MIL-PRF-25435D
4.5.14 Humidity. Nonhermetically sealed transmitters shall have pressure and power
connections made to simulate operational conditions and shall be connected to the standard
indicating unit. The transmitter shall be placed in the test chamber at ambient temperature and
humidity. The chamber temperature shall gradually be raised to 150°F and the humidity to 95%
over a 2-hour period. This temperature and humidity shall be maintained for 6 hours. After 6
hours, the humidity shall be maintained at a minimum of 85% and the test chamber temperature
shall be reduced from 150° to 85°F over a 16 hour period. The above temperature and humidity
cycle shall be repeated 10 times (240 hour test). Immediately after completion of this test, the
transmitter shall be subjected to the dielectric strength test (4.5.2) and the scale and friction error
test (4.5.3).
4.5.15 Salt fog. A 50-hour salt fog test shall be performed in accordance with ASTM B117.
Any trace of corrosion or mechanical failure constitutes a cause for rejection.
4.5.16 Fungus. Nonhermetically sealed transmitters and any required lubricants shall be
subjected to a fungus resistance test for a minimum of 28 days and a maximum of 84 days
depending on the degree of certainty required in determining the existence or effect of fungal
growth. The transmitter shall be configured as it would be during shipping, storage, and service.
The test temperature shall be between 75° and 90°F with 95% ± 5% relative humidity. At least
five different species of fungus shall be used. Additional fungi may be used based on prior
knowledge of specific material deterioration characteristics. Any trace of fungus, degradation,
corrosion, or mechanical failure constitutes a cause for rejection.
4.5.17 Electromagnetic interference. The transmitter shall comply with the requirements of
MIL-STD-461 for Air Force Aircraft. The minimum tests required are CE102, CS101, CS114,
CS115, CS116, RE102 and RSE103.
4.5.18 Power. Proof of compliance with MIL-STD-704 shall be provided.
4.5.19 Vent boss and connector strength. The transmitter shall be secured to a fixture by the
engine mount connection on the transmitter. A bending moment of 25 foot-pounds shall be
applied at the vent boss and then the electrical connector about any axis perpendicular to the
longitudinal axis of the transmitter. There shall be no evidence of the transmitter calibration
shifting-out-of tolerance, distortion of the base plate, damage to vent boss and electrical
connector welds, or damage to electrical connector soldering. The transmitter shall be subjected
to the sealing test (4.5.5.1 or 4.5.5.2). The transmitter then shall be subjected to the scale and
friction error test (4.5.3).
4.5.20 Damping. The transmitter shall be placed in a test fixture with the pressure connection at
the bottom, the vent at the top, and the electrical connector connected to the standard indicating
unit. Oil conforming to MIL-PRF-7808, with a viscosity of 2,500 centistokes at -65°F, shall be
brought to a pressure that produces full scale deflection of the indicating unit. The pressure then
shall be released and the time required for the change from full scale deflection to 14% of full
scale deflection shall be 2 ± 1 second.
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