MIL-DTL-26126C
4.6 Methods of examination and test.
4.6.1 Visual and mechanical examination (external). Relays shall be examined to verify that the
materials, external design and construction, physical dimensions, marking, and workmanship are in
accordance with the applicable requirements (see 3.1, 3.3, 3.4, 3.7, and 3.9).
4.6.2 Dielectric withstanding voltage (see 3.5.1). A potential of 1,000 V rms, 60 Hz, shall be applied
for 60 seconds, or 1,200 volts for 1 second between terminals and case.
4.6.3 Calibration (see 3.5.2).
4.6.3.1 Pickup voltage (see 3.5.2.1). A voltage of 28 V dc shall be instantaneously applied to the S
and G terminals. The voltage shall be slowly increased (without interruption of voltage) up to 31 V, after
which the voltage increments and rate of increase shall be .25 V, steps 5 to 10 seconds apart.
4.6.3.2 Time-voltage characteristics (see 3.5.2.2). The relay shall be tested to determine that the
normally open contacts close within the time limits specified by the time-voltage curves shown on figure 1.
For routine testing only, the relay shall be tested with the relay axis horizontal. A voltage of 28 V shall be
applied to the coil terminals for a minimum of 2 seconds. The voltage shall be instantaneously raised to
the overvoltage values shown on figure 1. After each overvoltage step, the relay shall be completely de-
energized for at least 2 seconds before the next overvoltage step is taken. The relay shall be tested at 35,
40, 50, 60, and 75 V. An oscillograph, electronic timer, or other suitable timing device acceptable to the
acquiring activity, shall be used to determine the time delay. Three readings at each voltage shall be
obtained.
4.6.4 Endurance (see 3.5.3). The relay contacts shall be connected to the load as specified in the
applicable specification sheet. The relay's case shall be connected to the power supply ground or
negative, with a normal blow fuse rated at 150 V dc, 100 milliamperes. The relay shall be operated at 40
V dc for 15,000 cycles at the rate of 10 cycles per minute. The current shall be on for 3 seconds and off
for 3 seconds. The relay contacts shall be monitored during each cycle. A miss shall be defined as failure
of the contacts to make positive contact as checked by automated test equipment or failure of the case
fuse.
4.6.5 Overload (see 3.5.4). The relay shall be tested as specified in 4.6.4 except for the following:
Total test cycles - 40; input voltage - 150 V dc; timing cycle - 2 cycles, 5 seconds apart. Each pair of
cycles shall be spaced 55 seconds apart.
4.6.6 High temperature (see 3.5.5). The relay shall be subjected to an ambient temperature of 71°C
±2°C for 5 hours with 30 V applied to the S and G terminals. At the end of this period and with the relay at
the stated temperature, the unit shall be tested to the requirements of 3.5.2. At not less than 6 hours after
the high-temperature test, the relay shall be resubjected to the tests specified in 3.5.2. During the high
temperature test, temperature measurements shall be conducted on all electrical connections to
resistor(s) within the relays which have soldered connections.
4.6.7 Low temperature (see 3.5.6). The relay shall be subjected to a temperature of -55°C ±2°C for 5
hours. At the end of this period with the relay at the stated temperature, 28 V dc shall be applied to the
relay coil for 2 minutes before taking the time-voltage characteristic. The test shall be accomplished in a
minimum amount of time to prevent heating of the coil above the temperature reached in the 2 minute
heating period. The tests specified in 4.6.3 shall be conducted at the end of the low temperature soak
(while at low temperature). Tests specified in 4.6.3 shall be repeated after the unit has been temperature
stabilized at room temperature.
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