PCC-IV Instruction Manual (rev. 0.1)
Page 1-3
Section 1 - Product Overview
Distributed Control System Concepts
The PCC-IV represents the fourth generation of process controllers from Preferred Instruments. This controller is
designed to provide a true distributed approach to control applications. The PCC-IV provides automation features
that are self-sufficient and will operate independently from the remainder of the control system. The PCC-IV can be
configured as a data collection I/O module (DCS-IV) for a data acquisition system, as a multi-loop controller, or as
a traditional single loop controller. In all cases the PCC-IV will communicate on a n
etwork with a central operator’s
station using the industry standard Modbus protocol.
Because the PCC-IV is self-sufficient
, control will be maintained even if for any reason, the operator’s station(s) or
network are completely disabled. Un-like a PLC, a single PCC-IV or DCS-IV failure affects a relatively small
percentage of the overall system’s I/O. Considering all the above, the need for redundant power supplies,
microprocessor cards, or I/O cards is greatly reduced.
The backbone of the system is the network. The network used between controllers is based upon the industry-
standard Modbus protocol,
using the controller’s integral RS-485 and Ethernet communications ability. This network
communication is optically isolated.
Analog and Discrete Control Functions
The PCC-IV includes all the control functions needed for your application. The controller includes not only traditional
analog functions but also many discrete (logical) and timing functions. The controller can handle many tasks that
would normally require the use of a PLC, and the use of option cards permits expansion of those discrete I/O
capabilities (up to 13 DI and 10 RO/DO). Discrete functions can also be readily integrated with analog functions
which has been traditionally difficult to accomplish with a PLC, due to its purely logical basis. The combination of
integral analog, discrete, and timing functions renders the PCC-IV a very powerful control solution.
Configuration Concepts
In many applications, the PCC-IV is shipped with a standard factory configuration, but it is designed to permit easy
modification or development of control strategies in the field. The PCC-IV can modify parameters using front panel
touchscreen display. Any Windows computer can configure the logic graphically with the PC4_Draw software. The
PCC-IV USB port allows PC4_Draw to monitor live data, change any parameter, and read/write entire function block
configurations and provides full documentation capabilities.
Com-Link Data Highway Concepts
The PCC-IV can be networked together over an industry standard Modbus network (RS485, or Ethernet Modbus
TCP/IP). Modbus is an open architecture format to allow flexibility for future system expansion and/or modification.
The RS485 and Ethernet networks are electrically isolated controller-controller, and controllers-SCADA. The RS485
network allows controllers to be located up to 4000 feet apart, and up to 31 controllers (plus the Master) can be
networked
.
The use of Modbus as a communications protocol allows the PCC-IV
to be integrated with other’s
equipment and on networks supplied by ourselves or others.
