11
1. Slide pointer puller along pointer until pin protruding from tip of screw
in pointer puller is directly over movement shaft and arms of pointer
puller are directly under pointer.
2. Gently turn knurled head of screw clockwise, pushing pin against move-
ment shaft and lifting pointer with arms. Finger pressure should be
sufficient to pull the pointer free. If more pressure is required, insert an
Allen wrench into head of the screw for leverage. Avoid applying exces-
sive pressure, which can cause the pin to break.
3-6. Indicator Calibration
(DP=Differential Pressure) (See Warning on pg. 9)
1. Securely mount instrument in an
approximately level position and
connect DPU into the test setup, as
described in the Model 199 DPU
manual.
2. Apply 50% differential pressure and
align linkage between drive arm and
movement as shown in Figure 3-3.
Release pressure from DPU.
3. Check pointer for
zero indication.
If necessary, set
pointer to zero by
slipping pointer on
hub (hold pointer
with fingers and
turn hub with a
wrench).
4. Apply 100%
pressure. If pointer exceeds full-scale, lengthen the movement range arm
by by turning the range adjust screw counterclockwise. If the pointer does
not reach full scale, shorten the range arm by turning the range adjust screw
clockwise.
5. Release pressure. Set pointer to zero using pointer hub for zero adjustment.
6. Repeat as necessary to obtain zero and full-scale readings.
7. Apply 50% differential pressure. If pointer does not indicate 50% scale, a
linearity adjustment is necessary. Loosen drive arm screw and move arm to
shift pointer in direction of error a distance of about 10 times linearity error.
(50% DP) Tighten drive arm screw.
8. Release pressure and reset pointer at zero. Check the span. If gear in move-
ment reaches limit of travel as a result of linearity adjustment (step 7), slip
range arm along gear approximately 5 degrees from normal 37.5 degree
angle to approximately 43 degrees. Range arm is slipped by applying pres-
sure to range arm with thumb, while holding gear firmly in place. Retest
pointer response at 50%, 0%, and 100% of full-scale differential pressure,
and adjust linkage until readings are acceptable.
figure 3-3.
linkage alignment
(50% differential
pressure)
