MIL-PRF-29C
4.7.4 DC resistance.
4.7.4.1 Qualification inspection. Resistors shall be tested in accordance with method 303 of MIL-STD-202.
(see 3.11) The following details shall apply.
a.
Limit of error of measuring apparatus: 0.1 percent, maximum.
b.
Test voltage: 100 volts dc, maximum.
4.7.4.2 Conformance inspection. A dc supply of twice the rated voltage specified (see 3.1) shall be applied to the
resistors for a period of 1 second. Resistors shall then be subjected to the test specified in 4.7.4.1.
4.7.5 Short time overload. Resistors shall be measured for dc resistance as specified in 4.7.4. A dc supply of
twice the rated voltage specified (see 3.1) shall then be applied to the resistors for a period of 30 minutes in free
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space and still air at an ambient temperature of 25 C. Thirty minutes after removal of potential, resistors shall again
be measured for dc resistance as specified in 4.7.4. At the end of this test, resistors shall be examined for evidence
of arcing, burning, or charring, or other damage. (see 3.12)
4.7.6 Temperature rise. A dc supply of the rated voltage specified (see 3.1) shall be applied to the resistors while
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maintained in an oven in free space and still air at a temperature of 85 C. The hot spot temperature shall be
determined after a period of 2 hours, using the thermocouple method with a thermocouple having wires no larger in
diameter than 0.010 inch (0.25 mm) (No. 30 AWG). Resistors shall be horizontally mounted during this test with the
thermocouples junction resting on the hot spot and the thermocouples wires hanging down on opposites sides of the
resistor. Weights of at least 2 ounces on each lead shall provide the pressure of the thermocouples junction against
the surface of units under test. (see 3.13)
4.7.7 Resistance temperature characteristics. Resistors shall be tested in accordance with method 304 of
MIL-STD-202. (see 3.14) The following details shall apply:
a. Reference temperature: Room ambient temperature.
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b. Lowest and highest test temperature: -55 C, +110 C
4.7.8 Thermal shock. Resistors shall be measured for dc resistance as specified in 4.7.4 and then placed in an
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oven which has been heated to a temperature of 85 C. A dc supply of the rated voltage specified (see 3.1) shall be
applied to the resistors for a period of 1 hour. Within 5 seconds after removal of potential, resistors shall be removed
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from the oven and plunged into tap water at a temperature of 0 C. After 5 minutes, resistors shall be removed from
the bath and the surface moisture removed. One hour after removal from the bath, the dc resistance shall again be
measured as specified in 4.7.4 and compared with the initial resistance value. The resistors shall then be examined
for evidence of chipping, crazing, cracking, or spalling of the exterior coating or enclosure, and for other mechanical
damage. (see 3.15)
4.7.9 Salt water immersion cycling. Resistance shall be subjected to a total of five daily cycles as specified in
4.7.9.1. Each daily cycle shall be followed by a conditioning period wherein the resistors are maintained, without
load, at temperature of 25 C ±5 C for a period of not less than 12 hours nor more than 24 hours. Testing may be
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discontinued at any time resistors change in resistance more than that allowed by the applicable requirements.
(see 3.16)
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