Installation of Batteries

TM 9-6685-202-14

3-4. Installation of Batteries

(a) Using a sturdy table, tilt the barometer

over backwards (cistern side down) until the tube and

Batteries are not shipped with the instrument and

scale are approximately horizontal. Support the top of the

should be procured by the using activity. Two BA-30, type

barometer to maintain this position. The cistern will be

C, dry cells, Federal stock number 6135-120-1020(which

below the tube and slightly more than half full of mercury.

fit a standard flashlight), are required.

The mercury locking screw will be visible in the bottom of

the cistern.

(b) Remove the off-center hexagonal

a. Remove the battery screw (fig. 1-2) on the right-

head shipping plug nearest the mercury tube in the cistern

hand side of the mounting platform.

lid.

b. Insert the battery screw in the tapped hole in the

shipping plug hole and unscrew the mercury locking screw

end of the battery tube. Pull out the battery tube.

in the bottom of the cistern (fig. 3-1) until it is stopped by

the small shouldered stop screw at its edge. This valve is

c. Insert the batteries into the tube with the center

left open and is closed only when sealing mercury in the

terminal of each battery pointed toward the closed end of

cistern for shipment.

the tube. Reinstall the battery tube in the mounting

platform and lock it in place with the battery screw.

CAUTION

Do not remove the small shouldered

3-5. Preparation for Use

stop screw or the mercury locking

screw.

a. Type A-1. A power-driven rotary vacuum pump

is supplied with the barometer to provide the barometer

(d) Replace the shipping plug with the

with a suitable vacuum source which will reduce the

cistern nipple (fig. 1-2), making sure there is no dirt on the

pressure to at least 100 millitorrs (0.1 mm).

cistern lid or nipple gasket.

See paragraph 3-7 for pump operation. To operate as a

NOTE

calibrating pressure measuring instrument, a controlled

Be sure to install the nipple gasket or

source of at least 20 pounds per square inch gage

the cistern will leak.

pressure is also required. The barometer achieves its best

accuracy and ease of reading when installed in a well-

lighted, well-ventilated, or air-conditioned room.

(e) Tighten the cistern nipple securely

with approximately 30 pounds pull on an eight-inch

wrench. Clamp off the end of the rubber tubing connected

NOTE

to the nipple with the clamp provided.

If possible, use clean or filtered sir

when operating the instrument to

avoid contamination of the mercury or

(f) Connect a tube from the vacuum

frequent clogging of the cistern nipple.

pump to the tube-evacuation nipple (fig. 1-2). With the

cistern nipple tube clamped off, start the vacuum pump

The instrument should be placed at a point of minimum

and open the tube seal valve by turning the tube seal knob

vibration, near a wall or supporting column allowing at

(fig. 1-2) clockwise as viewed from the top of the

least 10 square feet of floor space. A sturdy table about

barometer. This lifts the ball valve from its seat inside the

30 inches high is desirable.

glass tube. If the barometer is being set up after shipment

or storage, allow the pump to evacuate the tube and

NOTE

cistern for at least two hours before proceeding to the next

It is not necessary to fill the barometer

step. This will remove any traces of moisture which may

have gotten into the tube during shipment or storage.

with mercury on delivery from the

manufacturer since it Is already filled

and the mercury locked in the cistern

(2) Preliminary Adjustments. When all traces

by the mercury locking screw.

of moisture have been removed from the barometer tube,

required,

fill

the

barometer

perform the following preliminary adjustments to prepare

accordance with the instructions

the barometer for use:

specified in paragraph 4-5b.

(a) While the pump is running, move the

(1) Removal of Moisture. To remove traces of

barometer so that the bottom of the base is even with the

moisture which may have entered the barometer tube

edge of the table.

during shipment, proceed as follows:

3-2