7. Apply 50% differential pressure to the high-pressure side. Arrange the
differential pressure linkage as shown on page 12. Set a 90° angle between the
drive arm and link. By varying the length of the link, set a 90° angle between
the range arm and link. Slip the range arm to 50% on the chart.
8. Remove pressure. The pen should indicate zero. If the pen deviates less than
10% from zero in either direction, perform fine adjustment by using the pen
zero adjust screw (refer to page 12) and proceed to step 8.b. If the pen deviates
more than 10% from zero, make adjustments as follows:
a. Rotate pen arm and shaft by gripping the range arm and forcing (or
slipping) the pen until it indicates zero. The pen arm and shaft should
rotate at the range arm pivot point without loosening the range arm lock
screw.
b. Apply 100% pressure. Make the necessary adjustment by turning the
range arm adjust screw counterclockwise if the pen is slightly underranged
and clockwise if the pen is slightly overranged. Repeat zero and 100%
adjustments until calibration at these points is achieved.
c. Apply 50% pressure. The pen should be on the 50% chart line.
If the pen is low, lengthen the linkage to make a correction 40 times as
great in the low direction. Adjust the pen to 50% as in step 8.a. (refer to
page 12).
If the pen is high, shorten the linkage to make a correction 40 times as
great in the high direction. Adjust the pen to 50% as in step 8.a. Assure all
linkage screws are retightened.
9. Repeat step 8 until calibration of all three points (0, 50, and 100% indication)
is achieved. To assure accuracy, a nine-point calibration check (1, 24, 50, 74,
and 100% ascending and descending) must be run.
14
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