Operating Manual
9
Test pulse outputs
The two test pulse outputs T
0
and T
1
are fed from the supply voltage and
are suitable for testing the wiring of input devices.
Only inputs which operate in accordance with the zero signal principle (on
switching off) are permitted for safety-related applications.
Test pulses are allocated to inputs via the configurator in the system
software.
Each test pulse has a maximum load capacity of 0.5 A.
If the plant is sensitive to the fast on/off switching of the output test,
individual outputs may be excluded from the test through the configuration.
NOTICE
In the case of outputs that are excluded from the output test, the PSS
checks that their switch status is correct but does not check their actual
ability to switch. This means that, under some circumstances, errors will
only be detected the next time the output switches on or off. In accordance
with EN 954-1, category 2 or higher can be achieved with such an output.
An output test can be performed in the user program in order to reduce
fault detection time. If the output is switched on, proceed as follows: at a
non-critical point in the program, switch the output off and
then on again for one PSS-cycle. Follow the process in reverse if the
output is switched off. If the output does not switch correctly, the error will
be detected and registered by the PSS SB DI8O8 operating system.
NOTICE
During commissioning, an error must be simulated for every safety-related
positive-switching output, in order to detect whether an output has been
incorrectly excluded from the output test, or to check whether the output
test programmed by the user is effective. Wait until the user program sets
the output to “1” (output’s LED will light) and then generate a short circuit
between the output and 24 V. The required error reaction should then
occur.
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