MIL-DTL-48550A
temperature for a minimum of 4 hours. At the completion of this 4 hour period, the
temperature shall then be gradually raised to +160 ± 5 °F and the collimator shall remain at
this temperature for a minimum of 4 hours. At the completion of this 4 hour period the
temperature of the test chamber shall be gradually reduced to room ambient temperature
(+60°F to +90°F) at which time the collimator shall be removed from the test chamber.
The collimator shall then meet the requirements of 3.4.2 through 3.8 inclusive. See 6.6,
Thermal shock. As an option, the collimator may be removed from the environmental
chamber and be inspected at the high and/or low temperature to observe the collimator's
condition if a failure is suspected.
4.4.2 Operating temperature. The collimator shall be placed in the environmental
chamber and the temperature of the chamber reduced gradually to -50 ± 5°F. The
collimator shall remain at this temperature for a minimum of 4 hours. At the completion of
this 4 hour period, and while at -50 ± 5°F, the collimator shall meet requirements of 3.7.4
through 3.7.8 inclusive. Upon completion of this portion of the test, the collimator shall
then be placed back in the environmental chamber and the temperature shall be raised
gradually to +145 ± 5°F. The collimator shall remain at this temperature for a minimum of
4 hours. At the completion of this 4 hour period, and while at +145 ± 5°F the collimator
shall again meet requirements of 3.7.4 through 3.7.8 inclusive. Upon completion of this
test, the collimator shall be returned to the environmental chamber and the temperature
shall be gradually reduced to room ambient temperature (+60°F to +90°F) at which time
the collimator shall be removed from the test chamber and then be subjected to vibration
testing per 4.4.3. See 6.6, Thermal shock.
4.4.3 Vibration. The collimator unit, enclosed in its cover with the tripod legs
secured in place, shall be vibrated while in a horizontal position at a constant frequency of
30 cycles per second with an amplitude of 1/16 inch (1/8 inch maximum excursion) for a
period of 5 minutes ± 15 seconds. Upon completion of the vibration test, the collimator
shall be subjected to a visual and tactile examination for physical failure or damage and
must meet the requirements of 3.4.4 through 3.8 inclusive.
4.4.4 Rain. The strap security test of 4.7.11 must be completed prior to this test.
The rain test chamber shall be maintained between 65°F and 90°F throughout the test
period. The collimator unit with the cover secured in place and the legs folded to the
carrying position shall be placed in the chamber and exposed to a simulated rainfall of 4 +
1 inches per hour as measured at the surface of the equipment with a U.S. Weather Bureau
type gage. The rain shall be produced by means of a water spray nozzle 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 50°F and 70°F. The rainfall shall be dispersed
uniformly over the collimator and the collimator shall be periodically rotated to allow the
simulated rainfall to contact all surfaces which are normally subjected to rain during actual
use. See 6.7 Rain test. Total duration of the rain test shall be a minimum of 2 hours.
Immediately following the rain test, the cover shall be removed and the collimator and
equipment shall be examined for evidence of water penetration or damage in accordance
with requirements specified in 3.4.4.
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