Manual

5 Connecting to power supply
5.1 Preparing the connection
Always keep in mind the following safety instructions:
l Connect only in the complete absence of line voltage
l If voltage surges are expected, install overvoltage arresters
Power supply and current signal are carried on the same two-wire
cable. The voltage supply range can differ depending on the
instrument version.
The data for power supply are specified in chapter "Technical data".
Provide a reliable separation between the supply circuit and the mains
circuits according to DIN VDE 0106 part 101.
Keep in mind the following additional factors that influence the
operating voltage:
l Output voltage of the power supply unit can be lower under
nominal load (with a sensor current of 20.5 mA or 22 mA in case of
fault message)
l Influence of additional instruments in the circuit (see load values in
chapter "Technical data")
The instrument is connected with standard two-wire cable without
screen. If electromagnetic interference is expected which is above the
test values of EN 61326-1 for industrial areas, screened cable should
be used.
For instruments with housing and cable gland, use cable with round
cross-section. A cable outer diameter of 5 … 9 mm (0.2 … 0.35 in)
ensures the seal effect of the cable gland. If you are using cable with a
different diameter, exchange the seal or use a suitable cable gland.
We generally recommend the use of screened cable for HART
multidrop mode.
With plastic housing, the NPT cable gland or t he Conduit steel tube
must be screwed without grease into the threaded insert.
Max. torque for all housings see chapter "Technical data"
If screened cable is necessary, 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 housing must be connected to the potential equalisation
(low impedance).
Saf
ety instructions
Volta
ge supply
Conne
ction cable
Cable
gland ½ NPT
Cable
screening and
grounding
LEVEL TRANSMITTER 8136 • 4 … 20 mA/HART - two-wire 25
5 Connecting to power supply
41783-EN-120316