Installation Guidelines
3.3 Electrical Connections
LDS 6
32
Operating Instructions, 01/2009, A5E00295894-05
3.3.3
Signal Cable Connection
CAUTION
The signal voltages must be electrically isolated extra-low voltages (SELV). The maximum
voltage potential accessible to persons is 33 V
eff
or 46,7 V peak or 70 V dc. If several SELV
voltages are available, then it is possible that the sum of these potentials is higher than that
allowed to get in contact with the human body.
WARNING
The signal cables must only be connected to devices which guarantee safe isolation from
their power supply.
If signals (i.e. analog output 4-20 mA) are to be routed into a potentially explosive
atmosphere of zone 1, they must be intrinsically safe. Supplementary retrofitting of the
analyzer with energy-limiting modules is necessary.
The Ex identification of these modules must be clearly visible on the housing:
● The signal cables in the rack mount analyzer are connected to the DSUB plugs at the
rear.
● RC elements must be connected according to the figure "Spark suppression" below as a
measure to suppress the generation of sparks across the relay contacts (i.e. limit relays).
Note that the RC element results in a drop-out delay for an inductive component (i.e.
solenoid valve). The RC element should therefore be dimensioned according to the
following rule-of-thumb:
R [Ω] ≅ 0.2 x R
L
[Ω] C [µF] ≅ I
L
[A]
Additionally, make sure that you only use a non-polarized capacitor C.
Note
When using direct current, it is possible to fit a spark suppression diode instead of the RC
element.
The cables to the relay outputs and binary inputs as well as the analog inputs and outputs
must be screened. They must be connected to the corresponding trapezoidal DSUB plug
according to the diagram "Pin assignments for I/O connectors". The conductor cross-section
should be 0.5 mm
2
. It is recommended to use cables of type JE-LiYCY... BD. The cable
length of the analog outputs depends on the load.