MIL-PRF-94 Resistors, Variable, Composition General Specification ForThis specification covers the variable resistors having a composition resistance element shaped in an arc, and a contact bearing uniformly thereon, so that a change in resistance is produced between the terminal of the contact and the terminal of either end of the resistance element when the operating shaft is turned. These resistors are capable of full load operation \(where maximum resistance is engaged\) at a maximum ambient temperature of 70 degrees C and are capable for continuous operation when properly derated, at a maximum temperature of 120 degrees C \(see 6.9\).

Pages 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10

MIL-PRF-94G

3.4.6.2 Standard bushings. When standard bushings are specified, the bushing shall be as shown for the

applicable style of resistor (see 3.1).

3.4.6.3 Locking bushings. When locking bushing are specified, the bushing shall be as shown for the applicable

style of resistor (see 3.1).

3.4.6.4 Shaft and panel seal bushings. When shaft and panel seated bushings are specified, the panel seal may

be an integral part of the resistor or may be detachable (see 3.1).

3.4.6.5 Nonturn device. A nonturn device shall be furnished on resistors, which will prevent their rotation with

respect to the surface on which they are mounted. The location of the nonturn device and its widest dimension shall

be as specified (see 3.1). If the nonturn device is not symmetrical about its vertical axis, it shall be so placed that a

plane passes perpendicular to the widest dimension and through its center shall pass through the axis of the

operating shaft, and shall be an integral part of the resistor or permanently attached thereto.

3.4.7 Securing of screws, nuts, and threaded parts. All screw-thread assemblies shall be made resistant to

loosening under vibration.

3.4.8 Enclosure. Resistors shall have enclosures for protection against mechanical damage.

3.5 DC resistance (see 4.7.2).

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

absolute limits with the exception of the contact resistance adjustments.

3.5.2 Total resistance. Resistors shall have a total resistance equal to the nominal resistance value plus or minus

the resistance tolerance specified (see 1.2.1.6, 1.2.1.7, and 4.7.2.1).

3.5.3 Resistance taper. A linear taper is one having constant change or resistance with angular rotation. The

resistance taper shall conform in general shape to the normal curves shown in figure 3 and figure 4, as applicable.

Resistance measurements shall fall within �20 percent of the nominal values shown by curves at the specified angle

of 50 percent of electrical rotation (see figures 3 and 4, and 4.7.2.2).

3.5.4 Minimum resistance (see 4.7.2.3).

3.5.4.1 Taper A (linear) resistors. The minimum resistance at either extreme of the electrical rotation shall not

exceed the values listed in table VI.

TABLE VI. Minimum resistance taper (taper A).

Total

Maximum value of

resistance

minimum resistance

ohms

750 incl

5 1/

1,000

to 10,000 incl

15,000

to 50,000 incl

75,000

to 0.1 megohm

Megohms

0.15 to 0.25 incl

125

0.35 to 0.50 incl

250

0.75 to 1.00 incl

500

1.50 to 2.50 incl

1,000

3.50 to 5.00 incl

1,500

1/ Applicable to all styles except RV6. For values of RV6, see 3.1.