S9407-AB-HBK-010 Datasheet, PDF (116/276 Pages) Glenair, Inc. – HANDBOOK OF SHIPBOARD ELECTROMAGNETIC SHIELDING PRACTICES

S9407-AB-HBK-010, Rev. 2
6.4 CABLE CATEGORIZATION
6.4.1 Table of Cable Categories and Designators
The cable categories, category descriptions, group numbers, and cable designators are listed
in table 6-1. Note that the cable designator consists of a cable category and, in most cases, a group
number.
6.4.2 Selection of Cable Designators
The selection of cable designators should reflect actual cable characteristics and operating
parameters. The cable category descriptions given in table 6-1 do not completely describe all
possible functions, therefore, a reasonable amount of analysis and judgement is required in selecting
the proper designator. As an example, a cable used in a dc control circuit employed to switch a logic
gate should be categorized as an R-8 (cables used to carry digital data), and not an R9-1 (cables that
carry dc). Using the R-8 category cables, the gate switching function is protected against electric field
interference by an overall cable braid. This would not be the case were it categorized R9-1 and an
unshielded power cable used as the transmission line.
The selection of a cable designator that provides greater than necessary protection is
unwarranted because it places prohibitive spatial restrictions on adjacent cables.
6.5 PARAMETERS AND CONSIDERATIONS FOR CABLE SPACING REQUIREMENTS
6.5.1 Effective Loop-Area Parameter
The susceptibility of a cable to magnetic fields if proportional to its effective loop area (see
paragraph 6.1b) which can be determined from the geometric and electrical properties of the cable.
The equation used to determine effective loop area (A) is presented here for reference.
A=
e _ind
square inches ,
0.40 6fB
where:
eind = induced voltage in microvolts
f = frequency in hertz
B = flux density in gauss.
The data for determining effective loop area is obtained by measuring the voltage induced
(eind) in a fixed length of cable placed in the calibrated field (B) of a Helmholtz coil energized at a
frequency (f). The resulting information is used to assign cable categories to the individual cables.
Tabular data that lists cables and their assigned categories and group numbers are provided in figures
6-1 through 6-5.
6.5.2 Self-Compatibility of Cable
It is assumed throughout this section that functions within multiconductor cables will be
compatible. A multiconductor cable should not contain radiator and susceptor functions which must
operate simultaneously if any spacing of those functions is required by Figure 6-6. If no spacing is
required by Figure 6-6, and if the susceptor functions are contained in shield braid for protection from
electric-field coupling, the functions should be compatible.
6-3