Samson 373 Series Operating Instructions

76 EB 8389 EN
Tests
− Characteristic selection (Code 20): Linear
− 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-
ned 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 dened.
The PST diagnostic parameter 'Step start'
must be within the range of the current op-
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 dened 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.
The 'Scan rate' denes the time interval be-
tween which the measured values are re-
corded during the test.
Settling time before test start
Delay time after step
Settling time before
test start
Delay time
after step
End
Start
Operating point
Operating point –
Tolerance limit
Operating point +
Tolerance limit
∆t
falling
∆t
rising
Start PST
Start PST
t [s]
x [%]
∆t
falling
‘Step start’ – ‘Step end’
x ‘Ramp time (falling)’
100
∆t
rising
‘Step start’ – ‘Step end’
x ‘Ramp time (rising)’
100
Fig.13: Course of the partial stroke test with step response (left) and ramp function (right)

Samson 373 Series Specifications

General

Brand	Samson
Model	373 Series
Category	Valve Positioners
Language	English