Advantech TPC-651H-E Series, Руководство пользователя

Страница: 25 / 68

17 TPC-651T/TPC-651H User Manual
Chapter 2
S
ystem
Setup
2.5 Power/Digital Ground and Earth Ground
The purpose is to block all the external interference on the chassis, and prevent any
possibility of bad grounding design to cause electric shock of people. This is so called
level 1 isolation which consumer PC do not implement this kind of design.
 TPC Chassis and Earth (Power pin3) are short,
 TPC Chassis and Power / Digital GND are OPEN
The TPC is and industrial grade product, designed to prevent external interference
and the possibility of electric shock. To complete the isolation design, we need to
consider the following:
 The Ethernet is isolated, a LAN connection will not impact the isolation design.
 For general USB devices, to solve EMI and ESD issues, they are designed as a
chassis and digital short. But the TPC prevents damage to USB devices, ESD
and EMI solutions are designed to use the Power GND as a vent path to ensure
Power GND and Chassis GND will not have potential difference abnormalities.
 For COM ports, since there are different COM port designs, long distance con-
nection cause voltage level difference between the two COM port chassis.So
the shell ground of cable must be isolated to signal digital ground
In real cases, many customers may break the level 1 isolation by 3rd party Device or
cable design, in this situation, we need to consider making all the GND short (Power
GND/Digital GND/Earth GND), and ensure customers have good Earth GND connec-
tion.