Figure 3-2. Gravity correction chart.

TM 9-6685-202-14

Figure 3-2. Gravity correction chart.

following preliminary

adjustments

prepare

the

barometer for use:

(a) Remove the off-center hexagonal-

head shipping plug and replace with cistern nipple (fig.

(a) Level the mounting platform by

means of the three leveling screws, using the indication

NOTE

of the two levels in the mount platform. Clockwise

rotation of the leveling screws raises the platform.

Be sure to install the nipple gasket.

NOTE

(b) Tighten the cistern nipple securely

with approximately 30 pounds on an eight-inch wrench.

The instrument must be maintained

level within 30 seconds of arc to

reduce alignment errors to below

vacuum gage sensor as shown in figure 1-1.

0.02 mm of mercury. This is done by

(d) Connect a tube from the cistern

centering the bubbles within one

nipple to the vacuum line connection nearest the cistern.

division on the level scales.

Close valve to cistern.

(b) Deenergize vacuum pump and

(e) Connect a tube from the vacuum

carefully open both the tube and cistern to atmospheric

pump to the barometer evacuation connection.

pressure.

(f) Operate vacuum pump until 50

(c) Install mercury under vacuum as

microns is indicated on the vacuum gage. This will

remove any traces of moisture which may have gotten

(d) Loosen the set screw at the base of

into the tube and cistern during shipment and storage.

the micrometer barrel and rotate barrel until index line is

at a convenient position

(2) Preliminary Adjustments.

When the

vacuum gage indicates 50 microns, perform the

3-5