4194A, B, and C Series
5–23
the capsules. Tighten the screw to set the length of
the pivot adjustment arm in that position.
Note
See figure 5-18. The adjustment arm of
the long pivot clevis assembly is con-
nected to a shaft that turns on bushings
at each end of the shaft. In the next
step, position the shaft so that both
bushings ‘‘float’’ inside the bearings
and do not rest against the end of either
bearing.
c. Before retightening the drive flexure screws,
hold the long pivot clevis assembly shaft in the
middle of the bushing end play. Be sure neither
bushing is resting against the inside end of either
bearing.
d. Tighten the drive flexure screws to hold the pivot
clevis assembly shaft in position.
2. Set the linearity adjustment screw on the short piv-
ot clevis assembly so the two arms of the short pivot
clevis assembly are parallel. The linearity adjustment
screw should be near the center of its slot.
3. Make certain that the process pointer and pointer
subassembly are aligned as shown in figure 5-14. If
not, loosen the zero adjustment locking screw and ad-
just the process pointer zero adjustment screw to align
the process pointer and pointer subassembly. Tighten
the zero adjustment locking screw.
4. Adjust the process differential pressure input to 50
percent of capsular element range.
5. Loosen the screw on link 5 (key 88) and adjust the
link length so that the pivot arms of the short pivot cle-
vis assembly (key 89) and the long pivot clevis assem-
bly (key 78) are parallel. Tighten the screw.
6. Complete the maintenance calibration by perform-
ing the zero and span adjustments in the following pro-
cedure.
Zero and Span Adjustment
Note
For routine zero and span calibration,
refer to the appropriate procedures in
section 3 or 4. Use the following mainte-
nance zero and span adjustment proce-
dure only if difficulty is encountered
with the routine procedure or if nonlin-
earity occurs.
Provide a means of applying process differential pres-
sure to the sensing element and a regulated supply
pressure adjusted to the normal operating pressure
(see table 1-4). Plug the controller output or connect it
to a gauge. Monitoring the controller output is not nec-
essary. However. the flapper should not contact the
nozzle at any time while performing this procedure. If it
does, adjust flapper screw 2 (the screw nearest the
nozzle) to provide clearance. Refer to figure 5-19 for
the adjustment locations. Refer to figure 5-21 for the
key number locations.
Note
Any adjustment of the process pointer
span adjustment screw requires read-
justment of the process pointer zero ad-
justment screw.
1. Remove the two machine screws (key 6) and lift off
the proportional band indicator cover (key 36).
2. Set the proportional band between DIRECT and
REVERSE.
3. Adjust the reset valve (4194B and C Series only) to
0.01 minutes per repeat.
4. Adjust the rate (4194C Series only) to OFF.
5. For a controller with manual set point, move the set
point indicator to the mid-scale mark on the process
scale. For a controller with remote set point, adjust the
remote set point pressure until the set point indicator
is at the mid-scale mark on the process scale.
6. Apply a process differential pressure equal to the
mid-scale value of the process scale span.
7. The process pointer should be aligned with the
pointer subassembly as shown in figure 5-14. If not,
loosen the zero adjustment locking screw and adjust
the zero adjustment screw to align the process pointer
with the pointer subassembly. Tighten the zero adjust-
ment locking screw.
8. The process pointer should indicate mid-scale
±
3
percent of the process scale span. If not, loosen the
screw on either link 1 or link 5 and adjust the length so
that the process pointer points to the mid-scale mark
on the process scale. Tighten the screw.
9. Apply process differential pressure equal to the
process scale lower limit.
10. The process pointer should indicate the process
scale lower limit. If not, loosen the zero adjustment
locking screw and adjust the zero adjustment screw
until the process pointer indicates the lower limit.
Tighten the zero adjustment locking screw.
11. Apply process differential pressure equal to the
process scale upper limit.
12. The pointer should indicate the process scale up-
per limit. If not, proceed as follows:
a. If the pointer indicates less than the process
scale upper limit, rotate the pointer span adjust-
