FED-STD-228A
4. PROCEDURE
4.1 The 6-inch specimen shall be provided, near its center, with two electrodes spaced 1.0 inch apart
between their nearest edges. Each electrode shall be composed of several turns of fine (AWG 27 or
finer) tin-coated copper wire, wrapped snugly around the circumference of the specimen, leaving a free
end of the fine wire of sufficient length for soldering to electrical lead wires. With the specimen and
electrodes thus prepared, the electrodes shall be soldered to lead wires in the test chamber, the test
chamber shall be closed, and the test assembly shall be conditioned for 96 hours at the specified relative
humidity and temperature. The surface resistance between the electrodes shall be measured with a DC
potential of not less than 200 volts nor more than 500 volts, while the specimen is still within the test
chamber, by noting the potential and leakage current after 1 minute electrification. No temperature
correction factor shall be applied. The surface resistance computed by multiplying the applied DC.
voltage by the measured overall diameter of the specimen in inches and dividing by the leakage current in
microamperes, shall be not less than that specified in the detail specification of specification sheet.
Following the initial resistance measurement, a 2,500-volt (rms), 60 cycle potential shall be applied
between electrodes for 1 minute. There shall be no evidence of distress such as arcing, smoking,
burning, flashover, or dielectric failures. After a discharge interval of 15 to 20 minutes, following the
potential test, the surface resistance shall be remeasured and shall be not less than that specified in the
detail specification or specification sheet.
5. RESULTS
5.1 Unless otherwise specified in the detail specification or specification sheet, one specimen from each
inspection unit shall be tested.
5.2 The DC potential and leakage current shall be recorded.
5.3 The surface resistance value and the remeasured surface-resistance value shall be recorded.
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