Page 251 - belden

TE CH N I C A L INF O RM A T I O N 251

Shielding
Shield Types Application Guide, Relative Cost Comparison of Shield Types
Shield Performance Ratings

Shield Types Application Guide

Choose a Foil Shield… Relative Cost Comparison
• For protection against capacitive (electric Relative cost comparisons are based on
field) coupling where shield coverage is coaxial cable. Chart shows relative shield
more important than low DC resistance.
cost as one component of the total cost
• When possible sources of interference of the cable. These cost ratings may
include TV signals, crosstalk from other change depending on the physical
circuits, radio transmitters, fluorescent construction of the cable.
lights or computing equipment.
• For MATV, CATV, video, networking, 5
computer I/O cables in office, industrial
or commercial environments where 4
ambient EMI levels are low.
Choose a Braid Shield… 3
• For superior performance against diffusion
coupling, where low DC resistance 2
is important, and to a lesser extent,
capacitive and inductive coupling.
1
• When possible sources of interference
exhibit low impedance characteristics,
0
such as motor control circuits and switches Braid Spiral Foil Foil/Braid Duobond Plus ® Quad
which operate inductive loads.
Shield Performance Comparison Chart
• For computer to terminal interconnect
for process, instrumentation or Cable Shield Rating ®
Frequency Range
control applications. and Types of Braid Foil/Braid/Foil
Interference Anticipated 95% Coverage Spiral Foil Foil/Braid Duobond Plus ®
Choose a Spiral Shield…
• For functional shielding against diffusion Frequency: DC
and capacitive coupling at audio Capacitive A AA AAA AAA AAA
frequencies only.
Diffusion AAA A C AAA AAA
• When possible sources of interference Diffusion/Inductive — — — — —
are power lines and fluorescent lights. Diffusion/Inductive/Capacitive — — — — —
• For applications when flexibility and Frequency: 15 kHz
flex life are major concerns, such as Capacitive A AA AAA AAA AAA
microphone and audio cables and Diffusion AAA B C AAA AAA
retractile cords.
Diffusion/Inductive AA C A AA AAA
Diffusion/Inductive/Capacitive — — — — —
Choose a Combination Shield…
Frequency: 10 MHz to 1000 MHz
• For shielding against high frequency
Capacitive A AA AAA AAA AAA
radiated emissions coupling and ESD.
Diffusion — — — — —
Combines the low resistance of braid
and 100% coverage of foil shields. Diffusion/Inductive B C A AA AAA
Diffusion/Inductive/Capacitive B C A AA AAA
• When possible sources of interference
include radio transmitters, TV stations, * Although ratings shown above are based on shielded coaxial cable test results, these ratings
also pertain to shielded multi-conductor and flat cable where shield types are available.
printed circuit boards, back planes, motor Shield Rating Key
Note: Shield effectiveness decreases as frequency increases. Therefore, ratings in one
control circuits and computing equipment. frequency category do not imply equal shield effectiveness in other frequency categories. AAA Best
• For Video, CATV, MATV, networking, AA Better
computer I/O cables and computer- A Good
aided manufacturing applications. B Functional
C Unsatisfactory
Technical Information
— Not Applicable

Fo r m o r e i n fo r m at i o n, c o n t a c t Be ld e n Te ch n i ca l S u ppo r t : 1- 8 0 0 - B E L D E N -1 • www. b e l d e n . c o m