Quantcast Ground System Noise Current

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(2)  A pair of heavy-duty spring clip leads for connection between the bridge and the bonded
junction. Clip leads may be connected to braided straps and plugs to make connection to the bridge. Total
resistance of external connectors and leads should not be greater than 0.001 ohm.
Equipment Setup.
Using the heavy-duty spring clips and braids or low resistance wire, connect the leads to the
Place the bridge in operation according to the manufacturer's operating manual.
(3)  Zero the bridge, including leads, and connect the clip-leads across the bonded junction as
shown in Figure 2-12. By placing the current leads away from the junction while placing the potential leads
near the junction, the effects of the probe contact resistance are minimized. However, if the bond to be
measured is internal to a metallic grid such that other current paths exist between the current probes in
parallel to the one through the bond under test, the potential and current probes should be connected near to
the same point (one potential probe and one current probe on each side of the bond). Otherwise, a gross error
may result. When multiple parallel paths exist, this procedure may not adequately indicate the true condition
of the specific junction under interest, but it will indicate the total resistance between both sides of the
Test Procedure.
Adjust the bridge balance until a null is obtained.
Record the indicated resistance. Ground System Noise Current. This test procedure measures the stray currents on fault protection
subsystem, signal grounds, and cable shields which are frequent causes of common-mode noise interference
within a facility.
Equipment Required.
Oscilloscope (battery operated, if available).
(2) Oscilloscope current probe.
(3) Oscilloscope camera.


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