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

4.7.18 Rotational life (see 3.23).

4.7.18.1 Mounting. Resistors shall be mounted by their normal mounting means on a .625 inch (15.88 mm) thick,

glass base, epoxy laminate. The resistors shall be ganged in pairs, and each pair shall be connected in series, as

shown on figure 4, so that a nominally constant current flows through the resistors, irrespective of the contact arm

position during the tuning of the operating shaft.

4.7.18.2 Procedure. Total resistance shall be measured as specified in 4.7.2.1. A dc potential, equivalent to that

required to dissipate rated wattage across the entire resistive element of resistors having the same total resistance as

those under test, but not exceeding the maximum rated voltage, shall then be applied as shown on figure 4. The

operating shaft shall be continuously cycled through not less than 90 percent of the actual effective electrical travel, at

the rated 1 cycle for 2 minutes �0.5 minutes, for a total of 200 cycles. A cycle shall consist of travel through 90

percent of actual effective electrical travel and return to the starting point. After rotation, total resistance shall be

measured as specified in 4.7.2.1. Resistors shall then be inspected for evidence of mechanical damage.

FIGURE 4. Rotational life test circuit.

4.7.19 Terminal strength (see 3.24).

4.7.19.1 Pull (applicable to all terminal types). Resistors shall be tested in accordance with method 211 of

MIL-STD-202. The following details and exceptions shall apply:

Test condition A: Applied force : 2 pounds. Resistors clamped by the resistor body, force applied to each

lead individually.

Measurement after test: Resistors shall be inspected for evidence of mechanical damage, and tested for

electrical continuity.

4.7.19.2 Push (applicable to all terminals except type L). Resistors shall be tested in accordance with method 211

of MIL-STD-202. The following details and exceptions shall apply:

Test condition A: except force shall be applied in the direction toward the resistor body. Applied force: 2

pounds. Resistor clamped by the resistor body, force applied to each terminal individually.

Measurement after test: Resistors shall be inspected for evidence of mechanical damage, and tested for

electrical continuity.