5.2.6 Recommended items about communication cable installation
Noise generated by many factors such as types or lengths of cables, communication speed, and
other communication devices may cause communication failure with a serial port. It is very difficult to
prevent a communication failure completely. However, the followings are valid methods for
countermeasure noise for the communication cable.
• Use a shielded communication cable and an EMI countermeasure communication connector
hood. Choose the suitable grounding method according to the operating environment.
[ Both ends grounding (Electromagnetic shielding) ]
It is a grounding method for reducing an inductive voltage in the communication line produced
by the magnetic field emitting from a power supply line. Ground both ends of all the cables
connecting communication devices. Clamp the STP pump side shield on a connector hood. A
ground loop will be made up through both ends grounding. Connect between the STP pump's
GND and a PC's GND with low impedance to prevent potential ground difference.
Figure 34 - Grounding example (Both ends grounding)
[ Single point grounding (Electrostatic shield) ]
It is the grounding method for reducing an electrostatic induction in the communication line
produced by the noise from electrostatic inductions or unnecessary radiations. Ground the
communication cable shield by a single point to the PC side. DO NOT ground on the STP pump
side. When a ground potential difference is high, the single point grounding may be more
effective than both ends grounding for reducing noise.
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