Rockwell Automation System Design for the Control of Electrical Noise - Manual (Page 117)

Publication GMC-RM001A-EN-P — July 2001
Noise Control Supplement A-15
• Segregate unshielded wires at least 150 mm (6.0 in.).
• Keep unshielded wiring as short as possible.
• Suppress the contactor coil.
• Mount all components in a shielded enclosure.
Bonding Surfaces When two or more surfaces (such as panels) require bonding, wide
flat braid is preferred to wire due to its low impedance when
compared with wire.
Wire Forms an Antenna
An efficient whip antenna for the 2 m (144 MHz) amateur radio band
is just 500 mm (20 in.) long.
An antenna has an impedance varying between 75 and 300 ohms
along its length. For bonding purposes, 300 ohms is considered much
too high.
Inductance
A flat strip is typically 1/10th the inductance of wire. However,
twisting wires together reduces inductance by more than 10x. Refer to
Figure A.14 for examples.
Figure A.14
Wire vs. flat strip inductance
150 mm Wire Loop 150 mm x 12 mm Tape Loop
1.0
µ
H
0.03
µ
H
0.07
µ
H
< 0.01 µ H