Introduction; System Features - ABB S900 Manual

System features

I/O System S900 is a remote I/O system for use in hazardous areas. It
provides bus-compatible local inputs and outputs (protection IP20) for
connection of digital and analog field instruments. Due to its degree of
explosion protection it can be mounted in both hazardous areas (zone 1 and
zone 2) and safe areas.
The system consists of a mounting termination unit accommodating the
power supply units, the communication interfaces, and the I/O modules. The
passive mounting termination unit ensures power distribution and data
transfer, and also provides the connection platform. The power supply units
reliably power the entire system. One power supply unit is sufficient for
normal operation. A second (redundant) power supply unit can be added, to
improve the system availability. The communication interface controls all
data traffic between the I/O modules and the supervisory open control system
(OCS) or the programmable logical controller (PLC). The communication
interfaces CI920 can also be used in redundancy mode (line redundancy and
CI920 redundancy)
Figure 2-1 Remote I/O with a redundant power supply unit, a redundant
communication interface, and 16 I/O modules (front view)
The mounting termination unit is accommodated in a suitable field housing
(junction box) to protect it from environmental exposure. Field mounting in
hazardous areas requires approved field housings with increased safety
3BDD010422R0101
Communication Interface for PROFIBUS DP, CI920
I/O System S900

2. Introduction

9