MIL-PRF-39002 Resistors, Variable, Wirewound, Semi-Precision, General Specification ForThis specification covers the general requirements for semi-precision, wirewound, variable, resistors having a resistance element of wire, wound on an arc shaped insulated form, so that a contact bears uniformly on the resistance element, when adjusted by a contact shaft. The electrical output \(in terms of percent of applied voltage\) is linear with respect to the angular position of the contact arm. These resistors are capable of full-load operation \(when the maximum resistance is engaged\) at a maximum ambient temperature of 85 Degrees C, and are suitable for continuous operation, when properly derated, at a maximum temperature of 135 Degrees C. These resistors have a tolerance of ??5 percent.

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MIL-PRF-39002C

FIGURE 3. Peak noise measuring circuit.

4.6.7 Dielectric withstanding voltage (see 3.12).

4.6.7.1 At atmospheric pressure. Resistors shall be tested in accordance with method 301 of MIL-STD-202. The

following details shall apply:

Special preparation: Resistors shall be mounted on metal plates of sufficient size to extend beyond the

resistor extremities, and in such a manner that measurements can be made between the terminals tied

together and any other external metal parts.

Magnitude of test voltage: 900 V rms.

Nature of potential: From an alternating current (ac) supply at commercial-line frequency and waveform.

Points of application of test voltage: Between the terminals connected together and all external metal

portions of the resistors and metal-mounting plate.

Examinations and measurements: During the tests, the leakage current shall be monitored and the resistors

examined for evidence of arcing and breakdown. At the conclusion of the test, resistors shall be examined

for evidence of damage.

4.6.7.2 At reduced barometric pressure. Resistors shall be tested in accordance with method 105 of

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

Method of mounting: As specified in 4.6.7.1a.

Test condition letter: D.

Period of time at reduced pressure prior to application of potential: 1 minute.

Tests during subjection to reduced pressure: A potential of 250 volts rms from an ac supply at commercial-

line frequency and waveform shall be applied for 1 minute.

Points of application: As specified in 4.6.7.1d.

Examinations and measurements: As specified in 4.6.7.1e.