MIL-PRF-22885H
4.7.26 Sand and dust (when specified) (see 3.1 and 3.31). Switches shall be tested in accordance with method
110 of MIL-STD-202. The following details apply:
The second 6-hour test at 63°C (145° F) shall be performed immediately after reaching stabilization in step
a.
2.
b.
During exposure to sand and dust, the switches shall be mechanically operated at a frequency of 60 cycles
± 5 cycles per minute for 2,500 cycles.
c.
Post test examination: Switches shall be examined for operating characteristics and circuit continuity.
4.7.27 Overload cycling (see 3.32). Each switch to be tested for electrical endurance shall first be tested for
overload cycling at room ambient conditions, using the same voltage, electrical frequency, and the same pairs of
contacts that will subsequently be used for the electrical endurance test. The switches shall close and open the
overload current of a resistive circuit equal to 150 percent of the resistive load rating at the particular voltage and
electrical frequency. The cycling rate shall be five cycles to six cycles of operation per minute (see 6.4.12). Fifty
cycles of operation shall be performed. The duty cycle shall be approximately 50 percent on, 50 percent off.
4.7.28 Electrical endurance (see 3.33). Switches shall make and break the specified electrical load for 25,000
cycles of operation (see 6.4.12) unless otherwise specified (see 3.1). The cycling shall be continuous, except at the
option of the contractor, cycling may be interrupted after each 5,000 cycles of operation (see 6.4.12). The test
sample shall have two lines of legend, block characters, .09 inch to .12 inch (2.29 mm to 3.05 mm) high, which utilize
at least three-fourths of the maximum horizontal length of the legend area. Following the test, the switches shall be
examined for damage and legibility of the legend.
4.7.28.1 Conditions.
Unless otherwise specified (see 3.1), test loads shall be arranged so that an independent load shall be
a.
provided for each pole.
b.
Switches shall be continuously monitored and recorded to determine whether any contact has failed to open
or close its individual circuit in the proper sequence. The monitoring circuit shall not shunt inductive
components of inductive loads or switch contacts.
Temperature rise shall be measured (see 4.7.28.3).
c.
d.
The duty cycle shall be approximately 50 percent on and 50 percent off for resistive, inductive, and motor
loads. The duty cycle shall be approximately 30 percent on and 70 percent off for lamp loads.
e.
The cycling rate shall be 10 cycles to 12 cycles per minute.
f.
When applicable, half of the switches shall be normally open types and the other half shall be normally
closed types. For double throw switches, one-half of the switches shall be tested with the load circuit
connected to one throw, and the remaining half of the switches shall be tested with the load circuit
connected to the other throw.
g.
In any of the specified load tests, each conductor shall be of an applicable size for single use in free air as
listed in table XIV. If the switch rating under test does not coincide with a wire size, the next larger diameter
wire shall be used.
h.
One side of the power supply, one side of the test load, the switch mounting plate, metal case (if applicable),
and the actuating member, if metal, shall be connected to a common ground.
i.
All lamps (or LED's when specified, see 3.1) shall be continuously energized at their maximum rated voltage
during cycling. MS3338-6839 or MIL-DTL-6363/8-5 lamps (or industry equivalent) or industry lamp number
86 shall be used, as applicable.
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