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

3.6 Voltage rating. The theoretically calculated rated continuous working voltage or the voltage equivalent to

power rating (rated wattage) shall be determined from the following formula:

E =

Where:

E = Rated or root mean square (rms) continuous working voltage.

P = Power rating.

R = Nominal total resistance.

3.7 DC resistance.

3.7.1 Total resistance. When measured as specified in 4.6.2.1, the total direct-current (dc) resistance shall not

deviate from the specified nominal resistance (see 3.1) by more than �5 percent.

3.7.2 Absolute minimum resistance (not applicable to style RK09). When measured as specified in 4.6.2.2, the

absolute minimum resistance shall not exceed 0.5 percent of the nominal total resistance value, or 1 ohm, whichever

is greater.

3.7.3 End resistance. When measured as specified in 4.6.2.3, the end resistance shall not exceed 3 percent of the

nominal total resistance value, or 1 ohm, whichever is greater.

3.7.4 Resistance value deviations. All maximum deviations as specified in this section are to be considered

absolute limits with the exception of the contact resistance adjustment.

3.8 Continuity. When resistors are tested as specified in 4.6.3, the change in voltage or resistance shall be

unidirectional throughout the effective electrical travel.

3.9 Mechanical travel. When resistors are tested as specified in 4.6.4, the mechanical travel shall be as specified

(see 3.1).

3.10 Actual effective-electrical travel. When resistors are tested as specified in 4.6.5, the actual effective electrical

travel shall be as specified (see 3.1).

3.11 Peak noise. When resistors are tested as specified in 4.6.6, the peak-noise resistance shall not exceed 500

ohms, with the following exceptions:

In group I of table II:

Shall not exceed 100 ohms.

Shall not exceed 100 ohms.

In group III of table II

Shall not exceed 200 ohms.

3.12 Dielectric withstanding voltage. When resistors are tested as specified in 4.6.7, there shall be no evidence of

damage, arcing, or breakdown; the leakage current shall not exceed 1 milliampere.

3.13 Independent linearity tolerance. When resistors are tested as specified in 4.6.8, the initial tolerance shall not

exceed �3.0 percent for style RK09 and �1 percent for all other styles.

3.14 Insulation resistance. When resistors are tested as specified in 4.6.9, the insulation resistance shall be not

less than 1,000 megohms.

3.15 Torque.

3.15.1 Starting. When resistors are tested as specified in 4.6.10.1, torque required to affect rotation shall be 0.5

ounce-inch to 6 ounce-inches.