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

4.7.5.2 Barometric pressure. Resistors shall be tested in accordance with method 105 of MIL-STD-202. The

following details and exceptions shall apply:

Method of mounting: As specified in 4.7.5.1a.

Test condition C.

Period of time at reduced pressure to application of potential: 1 minute.

Tests during subjection to reduced pressure: Voltage as specified (see 3.1) from an ac supply at

commercial line frequency and waveform shall be applied for 1 minute.

Points of application: As specified in 4.7.5.1d.

Inspections and measurements: As specified in 4.7.5.1e.

4.7.6 Insulation resistance. Resistors shall be tested in accordance with method 302 of MIL-STD-202 (see 3.11).

The following details shall apply:

Test condition: A or B, whichever is more practicable.

Special preparation: As specified in 4.7.5.1a.

Points of application: As specified in 4.7.5.1d.

4.7.7 Torque (see 3.12).

4.7.7.1 Operating. The maximum operating torque required to move the contact arm on the resistive element shall

be determined at approximately 10 percent, 50 percent, and 90 percent of the actual effective electrical travel by the

torque wrench or by any other method acceptable to the Government (see 3.12.1).

4.7.7.2 Clutch. The contact arm shall be adjusted to each extreme limit of mechanical travel, and sufficient torque

shall applied to the operating shaft actuator. During idle, a electrical indicating device connected between the contact

arm terminal and the adjacent end terminal shall be observed for electrical continuity. After idle, the operating shaft

shall be rotated in the opposite direction and the indicating device observed to determine if the contact arm reversed

4.7.7.3 Stop. Resistors shall be mounted by their normal mounting means. The contact arm shall then be rotated

to each extreme limit of mechanical rotation, and the specified torque (see 3.1), applied through the operating shaft to

the stop (see 3.12.3).

4.7.8 Thermal shock. Resistors shall be tested in accordance with method 107 of MIL-STD-202 (see 3.13). The

following details and exceptions shall apply:

Test condition B.

Measurement before cycling: Setting stability and total resistance shall be measured as specified in 4.7.8.1

and 4.7.2.1, respectively. Continuity of the contact arm shall be verified by connecting a vacuum tube

voltmeter or other indicating device, between the contact arm terminal and the counterclockwise end

terminal. The applied voltage shall be in accordance with table XI.

Inspection after test: Resistors shall be inspected for evidence of mechanical damage (see 3.13).