Siemens SIMATIC ET 200AL, System Manual

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Parameters/address space
4.3 Explanation of parameters
Digital I/O module F-DI 4+F-DQ 2x24VDC/2A, 4xM12 (6ES7146-5FF00-0BA0)
Equipment Manual, V1.0, 05/2021, A5E51082342-AA
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Test pulses of the dark test
Figure 4-2 Test pulses of the dark test
You configure the time between output bit pattern test sequences to either 100 or 1000
seconds. Each output bit pattern test sequence includes multiple test pulses. The interval
between two test pulses is at least 100 ms.
Maximum readback time switch on test
You can configure the maximum readback time switch on test parameter to assign the
maximum time for which the P-switch or the M-switch of a channel that is currently in OFF
state can be switched ON during a bit pattern test step. This action tests the P- and
M-switches on a channel such that only one switch is turned on at a time. Unless there is a
fault in the system (for example, actuator shorted to ground), the actuator is not energized
during either the P- or M-switch on tests. Under single fault conditions (either internal or
external to the module), test pulses applied to either the P- or the M-switch of channels in the
OFF state can repeatedly energize the actuator. You must select the parameter so that the
duration of such pulses is too short to cause the actuator to react and, therefore, cannot have
a hazardous effect on the equipment under control.
Disable dark test (max. SIL 2, Cat. 3, PL d)
You can select the check box to disable channel dark testing.
To prevent an unwanted reaction of the actuator to a dark test, you can disable the dark test
at the F-module output. An unwanted reaction can be for example, the brief de-energizing of
a magnetic drive.