Mounting Platform Assembly.

TM 9-6685-202-14

(4) Barometer Tube Assembly.

The

(1) Mounting Platform Assembly.

The

barometer tube assembly consists of a glass barometer

mounting platform (fig. 1-2) serves as a level platform

tube (fig. 1-2) with a gasket for sealing it to the base,

for mounting the barometer proper. Two sensitive

and a tube seal valve assembly. The glass tube is the

bubble levels and three leveling screws are provided. A

container for the mercury column and is made of

battery compartment, a pushbutton switch for the light,

precision bore pyrex tubing. The lower end connects to

and the calibration curve for the instrument are also

the cistern by means of the connecting passage in the

included.

barometer base. The upper end is closed off by the

tube seal valve which is operated through a rubber

(2) Cistern and Base Assembly.

The

diaphragm. The rubber diaphragm makes it possible to

mounting platform (fig. 1-2) consists of a stainless steel

evacuate the area above the valve, which in turn makes

base on which is mounted the cistern, the barometer

it possible to develop a high vacuum above the mercury

base, and the barometer tube. The cistern is a precision

column in the tube, with an ordinary vacuum pump. An

bore pyrex cylinder. The barometer base incorporates a

evacuation stem, protruding from the side of the tube

connecting passage between the cistern and the

above the valve, connects to the tube evacuation nipple

barometer tube which can be blocked to seal all mercury

with a short piece of rubber or plastic tubing.

in the cistern during shipment of the barometer. The

cistern is pressure sealed with gaskets to the base on

(5) Scale

and

Computing-Correcting

the lower end and to a cistern lid at the upper end. The

Mechanism.

The scale and computing-correcting

lid incorporates a cistern nipple and gasket for

connecting the barometer to a pneumatic system under

mechanism (figs. 1-3 and 1-4) consists of a vernier

test, and a plugged hole to facilitate emptying the

scale, a vernier slide assembly, a cam bar, a cam

cistern.

The barometer base is fastened to the

positioning assembly, and a temperature-gravity scale

mounting platform by two hexagon socket head screws

with its two indices. The scale is fastened to the left

which thread into tapped holes in the platform assembly

hand rod of the barometer frame. It has two sets of

from the top of the base.

graduations, millimeters of mercury on the left hand or

pressure side (pressure graduations) and thousands of

feet on the right hand or altitude side (altitude

(3) Barometer Frame Assembly. The frame

graduations). Surrounding the scale and rod and sliding

assembly is composed of two 7/8 inch diameter rods

upon them is the vernier slide assembly. It carries the

mounted vertically on the barometer base (fig. 1-2) on

vernier scale, the altitude index, the applied correction

either side of the barometer tube. The upper end of

scale, the sighting ring, the light assembly, and the

each rod is fastened to a top mounting disc which also

correcting lever. A meniscus magnifier on a swivel

provides support for the upper end of the barometer

bracket is also mounted on the front surface of the

tube. The left-hand rod known as the scale rod, carries

vernier slide assembly. The cam bar is pivoted at its

the scale, vernier slide assembly, and the computing

lower end near the bottom of the scale. Its upper end is

correcting mechanism. The right-hand rod, known as

positioned by the cam positioning assembly, which tilts

the thermometer rod, carries a thermometer to indicate

the cam bar to the left or right of vertical, depending

the existing temperature.

The thermometer is

upon the settings of the temperature and gravity

graduated from 0to 40 .

indexes.

1-5