MIL-PRF-39035 Resistor, Variable, Nonwirewound \(Adjustment Type\), Nonestablished Reliability, And Established Reliability, General Specification ForThis specification covers the general requirements for nonestablished reliability \(non-ER\) and established reliability \(ER\), multiturn lead-screw actuated, and single-turn, nonwirewound, variable resistors with a contact bearing uniformly over the surface of the entire resistive element, when positioned by an actuator. These resistors are capable of full-load operation \(when the maximum resistance is engaged\), at a maximum temperature of 150 Degrees C, with a resistance tolerance of ??10 percent. The ER resistors will have life failure rate levels ranging from 1.0 to 0.001 percent per 1,000 hours \(see 1.2.1.5\). These failure rate levels are established at a 60 percent confidence level maintained at 10 percent producer\'s risk on the basis of the life tests.

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MIL-PRF-39035E

TABLE XII. Resistance-temperature characteristics.

Temperature

Sequence

in OC (� 3OC)

25 1/

2 2/

-15

-55

25 1/

5 2/

150

This temperature shall be considered

the reference temperature for each of

the succeeding temperatures.

Not applicable in conformance

inspection.

Note: At the option of the manufacturer, the reverse sequence may be as follows:

� 3OC

150

� 3OC

-25

� 3OC

-55

4.8.15 Moisture resistance (see 3.20). The resistors shall be tested in accordance with method 106 of

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

Mounting: Resistors shall be clamped or otherwise mounted with terminals exposed on a stainless-steel

panel of sufficient size to extend beyond the resistor extremities, and in such a manner as to allow

electrical connections to be made to the terminals.

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

specified in 4.8.5.1.

Polarization and loading voltage: The resistors shall be divided into two equal groups; one group shall be

subjected to polarization and the other group to load.

(1) Polarization: During steps 1 to 6 inclusive, a 100 volt dc potential shall be applied with the positive

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

mounting plate.

(2) Loading voltage: During the first 2 hours of steps 1 and 4, a dc test potential equivalent to 100

percent rated wattage shall be applied to the resistors.

Test procedure: The moisture resistance cycling requirements shall be as follows: For qualification

inspection - 20 cycles; For group B inspection - 10 cycles. Every 6 months, the group B quarterly test

shall be - 20 cycles.