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Tests
− Required transit time OPEN (Code 21):
Variable
− Required transit time CLOSED (Code 22):
Variable
During the partial stroke test, the valve
moves from its current start value to a de-
fined end value and back to the initial posi-
tion again.
The change in travel can be performed ei-
ther in steps or in a ramp function (Fig. 13).
For the test in a ramp function, additionally
the ramp times for the rising and falling
ramps need to be defined.
The PST diagnostic parameter 'Step start'
must be within the range of the current op-
Operating point + Tolerance limit
Operating point
Operating point – Tolerance limit
'Step start' – 'Step end'
∆t
falling
100
'Step start' – 'Step end'
∆t
rising
100
Fig. 13: Course of the partial stroke test with step response (left) and ramp function (right)
66
Start PST
x [%]
Start
End
Settling time before test start
Delay time after step
x
'Ramp time (falling)'
x
'Ramp time (rising)'
erating point ± 'Tolerance limit of step re-
sponse' for the partial stroke test to start.
After being activated, the test does not start
until the 'Settling time before test start' has
elapsed. Starting from the 'Step start', the
valve moves to 'Step end'. The valve remains
in this position for the time defined by the
'Delay time after step' before performing a
second step change in the opposite direction
from 'Step end' to 'Step start'. After the 'De-
lay time after step' has elapsed, the valve
moves back to its operating point.
Start PST
Delay time
Settling time before
test start
∆ t
falling
after step
∆ t
rising
EB 8389S EN
t [s]
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