MIL-C-793B(Ord)
4.3.1 General. -The environmental tests specified shall be limited to
those contained in this paragraph. Three of the first five drive controllers
and one out of every additional one hundred or fraction thereof shall be tested
4.3.2 Temperature. - The drive controller shall be exposed to an
air temperature of minus 62.2° C (-800 F) for a period of 3 days. The air
temperature shall then be raised to minus 31. 6°C (-25°F) and after the
internal temperature of the unit has reached equilibrium (approxima tely
4 hours), it shall be tested for conformance with the performance require-
ments of this specification. The air temperature shall be raised to plus
71° C (+160° F) and after the internal temperature of the unit has reached equil-
ibrium at that temperature it shall be allowed to remain at that temperature
for a period of 4 hours. The air temperature shall be reduced to plus
51.50 C (+ 125° F) and after the internal temperature of the unit has reached
equilibrium at that temperature, the top surface shall be exposed to 360 BTU/Ft.
Sq/Hr., for a period of 4 hours. The unit then shall be tested for conform-
ance with the performance requirements of this specification.
4.3.3 Humidity .- A test chamber that is capable of being sealed
shall be used; The source of heat shall be arranged in such a manner that
the radiant heat will not fall upon the drive controller being tested. A unit
shall be placed in the chamber, the temperature of which is adjusted to
plus 46.1° C ± l.l° C (+ 115° F 22°F) and the relative humidity adjusted to
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95:5 percent. The unit shall remain under the above conditions for a
period of 6 hours. The temperature of the chamber shall be readjusted to
plus 26.7°C ±1.1 °C (+ 80° F ±2° F) and the unit shall be allowed to remain
under this new condition for a period of 6 hours. The transitional period shall
be 2 hours; the rate of change during that period shall be uniform. The
above cycle shall be repeated ten times. Immediately afterthis test the
drive controller shall meet the requirements of 3.5.2.
4.3.4 Rain - The drive controller shall be mounted in the test chamber
to simulate installation conditions. The rain test chamber temperature shall
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be maintained between 20 C to 30°C(68° F to 86° F) throughout the test period.
A simulated rainfall of 4 + 1 inch per hour shall be produced by a suitable means
of such design that the water is emitted in the form of small droplets rather than
a fine mist.
The temperature of the water shall be maintained between
ll° C to 24°C (51.8° F to 75.2° F). The water spray shall be direction the drive
controller for a period of 2 hours in directions ranging from vertical to 45°
from the vertical. The simulated rain shall be directed on all surfacesof the
drive controller that are normally subjected to rain when the instrument is in
its operating position.
4.3.5 Vibration. - The drive controller shall be mounted rigidly using
its own mounting provisions, to simulate field use. Each unit tested shall
be vibrated successively along each of the three mutually perpendicular directions
with accelerations and excursions as shown below. Applied frequency shall be
changed at a uniform rate between the limits indicated, the rate of change shall
not exceed one cycle per second.
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