Calibration; Pre-Calibration; Span And Zero Adjustment - Fisher 4070 Instruction Manual

Type 4060 & 4070
Table 4. Cam Position Information
Actuator Travel Actuator Travel
greater than
0.75 inch (19.1 mm)
less than or equal to
0.75 inch (19.1 mm)
To secure the cam, make sure the screw is backed
out from the locking nut. Tighten the locking nut finger
tight then tighten the screw. Install and adjust the indi-
cator and reinstall the cover.

Calibration

Pre-calibration

Ensure that the cam is installed correctly for the ap-
propriate actuator travel and failure mode. Refer to the
"Cam Adjustment" procedure. Also ensure the pin on
the feedback lever arm assembly is positioned correct-
ly for the appropriate actuator travel. Refer to step 2 in
the "Positioner Mounting" procedure.
With the two locking screws facing you, as shown in
figure 10, there should be at least one coil of the feed-
back spring above the screws. However, the end of
the feedback spring should not touch the spring guide.
To adjust the spring, loosen the two locking screws.
Hold the two locking screws in place while rotating the
feedback spring. Tighten the locking screws.
Zero and Span Adjustment
Refer to figure 10.
1. Remove the positioner front cover.
2. Apply supply pressure to the positioner.
3. Set the input signal to the 0% value and wait for the
unit to reach steady state.
4. Rotate the zero adjustment until the actuator stem
is at its starting position. Zero is adjusted by turning
the silver thumb wheel located on the lower arm or
externally with a screwdriver through the zero adjust-
ment opening.
5. Slowly increase the input signal until the input
reaches the 100% value. Observe the actuator travel
and valve position as the input increases. Note the
actuator travel at 100% input signal.
6. Set the input signal to the 0% value.
8
Cam Orientation for Actuator
Cam
Failure Mode
Lobe Lobe
Fail Open Fail Close
60 D
30 D
SPRING GUIDE
R
R
SPAN
ADJUSTMENT
ZERO
ADJUSTMENT
A7229 / IL
Figure 10. Positioner Span and Zero Adjustment Locations
7. If necessary, loosen the locking screw and adjust
the span as follows (span is adjusted with the brass
colored thumb wheel located on the feedback spring):
If the actuator travel recorded in step 5 is short of
the desired travel at 100% input signal, rotate the span
adjustment to the left to increase span. Tighten the
locking screw.
If the travel recorded in step 5 reaches the de-
sired travel before the input signal reaches the 100%
value, rotate the span adjustment to the right to de-
crease span. Tighten the locking screw.
After the span adjustment, recheck to be sure the end
of the feedback spring is not touching the spring guide.
8. After a span adjustment, recheck the zero and ad-
just if necessary.
9. Repeat steps 4 through 8 as necessary to achieve
correct actuator travel.
LOCKING SCREW
LOWER ARM
ZERO ADJUSTMENT
COVER