schmersal PROTECT-PSC - Page 79

System description
3
Instruction Manual PROTECT-PSC
V 2.6R01 / 04.19
3–47
3.9.2 Safety functions
Test pulses
The inputs are self-monitored by test pulses. Pulses of 450 to 500 µs are generat-
ed every 15 ms. The output is switched off for this brief period.
It must be insured that the downstream actuators cannot be affected by the test
pulse.
Channel monitoring
The correct switching of the output stage is monitored crosswise. This means that
processor A/B monitors the switching process of processor B/A. In the case of
semi-conductor outputs the power supply to the actuators can be interrupted in the
case of error using a shut-down relay. Output modules with relay outputs also
check the switching function of the positively driven internal relay.
Voltage monitoring
Every output module has an internal monitoring system of the connected power
supply of the actuators and reads out an error message in the case of an error.
Error messages
If errors occur during the above described measures or other internal/external
errors, these are read out by error messages. Every error message can be
generated by the processor A/B. The prefix (A/B) shows the processor from which
the message comes. The table below provides an excerpt from the possible error
messages of the input modules. A complete list of all error messages is provided in
Chapter 7.3.3.
Test
Error code
Meaning
Supply actuators
A/B 043-14
Supply voltage for the actuators too low or
non-existent
Shut-down relays
A/B 043-15
Error in the internal shut-down relay (24VDC
Test pulse
A/B 043-31
Test pulses not detected
Channel
monitoring
A/B 043-32
Discrepancy in reading back the output level
Relay contact
A/B 043-33
Error in output relay
T
T
a
a
b
b
l
l
e
e
3
3
-
-
1
1
7
7
S
S
e
e
l
l
e
e
c
c
t
t
e
e
d
d
e
e
r
r
r
r
o
o
r
r
m
m
e
e
s
s
s
s
a
a
g
g
e
e
s
s
o
o
f
f
t
t
h
h
e
e
o
o
u
u
t
t
p
p
u
u
t
t
m
m
o
o
d
d
u
u
l
l
e
e
s
s
7.3.3 / 7-5