MIL-PRF-22684F
4.6 Methods of inspection.
4.6.1 Visual and mechanical inspection. Resistors shall be examined to verify that the materials, design,
construction, physical dimensions, marking, and workmanship are in accordance with the applicable requirements
4.6.2 DC resistance (see 3.7). Resistors shall be tested in accordance with method 303 of MIL-STD-202. The
following details and exceptions shall apply:
a. Measuring apparatus: Different types of measuring test equipment (multimeters, bridges, or equivalent) are
permitted to be used on the initial and final readings of this test, provided the equipment is the same style,
model, or if it can be shown that the performance of the equipment is equivalent or better.
b. Measurement energy: The measurement energy applied to the unit under test shall not exceed 10 percent of
the 25oC rated wattage times 1 second.
c. Temperature: The dc resistance test specified in group 1 of table II shall be performed at 25°C ±2°C. For all
other tests, unless otherwise specified herein, the temperature at which subsequent and final resistance
measurements are made shall be within ±2°C of the temperature at which the first resistance measurement
was made.
4.6.3 Thermal shock (see 3.8). Resistors shall be tested in accordance with method 107 of MIL-STD-202. The
following details and exceptions shall apply:
a. Special mounting: Resistors shall be mounted by their terminals so that there is at least 1(25.4 mm) inch of
free air space around each resistor and the mounting is in such a position with respect to the air that it offers
substantially no obstruction to the flow of air across and around the resistors.
b. Test condition letter: A, except that 125°C +3°C, -0°C (150°C +3°C, -0°C for qualification only) shall be used.
c. Measurements before and after cycling: DC resistance shall be measured as specified in 4.6.2, prior to the
first cycle and 1 hour after completion of the fifth cycle and stabilization at room temperature.
d. Examination after test:: Resistors shall be examined for evidence of mechanical damage.
4.6.4 Low-temperature operation (see 3.9).
a. Mounting: As specified in 4.6.3a.
b. Procedure: Following the final measurement of dc resistance specified in 4.6.3c, the resistors shall be placed
in a cold chamber at room temperature. The temperature shall be gradually decreased to -65°C +0°C, -5°C,
within a period of not less than 1 hour 30 minutes. For conformance inspection only, and at the option of the
manufacturer, the resistors may be placed in the cold chamber when the chamber is already at the extreme
low temperature. After 1 hour of stabilization at this temperature, the full rated continuous working voltage
(see 3.1) shall be applied for 45 minutes. The resistors may be loaded individually or in parallel. Fifteen
minutes, +5 minutes, -0 minutes after the removal of voltage, the temperature in the chamber shall be
gradually increased to room temperature within a period of not more than 8 hours. The resistors shall be
removed from the chamber and maintained at a temperature of 25°C ±5°C for approximately 24 hours; the dc
resistance shall then be measured as specified in 4.6.2. Resistors shall then be examined for evidence of
mechanical damage.
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