II - DCE FEL ČVUT v Praze

SIMATIC S7 Ex Digital Modules
Block diagram
S7-300
Backplane
bus
2-4
Logic
stage
Logic
stage
Fig. 2-2 shows the block diagram of the digital input module SM 321;
DI 4 x NAMUR.
Monitoring L+
module
Monitoring
internal supply
voltage
Channel 0
Channel 1
Channel 2
Channel 3
Group fault
indication (SF)
red
Status
Fault
5 V
Status
indication (0...3)
green
Fig. 2-2 Block diagram of digital input module SM 321; DI 4 x NAMUR
Evaluation
stage
8.2 V
1k
8.2 V
1k
8.2 V
1k
8.2 V
1k
L+
Load voltage 24 V
M
Sensor supply
NAMUR sensor
monitoring for
– conductor wire break
– conductor short-circuit
Contact with
monitoring for
– conductor wire break
– conductor short-circuit
(resistors connected
directly at contact
1k
10k
Contact with
monitoring for
– conductor wire break
(resistor connected
directly at contact
10k
Channel fault
indication (F0...F3)
red
Contact without
monitoring
Connection variants
I/O Modules with Intrinsically-Safe Signals
C79000-G7076-C152-04