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13
Model 581A Differential Pressure Switch
Section 3
See
Figure 3.2, page 13.
c. Replace the bezel/lens assembly.
HUB
Pointer "slipped"
rotated on hub
Hub held in place
with 1/4" wrench
Figure 3.2—"Slipping" pointer
3. To test for reverse travel, connect the pressure source to the low-pressure
(LP) housing and vent the HP housing. Apply pressure to approximately
150% of the DP range. The pointer should move approximately 5% to
10% below zero.
4. To test for overtravel, connect the pressure source to the HP housing and
vent the LP housing. Apply pressure to approximately 150% of DP range.
The pointer should move approximately 5% to 10% above the full scale
mark.
5. Apply 0, 50, and 100% of full scale pressure. If the indication is within
Scale Plate
Installation and Removal, page 14
).
6. Make sure the instrument zero indication is correct; otherwise, repeat
step 2.
7. Verify the switch set points (refer to
Changing Switch Set Point, page 20
).
Pointer Installation and Removal
During adjustment and calibration of the unit, it may be necessary to remove
and reinstall the pointer. See the following procedures for instructions.
Pointer Installation
1. Position the pointer on the movement shaft with the pointer set at zero
scale. Obtain 75% to 90% pointer hub engagement on the movement
pinion shaft. The pinion shaft must not extend through the pointer hub.It
may be necessary to enlarge the hub hole using a tapered broach (includ-
ed in the calibration toolkit, Part No. 9A-0288-1032B).