Owner's manual

13.
14.
(c) Repeat steps 11 and 12 as necessary to
make distance equal to 5 inches.
Observe piston travel while increasing input
signal to 100% and then slowly decreasing
input signal to 0%
If piston reaches top of travel before input
signal reaches 0%. use the following
procedure to calibrate piston travel.
(4
@)
Cc)
Loosen lock screw (6) and adjustment
screw (7). Pull cam (8) slightly
outward (about 1/64th inch).
Retighten adjustment screw (7) and
lock screv/ (6).
Repeat steps 13 and 14 as necessary to
make piston reach top of travel at same
time as input signal reaches 0%.
b. Reverse Acting Power Positioner. For
procedures to calibrate a reverse acting power
positioner, refer to paragraph 3-2b.
4-3. CURRENT TO PNEUMATIC SIGNAL
CONVERTER 0/P) CALIBRATION. Calibrate
cm-rent to signal converter after mounting, changing
mounted position, or when loss of control is noticed
(refer to Troubleshooting, Section V). Use the
following procedures to calibrate the signal converter
W).
a. Remove plastic caps tiom “Zero” and “Span”
adjustment holes (Figure 4-3).
NOTE
Make sure input rating of power positioner
is same as pressure rating of current to
pneumatic signal converter.
b. Set input signal value to 4 mA (20 mA if I/F’ is
in an inverse setup) and adjust “Zero” screw until
output pressure is at 0 psig. Turn screw counter-
clockwise to increase pressure, clockwise to
decrease pressure. If output pressure does not
change when screw is tamed, tarn screw counter-
clockwise until pressure starts to rise.
c. Set signal value to 20 mA (4 mA if I/l’ is in an
inverse setup).
d. Adjust “Span” screw until output pressure is at
60 psig.
e. Repeat steps b and c until no forther adjustment
is needed.
f. Replace protective caps.
PFE~~E
Figure 4-3. I/P Calibration
4-4. LINKAGE CALIBRATION.
a. m. Check angle of power positioner’s drive
lever from centerline. Compare this to angle of
device’s driven lever from centerline. If angular
measurements are not equal, use the following
procedure to adjust offset of power positioner’s
drive lever to equal offset of device’s driven
lever. When adjustment is complete, both
operating lever and driven levers must be parallel
with each other.
1. Measure angle PI from vertical centerline, to
power positioner’s drive lever centerline
(Figure 4-4). This is power positioner’s
offset.
2. Measure angle a from vertical centerline of
device being contxolled to driven lever
centerline. This is driven lever’s offset.
3. Compare angles PI and !&. Adjust length of
linkage for minor adjustments by threading
pipe in or out of clevis. Change operating
lever offset (p,) for major adjustments.