TB 9-6660-270-50
8. Vacuum and Pressure
a. Performance Check
(1) Adjust pressure regulator (B4) on nitrogen cylinder for 16 psi and start vacuum
pump (B5).
(2) Adjust vacuum regulator (B6) as necessary to exercise TI 3 times from lowest to
highest reading. Check for smooth operation of indicator.
(3) Determine correct ambient barometric pressure from barometer (A1).
(4) Adjust vacuum regulator for ambient pressure indication on TI and disconnect
TI from vacuum regulator.
(5) If TI does not indicate ambient pressure as determined in (3) above, adjust TI
mechanical ambient adjustment screw, if applicable.
(6) Connect TI to vacuum regulator and adjust vacuum regulator for TI indications
listed in table 4 or 5.
NOTE
Change barometer to manometer function for indications above
atmospheric pressure.
(7) If barometer does not indicate within limits specified, perform b below.
(8) For applicable TI's, plot scale error on calibration correction chart and place
chart in case cover (see sample, figure 2).
b. Adjustments
(1) Repeat a(6) above, recording barometer (A1) indication for 6 to 10 TI calibration
points evenly spaced throughout the range of the TI.
(2) Make a graph plotting the TI calibration points on the abscissa (x-axis) and the
deviation (difference in barometer and TI indications) on the ordinate (y-axis) (fig. 3).
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