Cashco 9540L P/P - Manual (Page 8)

IOM-9540L 8
3. A change in GAIN is normally indicated when
instability sluggishness shows up at steady
state operating conditions. If the positioner
output “LOAD” seems to rapidly oscillate (psst-
psst-psst-...,) too much gain is present and
GAIN setting should be reduced until stability
is reached. If the positioner output “LOAD”
does not react to small changes in the “SIG”,
insufficient GAIN may be present; increase
GAIN until instability (psst-psst-psst-...) is
present, then reduce as described previously.
This procedure allows the gain of the control
loop to match the dynamic requirements of
the control system.
4. Determine whether GAIN should increase or
decrease based on above text. To increase
GAIN, rotate throttle screw (42) CW; to de-
crease GAIN, rotate throttle screw (42) CCW.
To prevent overadjustment the throttle screw
(42) is located within the limiting screw (43).
This allows the throttle screw (42) to only be
adjustable a total of approximately one revo-
lution from maximum to minimum. Thus, GAIN
should be adjusted slowly in very small incre-
ments.
5. If GAIN is adjusted, ZERO resetting may be
required. Check and use Procedure V.A.
C. Setting DAMPING: (See Figure 10)
1. Increasing DAMPING introduces extra time
constant to the output “LOAD” of the positioner.
DAMPING should be increased/decreased
depending on the time observed for the posi-
tioner to respond to a large change in input
“SIG” during a non-steady state operating
condition.
2. DAMPING is factory set, and normally
requires minimal/no adjustment. However, if
determined as required, DAMPING is adjust-
able from a minimum - to - maximum ratio of
1:2.5. In its normal factory set position, the
damping screw (44) is set approximately flush
with the amplifier housing (53); this position is
minimum DAMPING. As the damping screw
(44) is screwed CW inwards, DAMPING in-
creases. DAMPING may be increased by up
to approximately three full revolutions of the
damping screw (44), which will represent maxi-
mum DAMPING.
VI. MAINTENANCE
A. Adjustment of the Positioner: (See Figure 11)
1. Component adjustment is only required when
the positioner has been disassembled or
sub-assemblies have been exchanged. All
settings performed in order to match the
positioner to the actuator are described in
Sections IV. and V.
2. See Section IV.A. for a list of required tools.
SECTION VI
Figure 11
Figure 10