Chapter 9
165
Logic programming – Function blocks
Feedback error, Directional error and Fault present
Generally it is expected that the Feedback 1/2 input always takes the inverted value
of the related Control input before the configured Max. switch-on feedback delay
(T
ON
) or Max. switch-off feedback delay (T
OFF
) has expired.
The Feedback error output becomes High, if …
the Control input changes from Low to High and the related Feedback input is Low
(irrespective of T
ON
and T
OFF
),
Or
T
ON
is greater than zero and the Control input changes from Low to High and the
related Feedback input does not change from High to Low before T
ON
has expired,
Or
T
OFF
is greater than zero and the Control input changes from High to Low and the
related Feedback input does not change from Low to High before T
OFF
has expired,
Or
Continuous monitoring when valve is active is active and the Control input is High
and the related Feedback input changes to High.
The Directional error output becomes High, if the Valve type parameter is =
Directional and the Control 1 and Control 2 inputs are High at the same time.
The Fault present output becomes High, if Feedback error and/or Directional error
is High.
The Feedback error, Directional error and Fault present outputs become Low, if all
activated Control inputs are Low and all activated Feedback inputs are High. If the
Reset condition is configured as Manual reset, a valid reset pulse must be applied at
the Reset input additionally.
The Min. reset pulse time defines the minimum required duration of the pulse at the
Reset input. Valid values are 100 ms and 350 ms. If the pulse duration is shorter than
the configured minimum pulse time or longer than 30 s, the pulse is ignored.
Ensure that the transitions of the signals for resetting fulfill the requirements of
the safety standards and regulations!
In case of a short-circuit to High (to 24 V DC) at a physical input, the evaluated signal
can have a pulse when the signal is reset due to the short-circuit detection. If such a
pulse can result in a dangerous state in the machine, the following points have to be
observed:
Ensure protected cable laying for the signal line (due to cross-circuiting to other
signal lines).
No short-circuit detection, i.e. do not reference to test outputs.
ATTENTION
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