MIL-PRF-26H
4.7 Methods of examination and test.
4.7.1 Visual and mechanical inspection. Resistors shall be inspected to verify that the materials, design,
construction, physical dimensions, marking, and workmanship are in accordance with the applicable requirements
4.7.2 DC resistance (see 3.6). Resistors shall be tested in accordance with method 303 of MIL-STD-202. The
following details and exceptions shall apply:
a.
Measuring apparatus: Different type 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.
Limit of error of measuring apparatus: One-fourth of the specified initial-resistance tolerance or 0.1 percent,
whichever is less, +0.002 ohm.
c.
Test voltage: Measurements of resistance shall be made by using a dc potential resulting in not more than 5
percent of rated wattage. This same voltage shall be used whenever a subsequent resistance
measurement is made.
d.
Points of application of test voltage for initial-resistance-tolerance measurement: For axial-lead resistors of
20 ohms or less, .375 ±.062 inch (9.53 ±1.57 mm) from the end of the body. For tab-terminal resistors of 20
ohms or less, locate on tab in line of hole parallel to resistor body. For all resistors above 20 ohms locate
wherever practical on lead or tab.
4.7.3 Thermal shock (see 3.7). Resistance shall be measured as specified in 4.7.2. The resistors shall then be
mounted on a rack of low-heat conducting material, and rated power shall be applied until thermal stability has been
reached. The power shall then be removed and within 8 seconds to 12 seconds, the resistors shall be subjected to
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an air temperature of -55 C +0 C, -5 C for a period of not less than 15 minutes. Measurement of resistance shall be
made not less than 2 hours after final exposure (see 4.7.2).
4.7.4 Short-time overload (see 3.8). DC resistance shall be measured as specified in 4.7.2. The resistors shall
then be mounted by means other than soldering and shall be subjected to an overload voltage that will result in 10
times rated wattage for 5 seconds or as specified (see 3.1). In no case shall this voltage exceed the value specified
(see 3.1). DC resistance shall again be measured after the resistors have cooled to room temperature.
4.7.5 Solderability (applicable to axial leads only) (see 3.9). Resistors shall be tested in accordance with method
208 of MIL-STD-202. The following details shall apply: Both leads shall be tested. The leads shall be dipped within
.062 inch (1.57 mm) of the body.
4.7.6 Terminal strength (see 3.10). Tests shall be in accordance with method 211 of MIL-STD-202 with the
following exceptions:
a.
Test condition letters A and D (pull test and twist test, respectively) for axial lead styles only.
Measurement before test: DC resistance as specified in 4.7.2.
b.
c.
Method of holding (A): Resistors shall be clamped by one terminal lead.
d.
Applied force (A): Ten pounds (or as specified) (see 3.1).
e.
For tab terminals, the resistors shall be firmly clamped and a direct pull of 10 pounds shall be applied at the
hole to each terminal, one at a time, for at least 30 seconds, in a direction away from the resistor and
parallel to the longitudinal axis.
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