WIKA LH-20 - Manual (Page 19)

19 WIKA Operating instructions - Submersible pressure transmitter model LH-20
4 … 20 mA/HART signal cable.
With sensors without HART protocol, the ad-
justment units are suitable for measured value
indication.
You can find further information in the respective
operating instructions of the adjustment units
DIH50, DIH52 and DIH62.
3 Mounting
3.1 General instructions
Suitability for the process conditions
Make sure that all parts of the instrument in
physical contact with the process are suitable
for the exisitng process conditions. These inclu-
de in particular the process pressure, process
temperature as well as the chemical properties
of the medium.
You can find the specifications in chapter "Tech-
nical data" and on the nameplate.
Pressure compensation
The suspension cable has a capillary for atmos-
pheric pressure compensation. Thus, make sure
the cable ends in a dry environment or suitable
terminal housing.
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 depen-
ding on the instrument version.
The data for power supply are specified in chap-
ter "Technical data".
Provide a reliable separation between the
supply circuit and the mains circuits according
to DIN EN 61140 VDE 0140-1.
Keep in mind the following additional factors
that influence the operating voltage:
•
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)
•
Influence of additional instruments in the
circuit (see load values in chapter "Technical
data")
Select installation cable
The instrument is connected with standard
two-wire installation cable without screen. If
electromagnetic interference is expected which
is above the test values of EN 61326 for indus-
trial 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.
The metallic parts of the instrument (transmitter)
are conductively connected to the screen of the
suspension cable.
4.2 Wiring plan
4 … 20 mA
4
1
2
2
3
Abb. 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
1
8
2
3
4
5
6
7
Abb. 12: Wire assignment, suspension cable
1 Brown (+): to power supply or to the processing