MIL-DTL-8777F
4.6.4.10.2 Procedure. The specimen shall be placed in the test chamber and the temperature and
relative humidity raised to the specified values and maintained for 6 hours. At the end of the 6-hour
period, the heat shall be shut off. During the following 16-hour period, the temperature shall be reduced
to not greater than 38°C. At the end of the 16-hour period, heat shall again be supplied for an additional
2-hour period and the temperature stabilized to 71º ±2°C. This cycle shall be repeated a sufficient
number of times to extend the total time of the test to 360 hours (15 cycles).
4.6.4.10.3 Insulation resistance measurements. Insulation resistance measurements shall be made
with the external surface of the wire grounded and the conductor remaining at elevated potential. The
insulation resistance shall be determined after 1-minute electrification with a direct-current potential of
250 to 500 volts. Where the wire is shielded, connections shall be made at the shielding and the
conductor. Unshielded wires shall be submerged in a 5% solution of NaCl and H2O. The insulation
resistance measurements test shall be conducted at 22° ±3°C.
4.6.4.11 Insulation resistance. A 52-foot specimen with its center 50-foot section shielded as specified
in MIL-PRF-7808, but with not less than 95 percent coverage, shall be coiled and suspended in a gravity-
convection type air oven adjusted to 200° ±5°C and held for 100 hours. At the end of this period and
while at this temperature, the insulation resistance shall be measured between the conductor and the
shield.
4.6.4.12 Surface resistance. Specimens shall consist of 6 inch lengths of finished wire and provided
with two 0.25 inch (6.35 mm) ring type metal foil electrodes, or for small wires, several turns of fine tin
coated copper wire, spaced 1.0 inch (25.40 mm) apart between the nearest edges near the center of the
specimen length, wrapped snugly around axis of the specimen and bound with the takeoff leads for
electrical testing of surface between the electrodes. After conditioning these specimens for 96 hours at a
relative humidity of 95 ±5 percent and a temperature of 25° ±5°C, the resistance between the electrodes
shall be measured using a dc potential of 200 to 500 volts while the specimens are still within the
conditioning chamber and after a 1 minute electrification. The surface resistance shall be computed by
multiplying the measured resistance value by the measured overall diameter of the specimen in inches.
Following the initial resistance measurement, the potential specified in the applicable MS sheet shall be
applied between the electrodes for 1 minute. After a discharge interval of 15 to 20 minutes following the
potential test, the surface resistance shall be remeasured and computed.
4.6.4.13 Smoke. This test shall be performed in still air at normal room temperature. A specimen of
the wire approximately 15 feet long shall be so suspended that a section no less than 10 feet long is
horizontal and unsupported. One end of the wire shall be suitable weighted in order that no sagging will
occur throughout the test. An electric current shall be applied to the wire, and the voltage drop measured
over the 10-foot portion. From the current and voltage values, the resistance of the cable shall be
calculated. The temperature of the cable conductor shall be determined from the change in resistance.
The current shall be so adjusted that the conductor temperature stabilizes at 210° ±5°C. This conductor
temperature shall be maintained for 15 minutes. A flat black background shall be used.
4.6.4.14 Wire weight. The weight of each lot of finished wire shall be determined by procedure I of
4.6.4.14.1. Lots failing to meet the wire weight requirements of 3.4.3.2 when tested as specified in
procedure I shall then be submitted to procedure II of 4.6.4.14.2, and all reels or spools failing to meet the
weight requirements of 3.4.3.2 shall be finally rejected. Group I sampling shall not apply to procedure II.
4.6.4.14.1 Wire weight procedure I. The length of a specimen at least 10 feet long shall be
accurately measured with the resultant measurement transposed to pounds per 1,000 feet.
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