MIL-PRF-49052G
3.7 Reliability. The assembly shall have a mean time to failure of not less
than 2000 hours when operated under the reliability test conditions specified
herein. The reliability test shall be conducted on assembly(s) in which the
entire assembly useful cathode area shall be directly illuminated with a target
brightness adjusted to achieve an equivalent photocathode illumination at levels
corresponding to a T/1.58 objective lens. The target brightness source shall be
located 20 inches from the front of front of the assembly(s) under test. The
target shall have a color temperature of 2856 K and completely fill the field-of-
view of the monocular under test. The target brightness shall be 1 x 10-4 foot-
lamberts (fL), which shall be raised to 5 x 10-3 fL for 5 seconds and to 50 fL for
3 seconds once during each on-period. Sufficient instrumentation shall be
provided to ensure immediate recognition of a catastrophic failure as well as a
change in relative output brightness. In addition, the assembly(s) shall be
subjected to the environmental conditions of Table V listed below. On-off
cycling shall consist of 55 minutes of on-time followed by 5 minutes of off-time.
Input voltage to the assembly shall not be less than 2.7 Vdc nor more than 3.0
Vdc. The initial brightness gain of each assembly shall be between 7,500 and
15,000. Acceptable limits of brightness gain during and at the completion of the
test shall be 5,000 to 20,000. No gain adjustment shall be allowed during the
test or inspections. Signal-to-noise ratio shall not be less than 3.5 during
this test or any inspection. The assembly parameters: luminance gain; EBI;
signal-to-noise ratio; photocathode, microchannel plate, and screen quality;
output brightness uniformity; and useful cathode diameter shall be tested at
room temperature as specified herein once each 200 hours ± 50 of operating time.
Reliability test assemblies shall be removed from the test condition for not more
than 15 hours for measurement of assembly parameters. At other times, assemblies
shall be cycled continuously on a 24 hour basis. A failure shall be presumed to
have occurred immediately after the last successful measurement or inspection
unless acceptable continuous monitoring instrumentation records the actual time
of failure. Failed assemblies which have been removed from the test shall not be
replaced; a failed assembly repaired and returned to the test shall be used for
information only.
Table V.
Reliability test environmental conditions.
Parameter
Environmental Conditions
40 C ± 5C
O
O
Temperature
Temperature cycling
Not applicable
Vibration
2.2 g ± 10% peak acceleration at any non-resonant
frequency between 20 Hz and 60 Hz measured at
mounting points on the equipment. The duration
of vibration shall be at least 10 minutes
during each period of equipment on-time.
3.8 Identification and marking. The assembly shall be identified and
serialized in accordance with drawing SM-D-657310. The marking shall include a
coded acceptance date such that the first two numbers shall be the last two
digits of the year, and the last two numbers shall be two digits indicating the
calendar week of the year (01 through 52). Reading from left to right or top to
bottom, the code number shall indicate the year and week of acceptance, in that
order.
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