(5) Use the adjusting disk on the dial to set the aneroid to the
exact station pressure. This disk should not be used for large adjust-
(6) The tip of the pointer should clear the dial by at least 1/ 16
inch. If it does not, very carefully spring the pointer upward until
this clearance is obtained.
(7) Replace the plastic window, screws, washers, and cover.
c. Placing mechanism in new case.
Note. The mechanisms and dials of Barometers ML-102-D and ML-316/TM are
not interchangeable, since each aneroid mechanism is hand-calibrated with its par-
ticular dial, but the complete mechanism, with dial, may be placed in a new case.
Before placing in a new case, however, check the instrument against an accurate
mercury barometer and apply the linkage test (par. 20c (3) ), to make sure the
interior mechanism is functioning properly. A barometer that is in error by 3 milli-
bars, or more, should be replaced. Ordinarily anything that would damage the case
sufficiently to require it to be replaced would also damage the mechanism. If the
case is replaced in the field, it must be done only by qualified personnel.
(1)Remove the cover and plastic window according to instructions
(2) By means of the rubber mounts in the two rear corners, care-
fully lift the dial and mechanism assembly from the case. Be extremely
careful not to damage the corrugated cell and the pointer during this
(3) Holding the dial and mechanism assembly by the rear rubber
mounts, fit the two front rubber mounts into the front corners of the
new case. (Avoid striking the cell against the metal stop in the front
righthand-corner.) Now ease the dial to a level position, being sure
the rubber mounts are resting against the stops in the four comers.
(4) Replace the plastic window, screws, washers, and cover.
d. Adjusting rack and pinion (fig. 11).
Caution: Occasionally, following a severe shock, the barometer may
show an error of 10 millibars. This may indicate that the rack and
pinion have jumped a tooth. In this event, send the barometer to the
Signal Corps depot where it will be adjusted by qualified personnel.
Do not attempt this adjustment in the field!
(1) The distance between teeth is equal to 10 millibars on the scale.
Look closely and note that there are three prick punch marks on the
rack between the teeth. There is also one prick punch mark on one
of the teeth of the pinion (fig. 11).
(2) The distance between two punch marks on the rack is equal
to one complete revolution of the pinion. When the teeth are properly
meshed, the punch mark on the pinion should be directly opposite one
of the punch marks on the rack as shown in figure 11.
(3) If the punch mark on the pinion is out of mesh with the punch
mark on the rack, swing the vertical stop (fig. 11) away from the rack
90 to the right or left, with the aid of a small pair of pliers. Gently
raise the rack above the pinion and rotate the pinion until the punch
marks line up. Allow the rack to return to it. normal position and
replace the stop in its original position.
24. LUBRICATION. The mechanism
not require oil. Oil would only interfere with the proper functioning
of the instrument and thereby introduce serious errors in reading.
DO NOT USE OIL ON THE MECHANISM!