Capsular Element Controller Zero And Span Adjustment - Fisher 4195 KB Series Instruction Manual

Capsular Element Controller Zero and Span
Adjustment
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 pressure to the
sensing element and a regulated supply pressure ad-
justed to the normal operating pressure (see table
1–6). Plug the controller output or connect it to a
gauge. Monitoring the controller output is not neces-
sary. However, the flapper should not contact the
nozzle at any time while performing this procedure. If it
does, adjust flapper screw 2 (the one nearest the
nozzle) to provide clearance. Refer to figure 5–19 for
the adjustment locations. Refer to figure 5–24 for the
key number locations.
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 (4195KB and KC Series only) to
0.01 minutes per repeat.
4. Adjust the rate (4195KC 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 process pressure equal to the mid-scale val-
ue of the process scale span.
7. The process pointer should be aligned with the
pointer subassembly as shown in figure 5–15. 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
Note
Note
4195KA, KB, and KC Series
that the process pointer points to the mid-scale mark
on the process scale. Tighten the screw.
9. Apply process 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 pressure equal to the process
scale upper limit.
12. The process pointer should indicate the process
scale upper limit. If not, proceed as follows:
a. If the pointer indicates less than the process
scale upper limit, rotate the pointer span adjust-
ment clockwise to increase the span. Adjust the
span adjustment screw to correct for one-half of the
error.
b. If the pointer indicates greater than the process
scale upper limit, rotate the pointer span adjust-
ment counterclockwise to decrease the span. Ad-
just the span adjustment screw to correct for one-
half of the error.
13. Repeat steps 9 through 12 until the zero and span
indications are within 1 percent of the scale limits
with no further adjustment. If proper span is achieved,
proceed to step 16. If the span adjustment screw is
adjusted to its limit and the span is still too short or too
long, proceed with step 14.
14. Within the process pointer subassembly, there are
three holes for the connection of link 1. Use procedure
(a.) or (b.) below to make the coarse span adjustment
with link 1.
a. If the span is short (process pointer indication is
less than the process scale upper limit), disconnect
link 1 from the process pointer subassembly, move
the link to the lowest hole (the hole nearest the
pointer pivot), and return to step 9. If the link is al-
ready in the lowest hole, proceed to step 15.
b. If the span is long, (process pointer indication is
greater than the process scale upper limit), discon-
nect link 1 from the process pointer subassembly,
move the link to the highest hole (the hole further-
most from the pointer pivot), and return to step 9. If
the link is already in the highest hole, proceed to
step 15.
15. At either end of link 5, there are four holes in
which the link may be connected. A coarse span ad-
justment can be made by moving both ends of link 5
up or down.
a. If the span is short (process pointer indication is
less than the process scale upper limit), disconnect
5–29