rotork Pakscan IIS, Техническое руководство

Страница: 15 / 84

Pakscan IIS Technical Manual Issue 1.0
Publication S130E 15
4. OVERVIEW of PAKSCAN
The Pakscan system is a data monitoring and control system which comprises a master station, in this case a
Pakscan IIS, servicing a current loop which can have up to 32 field units connected to it. The current loop
may be up to 20 kilometres long. Figure 5 shows an outline of the system.
In addition to controlling the loop, the master station also provides the external interface to the system. It
supports 2 serial ports for communications to host computers, as well as providing a local user interface.
Alternatively, one of the serial ports may be used to drive a printer to log alarms.
The loop cable is a single twisted pair, with screen is recommended, that forms a complete loop visiting each
field unit in turn and starting and finishing at the master station. This cable carries the 20 mA signal and is
designed to withstand any single fault, open circuit or ground, and still maintain communications with all the
field units.
4.1 Field Control Units
A range of field control units ('FCUs') is available to cater for specific application areas. These may be
summarised as follows:
Integral type field control units mounted within a Rotork actuator electrical housing.
Externally mounted field control unit. Various packages are available, including 'Pakbox', weather
proof box, or rack-mounting. The unit may be used for either actuator control applications, or for
general purpose applications such as pumps, blenders etc. Its complement of I/O is 8 digital inputs, 4
changeover relay outputs, 2 analogue inputs and 1 analogue output.
4.2 Control and Indication
The field units each report information to the master station which can be viewed on the integral LCD display,
or collected from the serial communication port of the master station for use on another display system. The
reported data is already organised and requires no configuration by the user, each field unit automatically
reports all its available data.
Commands to operate the output devices may be sent over the system, the initiation of the command can either
be from the integral keypad (under the correct access code) or from the serial data link. Once again the
organisation of these commands is already configured and the user only has to address the correct register to
implement the command.