TM 55-6610-247-40
cold bath for five minutes. Tap frame lightly and record
in same direction. A turn of the diaphragm support nut
the reading. Any reading other than 0 is an error.
results in a correction of 10 feet.
NOTE
Table 2-2. Progression of Error
Agitate liquid before taking reading.
ALTITUDE
ALLOWABLE CHANGE
When tapping mechanism, strokes
IN FEET
OF READING IN FEET
should be made vertically. Horizontal
0
+30
tapping may move mechanism sideways
6,000
+50
and so shift sector position.
12,000
+80
CAUTION
18,000
+120
To avoid cracking jewels, allow
25,000
+155
mechanism to warm up at room
35,000
+205
temperature. This is best done by
u. When hot bath reading is 50 feet or more below
immersing mechanism in a bath at
cold bath reading, move each push rod to next notch in
room temperature before placing It in
compensator bracket, away from diaphragm.
hot bath.
v. If original hot bath reading is less than 50 feet
below cold bath reading pr when remaining error after
p. Remove mechanism, reset to 0 and immerse in
shifting push rods is still less than cold bath reading, turn
hot bath for five minutes. Tap frame again and record
diaphragm support nut between compensator bracket
reading.
and diaphragm, then turn second diaphragm support nut
q. If reading in hot bath does not differ from reading
in same direction.
in cold bath by more than tolerances specified in table 2-
w. When temperature compensation is completed, if
1, the temperature compensation is satisfactory and no
altimeter was placed in a liquid bath, disassemble
further adjustment is required.
mechanism and clean all parts thoroughly to remove film
NOTE
of oil, paying particular attention to hairspring.
NOTE
throughout range of an instrument with
Use of adjustable centerpiece on current
maximum allowable error at zero feet
altimeters
has
greatly
simplified
altitude: therefore, to maintain a
compensation adjustments.
New
minimum error at various altitudes, it is
centerpiece is made of beryllium copper
important to compensate diaphragm as
which is a harder material than was
near to zero error as possible.
formerly used on the old type
r. If difference in hot and cold bath readings
centerpiece and insures a more friction-
exceeds tolerance shown in table 2-1, adjustment of
free bearing surface for compensator
temperature compensator is necessary.
pins.
Compensation procedure is
s. When hot bath reading is greater than cold bath
basically the same, except now close
reading by 50 feet or more, move both push rods (pins)
adjustments are made with adjusting
between diaphragm. Move rods, one at a time, by
screw on centerpiece instead of two
grasping compensator bracket with tweezers and
locknuts which were formerly used. A
twisting lightly to spring bracket away from end of rod
rough compensation may be obtained by
while shifting rod by grasping it with another tweezer. A
positioning compensating pins
in
movement of one notch gives a correction of from 50 to
dimples of compensator. Each dimple
65 feet in the reading.
will correct an error of approximately 60
t. When original hot bath reading is less than 50 feet
feet.
By increasing angle between
above cold bath reading or when remaining error after
compensating pins and centerpiece, a
shifting push rods is still clockwise, giving a reading that
plus error can be corrected. Conversely,
is too high, turn diaphragm support nut between
a lesser angle will correct a minus error.
compensator bracket and mechanism body so it moves
If distance between dimples is too great
away from diaphragm. Turn second diaphragm support
and does not permit satisfactory
nut between compensator bracket and diaphragm
compensation, it may be further adjusted
by turning screw on centerpiece. To
correct
2-12
