MIL-DTL-12211G
4.8.6 Vibration resistance.
4.8.6.1 Vibration class, 1. To determine conformance to 3.5.6.1, the switch shall be mounted in a test
fixture simulating actual mounting in use and shall be connected in a series circuit with a 24 V (nominal)
power source and applicable indicating lamp. Care shall be taken to see that the mounting is free of
resonance over the frequency range. While energized, the switch shall be subjected to a simple
harmonic motion having an amplitude of .03 inch (0.7 mm) or 50 g's peak, whichever is less. Tolerance
of + 10 percent is permissible for the amplitude. The vibrational frequency shall be varied over the range
from 10 to 3,500 Hz. Rate of frequency shall be logarithmic. When there is no provision for logarithmic
cycling, other automatic cycling rates of frequency change may be used. The vibrational cycle from 10 to
3,500 and back to 10 Hz shall be accomplished in 20 + 2 minutes. This scanning cycle shall be repeated,
and checked. After the scanning cycles, the switch shall be vibrated at the critical frequency for 2 hours.
If there is more than one critical frequency, the 2-hour period shall be divided equally between the critical
frequencies. If there are more than three critical frequencies, the three most critical shall be selected and
the switch vibrated for 40 minutes at each of the frequencies selected. If no critical frequency is
identified, the specimen shall be vibrated at 50 g's acceleration, with frequency cycled from 10 to 3,500
and back to 10 Hz. Rate of change of frequency shall be logarithmic, or where there is no provision for
logarithmic cycling, other automatic cycling rates of frequency change may be used. Time for each cycle
shall be 20 + 2 minutes. Duration of the test shall be 2 hours (6 complete cycles). The following test
conditions shall apply: The load shall be that specified in 3.3.2. A pressure of 10 psi above the upper
actuation pressure specified on the applicable MS standard or drawing shall be applied to type I switches.
A pressure 10 psi below the lower actuation pressure specified on the applicable MS standard or drawing
shall be applied to type II switches. The indicating lamp shall be observed periodically during the test for
evidence of circuit closure. After the test, switches shall be examined for defects specified in 3.5.6.1.
This test procedure shall be accomplished along each of three mutually perpendicular axes. Total
vibrating time shall be 9 hours (3 hours along each axis).
4.8.6.2 Vibration class 2. To determine conformance to 3.5.6.2, the switch shall be mounted in a test
fixture simulating actual mounting in use and shall be connected in a series circuit with a 24 V (nominal)
power source and applicable indicator. Care shall be taken to see that the mounting is free of resonance
over the frequency range. The switch shall then be subjected to the vibration test described in test
condition A, method 204 of MIL-STD-202. The following test conditions shall apply: The load shall be
that specified in 3.3.2. A pressure of 10 psi above the upper actuation pressure specified on applicable
MS standard or drawing shall be applied to type I switches. A pressure of 10 psi below the lower
actuation pressure specified on the applicable MS standard or drawing shall be applied to type II
switches. The indicating lamp shall be observed periodically during the test for evidence of circuit
closure. After the test, switches shall be examined for defects specified in 3.5.6.1.
4.9 Endurance. To determine conformance to 3.6, the switch shall be connected to the lamp load
current specified in 3.3.2 and to a variable pressure fluid supply line. The switch shall then be cycled,
10,000 times, from 0 psi to twice the upper actuation pressure specified on the applicable MS standard or
drawing, and back to 0 psi. During the test, the switch shall be observed periodically for evidence of
malfunction.
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