Figure 4-2. Installation of mercury-(type A-1 modified).

TM 9-6685-202-14

NOTE

(a) Prepare the barometer for use as

Keep pipet tip slightly above mercury

specified in paragraph 3-5.

surface when removing mercury.

(b) Pour approximately 6-1/2 pounds of

This will help skim off impurities that

triple-distilled mercury into a clean filtering flask MS-

may have accumulated during the

306066-3.

filling operation.

Always remove

(c) Remove the cistern nipple, install

pipet completely from cistern when

antisplash tube 7913094 into bottom of cistern nipple,

checking scale zero since the

and reinstall the nipple in the cistern.

vacuum source will cause a slight

(d) Connect the barometer, filtering

pressure differential between the

flask, and glass trap to the vacuum pump as shown in

cistern and barometer tube.

figure 4-2.

(f) Reinstall the cistern nipple and

tighten it securely.

(2) Type A-1 Modified

MI (C) 6685-202-14-4-2

Figure 4-2. Installation of mercury-(type A-1 modified).

reinstall cistern nipple securely.

(e) Operate the vacuum pump until 50

microns is indicated on the vacuum gage with both

(i) Excess mercury can be removed

valves open.

from cistern in accordance with paragraph 4-5 b (1) (e)

above.

(f) When this pressure is reached, tilt

the filtering flask over slowly to let the mercury run down

c. Checking the Computing-Correcting Mechanism

the side of the tube. Add mercury to bring the level up

(Type A-1 only). The computing-correcting mechanism

to zero on the main scale.

should be checked when the barometer is originally set

up, thereafter every 6 months, or any time the

(g) Deenergize the vacuum and slowly

barometer has been subject to damage. Fastened to

raise the pressure to ambient on the cistern and

the sighting ring slide is a vernier strip which, with the

barometer tube.

applied correction

(h) Remove antisplash tube and

4-6