STP-iX455/iXL455 Series Instruction Manual
9-6
Operation
9.2.6 Recommended items about communication cable installation
Noise generated by many factors such as the type or length of cable, communication
speed, and different communication devices may cause the communication failure with a
serial port. It is very difficult to prevent a communication failure completely. The
followings are valid methods to countermeasure against a noise for the communication
cable.
Use a shield type product for communication cable, and an EMI countermeasure product for
the communication connector hood. Choose the suitable grounding method according to the
operating environment.
[Both ends grounding (Electromagnetic shielding)]
The grounding method for reducing the inducted voltage produced in the communication
line by the magnetic field emitted from a power supply line. Shield both ends are
grounded by all the cables of connected communication device. Clamp the STP pump
side shield on a connector hood. A ground loop will be made up through both ends
grounding. Connect between GND of a STP pump and PC with low impedance to
prevent ground potential difference.
SIM
Signal
line
GND
PC
Signal
line
GND
prevent ground potential difference
Shield
Figure 9.3 Grounding example (Both ends grounding)
[Single point grounding (Electrostatic shield)]
This is the grounding method for reducing the electrostatic induction produced in the
communication line by the exogenous noise caused by electrostatic induction or
unnecessary radiation. Ground the communication cable shield by single point to the PC
side. DO NOT ground on STP pump side. When ground potential difference is high, the
single point grounding may be more effective than both ends grounding against a noise.
Shield
Signal
line
Signal
line
GND
Figure 9.4 Grounding example (single point grounding)
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