MIL-PRF-49465 Resistor, Fixed, Metal Element, Power Type, Very Low Resistance Values, General Specification ForThis specification covers the general requirements for power type, low value \(1 ohm and below\), fixed resistors \(2 terminal and 4 terminal\) for use in electrical, electronic, communications, and associated equipment. Included are precision resistors of ??1 percent, ??3 percent, and ??5 percent initial resistance tolerances with power ratings ranging from 3 watts to 5 watts at +25 degrees C derated to 0 power at +275 degrees C.

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MIL-PRF-49465C

4.8.10 Insulation resistance (see 3.16). Tests shall be made in accordance with method 302 of MIL-STD-202 with

the following exceptions:

Test condition: A.

Special preparation: In accordance with 4.8.9.1a.

Points of measurement: In accordance with 4.8.9.1g.

4.8.11 Moisture resistance (see 3.17). Resistors shall be tested in accordance with method 106 of MIL-STD-202.

The following details and exceptions shall apply:

Mounting: Soldering by their leads to rigid mounts or terminal lugs. The spacing of the mounts or terminal

lugs shall be such that the length of each resistor lead is approximately .375 inch when measured from the

edge of the supporting terminal to the resistor body. One half of the sample units shall be covered with a

V-shaped metal strap whose width is equal to the length of the resistor body as indicated on figure 2. The

strap shall be made of a corrosion resistant metal and shall be kept in contact with the resistor body by

supporting the body as indicated on figure 2, with a nonconducting, noncorrosive support whose width is

less than that of the body and which will not act as a moisture trap. For group B inspection, each half of the

sample shall be apportioned as three highest values, two lowest values for a total of five sample units per

half. The mounting straps may be individual for each resistor, or continuous for all resistors.

Mounting (special body configuration): If the procedure in 4.8.11 does not lend itself to the body

configuration, special details shall be as specified in the associated specification (see 3.1).

Initial measurement: Immediately following the initial drying period, dc resistance shall be measured as

specified in 4.8.2 at test conditions specified in 4.3.1.

Polarization and loading voltage:

(1)

Polarization voltage: During steps one to six inclusive, a 100 V dc potential shall be applied only to

those resistors which have a polarizing strap. This potential shall be applied with the positive lead

connected to the resistor terminals tied together, and the negative lead connected to the polarizing

straps.

(2)

Loading voltage: During the first 2 hours of steps one and four, a dc test potential equivalent to 100

percent rated wattage shall be applied to those resistors which do not have the polarizing strap

specified in 4.8.11a.

Subcycle: Step 7b shall not be applicable. Step 7a shall be performed during any five of the first nine

cycles only.

Final measurements: Upon completion of step six of the final cycle, the resistors shall be held at the high

humidity condition and a temperature of +25 C �2 C for a period of 1 hour 30 minutes to 3 hours 30

minutes. Resistors shall then be removed from the chamber, and within 30 minutes, the dielectric

withstanding voltage (atmospheric), insulation resistance, and dc resistance tests shall be performed as

specified in 4.8.9, 4.8.10, and 4.8.2, respectively. The same straps used for polarizing the resistors may

also be used for the dielectric withstanding voltage and insulation resistance tests.

Examination after test: Resistors shall be examined for evidence of mechanical damage.