MIL-DTL-24643C
4.9.8.4 Observation. Specimen failure shall be construed if the voltage source overload relay trips prior to
removal of the test voltage from any specimen connection. If the insulation resistance test is specified (see 3.1),
then the specimen shall be retained for use in that test.
4.9.9 Jacket flaws. One hundred percent of all finished cables with overall shields shall be subject to the spark
test in accordance with Clause 900 of UL Standard 1581 at 3kV rms.
4.9.10 Conductor and shield continuity. One hundred percent of all finished cable shall be tested for continuity
prior to shipment. To establish continuity, not more than 25 volts DC shall be applied across each conductor and
shield of the cable through an appropriate indicator, such as an ohmmeter, light, or buzzer. The test voltage may be
applied to conductors and shields individually or in series.
4.9.10.1 Observation. Specimen failure shall be construed if the specimen exhibits an open electrical circuit.
4.9.11 Surface transfer impedance. The surface transfer impedance characteristics of the overall cable shield of
finished cable shall be tested in accordance with NEMA WC 61, and as specified in 4.9.11.1. The electromagnetic
pulse (EMP) response of the cable shield shall be determined in accordance with 4.9.11.2.
4.9.11.1 Cable sample preparation. The individual shields of shielded components, when present, shall be
connected to the conductors and the connected conductors and shields shall be the conductor as specified in
NEMA WC 61.
4.9.11.2 Determination of EMP response. The surface transfer impedance determined as specified shall be
known over the frequency range DC to 100 MHz. Zt shall be assumed constant in the frequency range DC to 0.1
MHz. The EMP response in dB shall be determined as follows:
[
]
[Z t ( f )]2
⎡10
⎤
8
EMP response = (-185) 10 log ⎢ ∫ 2
df ⎥
(
)(
)
α + f 2 β2 + f
2
⎢0
⎥
⎣
⎦
surface transfer impedance at frequency f (Ω/m)
Zt(f) =
Where:
α
2.39 × 105
=
β
4.12 × 107
=
f
=
frequency (Hz)
df =
decade of frequency
The integral expression may be approximated by a summation if at least 100 points per decade of frequency are
used.
4.9.11.3 Observation. Specimen failure shall be construed if the surface transfer impedance is greater than
specified (see 3.1) or if the calculated EMP response of the overall cable shield is less than specified (see 3.1).
4.9.12 Swept electrical parameters. Completed cable shall be tested in accordance with TIA/EIA-568-B.2 for
transmission performance characteristics as specified in the applicable specification sheet. This standard specifies
the appropriate measurement procedures and formulas for a four pair balanced cabling system for all transmission
parameters.
4.9.12.1 Specimen. The specimen shall consist of a length of finished cable 328 feet in length. Every pair shall
be tested for basic electrical and swept electrical parameters as specified in the appropriate specification sheet.
4.9.13 Stress resistance. Cable resistance to stress imposed during shipboard installation shall be determined as
specified in 4.9.13.1 through 4.9.13.6.1. Cable stress is the result of, but not limited to, tensile strain imposed by
pulling; crushing forces imposed by cable clamps, straps, stuffing tubes, and multi-cable transits; bending forces
imposed by routing; and twisting of the cable subcomponents due to re-spooling.
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