. If necessary, connect fail safe and operating
relay as well as current output
The electrical connection is finished.
25