MIL-DTL-17896E
3.6. Reflector or spacer ring. The reflector or spacer ring, if used, shall be of formed,
drawn, or spun metal with white enamel finish or with the same finish as the dial. The reflector
or spacer ring shall fit or be held snugly.
3.7 Indicating hands.
3.7.1 Index hand. The index hand shall be of rigid metal construction with black lacquer
finish and centered with relation to the dial and dial graduations. The method of attachment
shall be such that the index hand can be easily removed yet will not be accidentally loosened or
shifted in position by vibration or jarring. The end of the pointer shall extend more than half
way over the smallest graduation on the outer scale but not beyond the longest graduation on the
outer scale. The breadth of the hand at the end near the graduations shall be such as to facilitate
accurate readings.
3.7.2 Set hand. The set hand shall be of brass or stainless steel, clear lacquered and shall
be of the same general width as and concentric with the index hand. The assembly shall be
moisture and dust resistant and shall eliminate movement of the hand by vibration under service
conditions specified in 3.9 and when tested in accordance with 4.6.5.
3.8 Aneroid mechanism. The aneroid mechanism shall consist of an evacuated metal
cell or cells that are sensitive to variations in atmospheric pressure. The cell or cells shall be
connected with the index hand by the necessary series of levers, sector racks, pinions, pivots, or
linkage chains in such a manner that variations in atmospheric pressure shall be transmitted to
the index hand from the cells. The aneroid mechanism shall be mounted on a frame or base plate
that can be attached to the case and removed easily for the purpose of adjustment and calibration.
3.8.1 Position compensating. The aneroid mechanism shall be accurately balanced or
counter-balanced to withstand the test of 4.6.7.
3.8.2 Mechanical stops. Mechanical stops shall be provided to keep the cell or cells
from damage when subjected to one half inch of mercury pressure over the upper range and one
half inch of mercury pressure below the lowest range of the barometer.
3.9 Service conditions. The barometer shall operate under any of the following service
conditions.
a.
Ambient, low, and high temperature compensation.
b.
Shock.
c.
Vibration.
d.
Salt fog.
3.10 Accuracy and calibration. The accuracy and calibration of the barometers shall be
such as to withstand the tests specified in 4.6.8 through 4.6.10.
3.11 Drift. The barometer shall be guaranteed to withstand aging effects for a period of
one year, and recalibration at the end of the first six months shall agree with the original
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