Quantcast Shielding - hdbk419a_vol20238

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Using the test procedure described in Section measure the stray current levels on a selected
number of shields surrounding sensitive signal cables, on conduit, on the signal reference subsystem, and on
equipment ground cables.  Document the test details (i.e., vertical sensitivity and sweep rate) on the
photographs made of the oscilloscope displays and attach the photographs to the Survey Form.
Using the test procedure described in Section perform differential noise measurements
between interfaced equipments: between the lower frequency (or other) signal ground network and structural
ground; between widely separated points on ground networks; between signal grounds in equipments and the
point of connection to the earth electrode subsystem; and between any other two points where common-mode
voltages are causing system or equipment noise problems.
Determine the type of grounding required, i.e., single-point or equipotential ground plane.
f. Shielding.
Identify the presence and nature (or type) of shields at the facility. (Recognize that shielding may
be incidentally provided by a wall, screen, or other type of barrier that is primarily intended for a different
purpose.) Describe the shields in Section A, Part VII of the Form.
Inspect screens, shielded cabinets, doors, covers, etc., of all designated rf barriers for wear,
damage, corrosion, broken bond straps, broken or damaged bonds, and loose gaskets. Observe equipment
operation for evidence of interference, noise, or malfunctions. Record deficiencies in Section B of Part VII.
Ensure that grounding conductors passing through a designated rf barrier are bonded to that barrier,
Be sure that the bonds and bonding inspection (Section includes the shields.
Examine cables and connectors for broken or frayed shields, improper mounting, and evidence of
corrosion.  Check to see if the termination of cable shields is in accordance with Sections and Note deficiencies in Section C of Part VII. Test Procedures. Bond Resistance.
This test is intended to give a general indication of bond adequacy, based on the
dc resistance of the bond.
Equipment Requirements. The equipment required for this test is as follows:
(1)  A dc resistance bridge capable of measuring to about 0.001 ohm or better. The bridge should
be portable and not be position-sensitive. Connection of the test sample to the bridge terminals should be
easily performed without cumbersome adapters or special tools.  An instrument with separate potential
(voltage) and current terminals is preferred to a two-terminal device.


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