FED-STD-228A
Method 6041.1
18 APRIL 2014
SURFACE RESISTANCE, FINISHED WIRE AND CABLE
1. SCOPE
1.1 This method is intended for use in determining the surface resistance of the wire or cable. This test
is not required for shielded wire.
2. SPECIMEN
2.1 The specimen should consist of a 6-inch length of finished wire or cable. In the sampling operation
and subsequently until completion of the test, this specimen should be handled with maximum care to
avoid even the slightest contamination, especially with regard to the surface area which will be under test.
If cleaning of the specimen is appropriate, it should be cleaned by a distilled water wash, followed by an
isopropyl alcohol wash and a second distilled water rinse, dried carefully in an air oven, and handled
subsequently with maximum care as previously directed.
3. APPARATUS
3.1 The apparatus shall be as follows:
3.1.1 A test chamber capable of maintaining a temperature of 25° ± 1°C and an internal relative humidity
of 95 ± 4 percent. A recommended chamber may be formed from a tightly-covered rectangular glass
vessel containing an ample reservoir of saturated aqueous solution of chemically pure potassium
sulphate (see ASTM E104). The chamber should be instrumented to measure the relative humidity within
the chamber, with the humidity indication visible from outside the chamber. All instrumentation through-
leads into the chamber should be suitably protected where they enter the chamber, to prevent
introduction of any error in the specimen measurements. The electrical resistance of the chamber
measured across each pair of lead wires with no specimens in place, shall be not less than 1 million
megohms. This measurement should be made after the chamber has been closed and conditioned for 96
hours at 95 ± 4 percent relative humidity and a temperature of 25 ± 1°C.
3.1.2 A DC. voltage source preferably a battery of dry cells, that will supply a voltage of not less than 200
nor more than 500 volts.
3.1.3 A standard resistance scale, and shunts of any suitable pattern.
3.1.4 A suitable instrument for measuring the current that will give an accuracy of within 10 percent and a
sensitivity of 1 percent of full scale deflection.
3.1.5 A galvanometer, of fairly high sensitivity and having the following qualifications, has been found to
meet the accuracy required. The galvanometer constant shall be not less than 50,000. The means for
indicating the deflection shall produce a sharply outlined indication on the scale, and the deflection shall
be not less than 100 divisions (measured from zero) when the variable shunt has been set to determine
the constant of the galvanometer. The resistance of the shunts and the calibrating resistor shall be
checked from time to time.
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