Owner's manual

SECTION IV. CALIBRATION
4-l. CHECK POWER POSITIONER CALIBRATION.
Use the. following procedure to check calibration of
pcmw positioner. Figure 4-1, Calibration Flowchart,
is provided as a quick reference guide.
NOTE
TO perform the following calibration
procedures, reference values for percent
travel are needed. Values for linear, square
root, and square outputs are provided in
Table 4-l. Also a blank column for a
characterized cam is provided. If cam was
characterized, percent travel was recorded
upon installation to complete calibration
sequence. If percent travel was not recorded
when cam was sbaped, calibrate stroke of
power positioner (paragraph 4-2), then refer
to paragraph 2-6b.2 and perform procedure
to shape cam. Record fmdings in Table 4-1.
a. Measure distance that controlled device’s
operating arm travels out from 0% signal air to
100% signal air. Record this value as total
b. Set signal air to 0%.
c. Measure distance that controlled device’s
operating arm moves out from 0% signal air to
10% signal air. Divide measurement by total
distance from step a. Record this as percentage
output travel for 10% signal air.
d. Measure and record percentage of output have1
for 20% to 100% in 10% increments and record
as percentage output. Thii recorded data will be
compared to reference data in Table 4-1.
e. Compare recorded readings with percent output
desired in Table 4-1. Use respective columns for
characterized systems, linear, squares root, or
square cams. If recorded readings are equal to
desired values, system does not need calibration.
If recorded vahxs do not equal desired values,
continue checking procedure.
f. Set signal air to 0%.
g. Measure distance from top surface of packing
cover to bottom edge of clevis head. Label this
distance “A”.
Table 4-1. Device Travel (%).
PERCENT SIGNAL
AIR PRESSURE
0
10
20
30
40
50
60
70
80
90
100
r
LINEAR (x) SQUARE ROOT (s,,
0
0.0
10
31.6
20 44.8
30
54.8
40 63.25
50 70.7
60 77.5
70 83.7
80 89.4
90 94.9
100 100.0
PERCENTDRIVEN LEVER TRAVEL
i
SQUARE (9) CHARACTERIZED
0.0
1.0
4.0
9.0
16.0
25.0
36.0
49.0
64.0
81.0
100.0