Chapter 5
38
The graphical user interface
Element is connected to test outputs
By activating or deactivating the option Element is connected to test outputs you
can determine whether the respective element shall be tested or not. By connecting
an element to the test outputs …
short circuits to 24 V in the sensor wiring which could inhibit the switch-off condition
can be detected,
electronic sensors with test inputs (e.g. SICK L21) can be tested.
To activate or deactivate the connection to the test outputs either click on the
checkbox or on the 3D buttons on the right side.
One WS0-XTDI has 2 test sources only, even if it has 8 test output terminals.
Protect single channel inputs against short circuits and cross circuits!
If a stuck-at-high error occurs on a single channel input with test pulses that was
previously Low, the logic may see a pulse for this signal. The stuck-at-high first causes
the signal to become High and then after the error detection time back to Low again.
Due to the error detection a pulse may be generated. Therefore single channel signals
with test pulses need special attention:
If the stuck-at-high occurs on a single channel signal input with test pulses that was
previously High, the logic will see a delayed falling edge (High to Low transition).
If a single channel input is used and an unexpected pulse or a delayed falling edge
(High to Low) at this input may lead to a dangerous situation, the following
measures have to be taken:
– Protected cabling of the related signal (to exclude cross circuits to other signals)
– No cross circuit detection, i.e. no connection to test output.
This needs especially to be considered for the following inputs:
– Reset input on the Reset function block
– Restart input on the Restart function block
– Restart input on the Press function blocks (Eccentric Press Contact, Universal
Press Contact, N-break, Press Setup, Press Single Stroke, Press Automatic)
– Override input on a Muting function block
– Reset input on a Valve function block
– Reset to zero input and Reload input on a Counter function block
Note
ATTENTION
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