MIL-PRF-22097 Resistors, Variable, Nonwirewound, Adjustment Type, General Specification ForThis specification covers the general requirements for multi-turn lead screw actuated and single turn nonwirewound, variable resistors with a contact bearing uniformly over the entire surface of the entire resistive element, when positioned by the actuator. These resistors are capable of full load operation \(where maximum resistance is engaged\) at a maximum ambient temperature of 70 Degrees C and 85 Degrees C, and are capable for continuous operation when properly derated, at a maximum temperature of 125 Degrees C and 150 Degrees C \(see figure 1\). These resistors have a resistance of ┬▒10 percent \(see 3.1\).

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MIL-PRF-22097J

3.4.7.2 Stops (applicable to single turn units, unless otherwise specified) (see 3.1). Stops employed to limit the

mechanical rotation of the contact arm assembly may be part of, but shall not complete an electrical circuit

3.5 Power rating. The resistors shall have a power rating based on continuous full load operation at the ambient

temperature specified for the applicable characteristic (see 3.1 and table I). The power rating is dependent on the

ability of the resistors to meet the life requirements specified in 3.20. For temperatures in excess of those specified,

the load shall be derated as shown on figure 1. Power ratings as specified (see 3.1) are applicable only when the

maximum resistance is engaged in the circuit. When only a portion of the resistance element is engaged in the

circuit, the power rating is reduced in approximately the same proportion as the resistance.

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

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

E = PR

Where:

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

P = Power rating.

R = Nominal total resistance.

The rated voltage shall not exceed the maximum continuous working voltage (see 3.1).

3.7 DC resistance (see 4.6.2).

3.7.1 Total resistance. When measured as specified in 4.7.2.1, the total direct-current (dc) resistance shall not

deviate from the specified nominal resistance (see 3.1) by more than �10 percent.

3.7.2 End resistance. When measured as specified in 4.7.2.2, the end resistance for all characteristics shall not

exceed 20 ohms, or 2 percent of the total resistance, whichever is greater.

3.7.3 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 Actual effective electrical travel. When resistors are tested as specified in 4.7.3, the number of turns of the

operating shaft necessary for the contact arm to traverse the resistance element shall be as specified in (see 3.1).

3.9 Contact resistance variation. When measured as specified in 4.7.4, the contact resistance variation shall not

exceed the applicable value specified in table I.

3.10 Dielectric withstanding voltage. When resistors are tested as specified in 4.7.5, there shall be no evidence of

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

3.11 Insulation resistance. When resistors are tested as specified in 4.7.6, the insulation resistance shall not be

less than 1,000 megohms.

3.12 Torque.

3.12.1 Operating. When resistors are tested as specified in 4.7.7.1, the torque required to move the contact arm

shall be as specified (see 3.1).

3.12.2 Clutch (applicable only to multiturn lead screw actuated units, unless otherwise specified). When resistors

are tested as specified in 4.7.7.2, the contact arm shall idle against the stop without electrical discontinuity or

evidence of mechanical damage. The travel of the contact arm shall be capable of reversing direction.