1. System installation requirements
1-12
TI 30A30A10-01EN
1.4
Noise countermeasures
Noise may be induced by electromagnetic induction, electrostatic induction, or from radio waves,
lightning, inductive loads, static electricity and ground potential differences. It can be picked up
by power, signal and grounding cables, and devices. With computerized control systems, noise-
induced errors in A/D conversion or in an instruction word may lead to malfunction.
To prevent noise and electrostatic buildup, take the measures described in this section in
deciding cable type, cable routing, and grounding.
1.4.1
Noise sources and noise countermeasures
It is not easy to identify the cause of any noise-triggered errors or failures due to their lack of
reproducibility. If noise problems occur, take the following countermeasures.
The following table lists typical noise sources, symptoms of noise problems, and preventive
countermeasures.
Table Noise sources & countermeasures
Noise sources
Effects
Countermeasures
Electromagnetic induction
(magnetic field)
• Destroys magnetic disk data.
• Maintain separation from magnetic-field source.
• Shield power cables with metallic conduits.
• Shield magnetic field using ferromagnetic
substance (e.g. Permalloy).
• Use twisted-pair cables.
Electrostatic induction
• Equipment maloperation.
• Interference with signals.
• Use shielded signal cables.
• Electrically separate power and signal cables
using metallic conduits and separators.
• Lay power and signal cables which intersect at
right angles.
Lightning
• Interference with signals.
• Equipment maloperation.
• Component damage.
• Lay cables underground.
• Use optical fiber cables.
• Lay cables as close to ground as possible if the
cables cannot be laid underground.
• Install and ground arresters on field and system.
Electrostatic discharge
• Equipment maloperation.
• Electronic component deterioration,
damage.
• Paper jam.
• Discharge static electricity from operators.
• Provide proper humidity.
• Ground equipment properly.
• Use antistatic floor material and clothing.
Inductive load open/close
• Spike noise interference to power
and signal lines.
• Add spark-killer to noise source.
• Separate laying of cables.
Radio (electric field)
• Equipment maloperation.
• Interference with signals.
• Use devices (transceivers, mobile phones,
smartphones, etc.) that transmit radio waves
away from the system so as not to exceed the
electric field specifications.
Ground potential difference
• Equipment Maloperation
(noise imposed on signal lines)
• Avoid multipoint grounding of signal cable.
Feb. 26, 2018-00
