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

RX:

Test specimen.

Oscilloscope bandwidth:

100 Hz to 50 kHz.

Minimum input impedance:

At least 10 times the nominal resistance being tested.

NOTE: At the calibration of the decade, terminals 1 and 2 must be coincident. Calibration decade is to be set for the

contact-resistance (CRV) level of the specified nominal resistance being tested.

FIGURE 3. Contact resistance variation measuring circuit.

4.8.5 DC resistance (see 3.11). Resistors shall be tested in accordance with method 303 of MIL-STD-202. The

following details shall apply:

Measuring apparatus: Different types of measuring test equipment (multimeters, bridges, or equivalent)

are permitted to used, provided the equipment is the same model, or if it can be shown that the

performance of the equipment is equivalent to or better.

Test voltage: Measurements of resistance shall be made by using the test voltages specified in table XI.

The test voltage chosen, whether it be the maximum or a lower voltage which would still provide the

sensitivity required, shall be applied across the terminals of the resistor. This same voltage shall be used

whenever a subsequent resistance measurement is made.

TABLE XI. DC resistance test voltage. 1/

Total resistance, nominal

Maximum test voltage

(in ohms)

(in volts)

10 to

100

Incl.

1.0

over

100 to

1,000

Incl.

3.0

over

1,000 to 10,000

Incl.

10.0

over

10,000 to

0.1 megohm Incl.

30.0

over 0.1 megohm

100.0

The critical resistance value is the maximum standard resistance

value which will dissipate full wattage when the maximum continuous

working voltage is applied.