Activated Light Test - Siemens SIMATIC S7-1500 Manual

Parameters/address space
4.2 Explanation of parameters
Setting readback time switch on test with unknown actuator capacity
If the capacitance of the actuator is not known, you may have to determine the required
value for the readback time switch-on test by trial and error. This may also be necessary due
to the part variances in the actuator or external influences.
Proceed as follows:
● Set the readback time switch on test in such a way that the output channel can be read
back correctly but your actuator does not respond yet.
● For verification use the process value "0" with a minimum duration that corresponds to
the "maximum test time" parameter. If you have not configured a light test, continue by
changing the process value to "1" after the verification.
● If the output channel is passivated sporadically, set a higher value for the maximum
readback time switch on test.
● If the output channel is passivated, the readback time is too small for a connected
capacitive load. The charge of the capacitive load cannot take place during the
configured readback time. Increase the readback time.
If you have set the readback time to the maximum value of 5 ms and there is still a
passivation of the output channel, there is either an external fault or the connected capacity
is outside the permitted range.
To increase availability, we recommend that you maintain an interval to the determined limit
for the times.
4.2.3.7

Activated light test

Function
Overload and wire break are detected with a 0 signal at the output.
For a light test, a test signal is switched to the output channel while the output channel is
inactive (output signal "0"). The output channel is switched on briefly during the light test
(= "light period") and read back. A sufficiently slow actuator does not respond to this and
remains switched off.
PM operation
In contrast to the switch on test, the P-switch and the M-switch switch at the same time
during the light test and power flows through the connected load.
①
Image 4-6
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Readback
Functional principle of the light test (PM switching)
Digital output module F-DQ 8x24VDC/2A PPM (6ES7526-2BF00-0AB0)
Manual, 01/2016, A5E03858037-AA