The process control industry has grown in leaps and bounds. Product quality improvement is facilitated by the knowledge in realtime of production process parameters. This knowledge gives engineers and operators the information to control this technology in depth which has led to the constant monitoring and control of processes throughout a plant.
There is any number of process control manufacturers in the market. Many of them have developed their own protocols for communication between machines, controllers and computers. Often of these protocols are based on, or developed from serial protocols, be it the RS232 or RS485 standard, (eg Modbus, Profibus, S6/7 etc). These standards have some limitations as to practical cable distance and the amount of cabling that may be needed to centralise a control system. Often process control cabling systems have to exist in parallel with Ethernet cabling used by the plant local area network with obvious cost implications.
Ethernet networks offer many advantages over a dedicated process control cabling system. Shared file resources,e-mail, Internet access, security and file safety, are all components of a properly managed computer system in any industry. Unfortunately, this system lacked the information it needed to give an accurate view of happenings on the production line on the plant floor. The reason for this is that the Ethernet TCP/IP protocol used on most computer and office networks is incompatible with most process control protocols.
Some manufacturers have now started adding Ethernet capability to their systems by adding TCP/IP to process controllers and monitoring applications. Adding this capability has enabled the Process Engineer to move monitoring and controlling applications, from the factory floor, to the office PC. Adding complete monitoring and control of an industrial process to an industrial computer network system allows critical information to flow smoothly between the plant floor and plant management. A fully integrated information system also allows an easy mechanism to look back over time at production trends to make decisions for the future based on past performances of a process.
Unfortunately, there are many process controllers today that do not have the capability to communicate via TCP/IP and the costs of upgrading this equipment is prohibitive.
A solution
SAN People has brought an innovative solution to this problem by its development of the Etherpad range of thin servers. Etherpad enables the connection of any RS232 serial device, such as a process controller, with an Ethernet network. The Etherpad is programmed with an IP address, Subnet Mask and Gateway Address compatible with the Ethernet network it is planned to use the device on. When the Etherpad is running, it becomes 'transparent' passing data to and from the serial device to the application. The Etherpad also contains a web server. Therefore, the Etherpad can be remotely fully configured using any commercial web browser. Parameters such as serial port configuration, Ethernet interface and DNS configuration can be easily changed from anywhere in the world.
Its makers say that as a data logger, Etherpad is hard to beat. The device comes with optional 4,8 or 16 MB flash RAM. It connects to the serial port of the serial device to be logged and into the plant LAN. Data from the logger is saved to memory and can be date and time stamped for convenience. The Logger can be accessed from anywhere on the LAN or WAN and data downloaded via FTP file transfer. The data file is packaged in such a way as to be easily imported into any spreadsheet application, such as Microsoft Excel. The logger is also capable of e-mailing the logged data to a pre-programmed Internet e-mail address.
The amount of data saved is selectable by size or time and the Logger is capable of initiating a connection to a remote host or application when the criteria are met or it will wait passively for an application to connect to it to download the logged device data.
Iscor, until recently, were using an obsolescent Burroughs system to communicate with their more modern Hitachi process control computers in the plant, using a synchronous serial data interface. When the time came to replace the Burroughs with modern equipment communicating over the network using TCP/IP, the company was faced with the problem of how to connect the synchronous serial interfaces of the process controllers to this network. The problem was virtually solved when Iscor control engineers were made aware of the SAN People TCP/IP PAD, which will interface any asynchronous serial device with a TCP/IP Ethernet network. Iscor built up its own hardware to convert the synchronous serial data to asynchronous data which was then input directly to a TCP/IP Ethermod OEM module. In effect a Telnet-style TCP connection was established to the SAN People Ethermod module that can then communicate directly over the network with the process computer.
Another process control solutions provider uses SAN People Etherpads to successfully connect, monitor and reprogram Modicon Modbus process controllers via Ethernet, with no modification needed to any of the hardware or software involved. Upgrades to client sites can now be done from the office with the resultant savings in time and money.
SAN People believes that its Etherpad has proven itself as a cost-effective solution to the process industry - bringing Ethernet connectivity to a host of applications, simply and reliably.
© Technews Publishing (Pty) Ltd | All Rights Reserved
printer friendly version