FED-STD-228A
Method 6011.1
18 APRIL 2014
RESISTANCE, ELECTRICAL, STEEL ARMOR
1. SCOPE
1.1 This method is intended for use in determining the electrical resistance of steel armor of wire and
cable.
2. SPECIMEN
2.1 The specimen should be a piece of the inspection unit at least 10 feet in length from which any
covering over the armor has been removed.
3. APPARATUS
3.1 The apparatus shall be as described in method 6021.
4. PROCEDURE
4.1 If a Wheatstone bridge is used, the resistance of the leads connecting the bridge to the specimen
shall be obtained with the leads short-circuited on themselves and the results subtracted from the
measured resistance of the specimen.
4.1.1 If the tests are conducted with a Kelvin double bridge, both current and potential leads shall be
used. The current leads shall be attached in such manner as to give assured contact with a cleaned
surface of the specimen. The potential leads should be attached by encircling clamps on the bared armor
or to a binding of fine copper wire wrapped tightly for several turns about the bared armor.
4.1.2 The test shall be made by a method using both current and potential leads if the resistance is less
than 1 ohm. Where potential leads are used, the distance between each lead and the corresponding
current lead shall be at least three times the diameter over the armor.
4.2 The length of the specimen shall be measured to an accuracy of 0.2 percent by means of the steel
scale and the value recorded as L.
4.3 The specimen between potential conductors shall be connected to the testing instrument as
described in 4.1.1. The specimen shall not be tested while it is under tension. It may be laid flat and
straight on a clean dry surface of material having low conductivity, such as paper, wood, stone, or
cement. The laboratory temperature should be as near as practicable to 20°C (68°F). If a laboratory with
temperature controlled at 20°C is not available, the specimen may be tested at room temperature. The
specimen shall be allowed to condition for at least 2 hours before testing. It shall then be maintained at
the required potential for a period of 1 minute and then the resistance measured and the value recorded
in ohms as R. At this point the temperature of the surrounding medium shall be recorded as T.
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