Instruction Manual
D200158X012
4194S Controllers
July 2018
43
2. Full span stop—Adjust process differential pressure to 5 percent greater than full span pressure.
Loosen the screws (key 139) mounting the travel stop (key 83) to the mounting plate. Slide the travel stop until it is
just touching the end of the capsule stack. Tighten the travel stop mounting screws to lock it into that position.
3. Zero stop—Adjust pressure input to 0 percent of the full span.
Slide the travel stop nut (key 86), along the diaphragm capsule extension (key 82) until it is approximately 0.4 mm
(1/64‐inch) away from the travel stop. Tighten the set screw to lock the travel stop nut in that position.
Aligning the Linkage
1. Adjust the process differential pressure to 75 percent of the input span. The drive flexure (key 79) should be straight
and horizontal. If it is not, proceed as follows:
a. Loosen the screw on the adjustment arm on the long pivot assembly (key 78) and the two screws mounting the
drive flexure.
b. Adjust the length of the adjustment arm so that the drive flexure is parallel to the centerline of the capsules.
c. Tighten the screw to set the length of the adjustment arm in that position. Before retightening the screws, set
the pivot in the middle of the bushing end play.
d. Tighten the drive flexure to hold the pivot in that position.
2. Tighten the guide flexure to the mounting plate.
3. Set the linearity adjustment screw on the short pivot assembly in the middle of its slot.
4. Make certain that the process pointer and pointer subassembly are aligned (see figure 4-13). Change the length of
link 1 (key 90) to the middle of its adjustment.
5. The short (bottom) arm on the short pivot assembly (key 89) should be parallel with the process pointer and the
pointer subassembly.
6. Turn the span adjustment screw on the bottom of the process pointer counterclockwise as far as it will go so the
span adjustment bracket will be in its highest position.
7. Adjust the process differential pressure to 50 percent of full input span. Adjust the length of link 5 (key 88) so that
the pivot level arms are as close to parallel as possible.
8. To complete maintenance calibration, the zero and span adjustments must be set. Refer to the following section for
that procedure. If linearity adjustments must also be made, refer to that portion of the procedures.
9. Replace the tie bar (key 97) after the controller is calibrated.
10. Refer to the Flapper Alignment procedures.
Process Zero‐and‐Span Adjustment
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. Apply 0 percent of the process differential pressure input span.
4. Loosen the screw on link 5 (key 88) and adjust the length so that the process pointer points to scale zero. Tighten
the screw.
5. Make fine zero adjustments by loosening the zero adjustment locking screw on the process pointer and turning the
zero adjustment screw. Tighten the locking screw.
6. Apply 100 percent of the process pressure input span.
7. To increase the span, proceed as follows: