MIL-PRF-39015E
4.8.4.3 End resistance. The contact arm shall be positioned at the extreme counterclockwise limit of
mechanical travel, and the resistance shall be measured as specified in 4.8.4 between the contact arm
and the corresponding end terminal. The contact arm shall be positioned at the extreme clockwise limit
of mechanical travel, and the resistance shall be measured as specified in 4.8.4 between the contact arm
and corresponding end terminal. During this test, precaution shall be taken to insure that rated current of
the resistance element is not exceeded. Clockwise or counterclockwise signifies the direction of rotation
of the lead screw when the resistor is viewed from the screw head (see 3.10.3).
4.8.5 Immersion (not applicable to "L" type terminal) (see 3.11). The surface of the resistor shall be
cleaned of any foreign matter immediately before immersion.
a. Precondition: Precondition resistors in an oven at 125șC ±5șC for 13 minutes ±2 minutes, or use a
fluorocarbon bath maintained at 125șC ±5șC for a period of one and one-half minutes ± one-half
minute. Upon completion of precondition, allow resistors to stabilize to room temperature for
approximately 13 minutes ±2 minutes.
b. Immersion: Immerse resistors (not to exceed 30 samples) into a bath of fluorocarbon held at
85șC +5șC, -0șC for a period of 60 seconds ±5 seconds. The resistor shall be completely
submerged in the bath with no part at a depth of less than 1 inch. Resistors shall be shaken for a
maximum of 5 seconds and shall remain in the bath for a period of 1 minute ±5 seconds. Visually
examine resistors for inadequate seals, as evidenced by a continuous stream of bubbles
emanating from any concentrated point on the resistor.
c. Dye penetrant: A 5 piece sample of the product exhibiting inconclusive evidence of compliance to
immersion requirements (see 3.11) shall be preconditioned in an oven stabilized at 125șC ±5șC for
13 minutes ±2 minutes, or preconditioned in a fluorocarbon bath maintained at 125șC ±5șC for 1
minute ±5 seconds and immediately upon removal (within 5 seconds) shall be submerged in a dye
penetrant solution for 30 seconds minimum. The dye penetrant solution shall consist of 0.1 gram
per liter, or equivalent, of a solution stain dye such as crystal violet dissolved in deionized water
maintained at room ambient temperature. Upon removal from the dye solution, the sample shall
be held at room ambient temperature. Upon removal from the dye solution, the sample shall be
held at room temperature until external surfaces are dry. The sample shall then be carefully
opened and examined under 10X to 30X for evidence of the dye penetrant into the sealed cavity.
Evidence of such penetration verifies loss of immersion seal and lack of such evidence verifies
compliance to the requirements.
4.8.6 Continuity (see 3.12). The lead screw actuator shall be rotated at a uniform rate such that the
wiper traverses the effective electrical travel in both directions within 1.250 minutes. During rotation a
electrical device shall be connected between the wiper and either end terminal and monitored for smooth
and directional change in voltage or resistance. Precaution shall be exercised to prevent excessive
current flow in the resistor during test. There shall be no ohmmeter discontinuity upon reversal of
direction of lead screw (see 3.12).
4.8.7 Actual effective electrical travel (see 3.13). The actual effective electrical travel, which is the
number of turns of the lead screw in which a change in contact arm position gives a measurable change
in voltage output, shall be measured by placing the resistor in a device and circuit which will indicate both
mechanical position of the lead screw and voltage output.
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