MIL-R-19365 Resistor, Adjustable, Wirewound, PowerThis specification covers power, adjustable, wirewound, resistors for use in electrical, electronic, communication, and associated equipment. These resistors have a resistance range of 1 ohm to 15,000 ohms, inclusive, and a resistance tolerance of ┬▒5 percent. The power ratings cover a range of 11 watts to 210 watts, inclusive. These power ratings are applicable only when the maximum resistance is engaged in the circuit. When only a portion of the resistance element is engaged, the power rating is reduced in approximately the same proportion as the resistance.

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MIL-R-19365E

TABLE X.  Resistance temperature characteristic test ambient temperatures.

1/  This temperature shall be

considered the reference for each succeeding temperatures.

4.7.3.2  Product acceptance inspection.  Resistors shall be tested as specified in 4.7.3.1, except that sequences 1,

2, 3, and 7 of table X shall be performed only, in that order.

4.7.4  Temperature (see 3.9).  Resistors shall be placed in an oven at room temperature.  The temperature of the oven shall then be elevated gradually to the maximum hotspot surface temperature of the resistor +5OC, -0 OC

(see table I).  The period of the transition from room temperature to the hotspot surface temperature shall be

accomplished in not more than 45 minutes.  For conformance inspection, at the option of the manufacturer, the resistors may be placed in an oven whose temperature has already been brought up to approximately the hotspot

surface temperature.  The resistors shall be conditioned at the latter temperature for a two hours.  They shall then be

allowed to cool gradually to room temperature, after which they shall be visually examined for evidence of mechanical damage.

4.7.5  Dielectric withstanding voltage (see 3.10).  Resistors shall be tested in accordance with method 301 of

MIL-STD-202.  The following details shall apply:

a.        Special preparations: Resistors shall be mounted, without supplementary insulation, between two metal plates normal to the longitudinal axis of the resistor, one plate at each end, held firmly against the end of the resistor core by a through bolt.  These plates shall be of sufficient size to extend beyond the resistor terminal extremities.  The adjustable terminal shall be positioned within ±5 percent of the electrical center.

b.    Magnitude of test voltage:  1,000 volts.

c.    Nature of potential:  Alternating current (ac) supply at commercial line frequency and waveform.

d.        Points of application of test voltage:  Between the terminals tied together, and the mounting hardware and plates.

e.        Examination and measurements:  Total resistance shall be measured before and after the test.  At the conclusion of the test, resistors shall be examined for evidence of mechanical damage, arcing, and insulation breakdown.

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