Connecting To Power Supply; Preparing The Connection; Wiring Plan - WIKA LH-20 Betriebsanleitung

4 Connecting to power supply

4 Connecting to power supply

4.1 Preparing the connection

Safety instructions
Generally connect the instrument only in the
complete absence of line voltage.
The instrument is equipped with an integrated
overvoltage protection. For additional protection of
the signal circuit, we recommend further external
overvoltage arresters.
Select power supply
Power and current signal are carried on the same
2-wire conductor in the suspension cable. The
permissible voltage range can differ depending on
the instrument version.
The data for power supply are specified in chapter
"Technical data".
Keep in mind the following additional factors that
influence the operating voltage:
Output voltage of the power supply unit can be
l
lower under nominal load (with a sensor
current of 20.5 mA or 22 mA in case of fault
message)
Influence of additional instruments in the circuit
l
(see load values in chapter "Technical data")
Select installation cable
The instrument is connected with standard two-
wire installation cable without screen. If electro-
magnetic interference is expected which is above
the test values of EN 61326 for industrial areas,
screened installation cable should be used.
Cable screening and grounding
If screened installation cable is necessary, connect
the cable screen to ground potential on both ends.
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 interference signals remains.
The metallic parts of the instrument (transmitter)
are conductively connected to the screen of the
suspension cable.
WIKA Operating instructions – Submersible pressure transmitter model LH-20

4.2 Wiring plan

4 ... 20 mA
Fig. 11: Wire assignment, suspension cable
1
Blue (-): to power supply or to the processing system
2
Brown (+): to power supply or to the processing system
3
Shielding
4
Breather capillaries with filter element
4 ... 20 mA/HART
Fig. 12: Wire assignment, suspension cable
1
Brown (+): to power supply or to the processing system
2
Blue (-): to power supply or to the processing system
3
White: for processing of the integrated Pt 100 (power supply)
4
Yellow: for processing of the integrated Pt 100 (measurement)
5
Red: for processing of the integrated Pt 100 (measurement)
6
Black: for processing of the integrated Pt 100 (power supply)
7
Shielding
8
Breather capillaries with filter element
4
1
2
3 2
8
1
2
3
4
5
6
7
21