Connecting To Power Supply; Preparing The Connection - Vega VEGATRENN 141 Operating Instructions Manual

Note safety instructions
Take note of safety
instructions for Ex
applications
Voltage supply
Select connection cable
Cable screening and
grounding
Select connection
cable for Ex applica-
tions
HART communication
VEGATRENN 141 • 4 ... 20 mA/HART
5

Connecting to power supply

5.1

Preparing the connection

Always keep in mind the following safety instructions:
•
Connect only in the complete absence of line voltage
•
If overvoltage surges are expected, overvoltage arresters should
be installed
In hazardous areas you must take note of the respective regulations,
conformity and type approval certificates of the sensors and power
supply units.
The nominal range of the voltage supply can be 24 ... 230 V AC
50/60 Hz or 24 ... 65 V DC. You can find details on the voltage supply
in the technical data.
The voltage supply of VEGATRENN 141 is connected with standard
cable according to the national installation standards.
The sensors are connected with standard two-wire cable without
screen. If electromagnetic interference is expected which is above the
test values of EN 61326 for industrial areas, screened cable should
be used. In general, cable screening is necessary in HART multidrop
mode.
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 on the outside of the sensor housing
must be connected to the potential equalisation (low impedance).
If potential equalisation currents are expected, the connection on the
processing side 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 interfer-
ence signals remains.
Take note of the corresponding installation regulations for Ex applica-
tions. 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.
The instrument is equipped with communication sockets in the front
for connection of a VEGACONNECT or another HART handheld as
well as an integrated HART resistor.
If the resistance of the connected processing system is less than
230 Ω, the digital adjustment signal is extremely damped or short-cir-
cuited. Digital communication with the PC is then no longer possible.
With low impedance processing systems, a resistor of approx. 230 Ω
must be looped into the 4 ... 20 mA cable. This resistor is already inte-
grated in VEGATRENN 141 and can be chosen through the selection
of the respective terminals.
5 Connecting to power supply
9