The following intrinsically-safe equipment can be connected to Ex digital input modules:
No. of channels
Connectable intrinsically-safe equipment
Initiators to DIN 19 234 (NAMUR), wired contacts
The Ex digital input modules have the following mechanical features:
The rugged plastic housing contains:
Green LEDs for each circuit to indicate “1” signal (contact closed or I > 2.1 mA with NAMUR encoders to DIN 19234)
Red LED for each circuit to indicate wire break or short circuit
Slot for front connector and cable guide, protected by the front cover
Labeling area on the front cover.
The module is mounted on the DIN rail and connected to the adjacent modules via bus connectors.
There are no slot rules; the addresses of the inputs are predetermined by the slot.
The modules are wired by means of a plug-in front connector. When they are first plugged in, a coding element clicks into place so that the connector will only fit into modules of the same type. The front connector contains a special barrier for covering the module’s 24 V load current supply. When the module is replaced, the front connector can be used in its fully wired state for the new module of the same type.
Ex digital input modules convert the level of the external binary signals of the intrinsically-safe equipment from the Ex field into the internal signal level of the PLC.
SM321, 4DI, DC24V, HAZARDOUS AREAS
Load voltage L+
● Rated value (DC)
● Reverse polarity protection
from load voltage L+ (without load), max.
from backplane bus 5 V DC, max.
Type of output voltage
via the inputs
Power loss, typ.
Number of NAMUR inputs
● Rated value (DC)
8.2 V; from internal power circuit supply
● on wire-break, max.
● on short-circuit, max.
for NAMUR encoders
— for signal “0”
0.35 to 1.2 mA
— for signal “1”
2.1 to 7 mA
Input delay (for rated value of input voltage)
● Input frequency (with a time delay of 0.1 ms), max.
for NAMUR inputs
Yes; 0.1 / 0.5 / 3 / 15 / 20 ms (plus 0.25 ms preparation time)