1 March 2002
Internet technologies web plant floor
By Mark Janke
TCP/IP on Ethernet and on a wireless link run these devices.
Internet technologies, such as TCP/IP on Ethernet, are growing in popularity as methods of communicating with field instrumentation. A benefit of this trend is that several commercial technologies using TCP/IP on Ethernet can provide advanced management features within instruments.
Technologies such as the Web provide easy access to devices from Web browser software that is included in most operating systems.
This access provides a simple management mechanism to alter calibration settings, review user documentation, and update maintenance logs within a device.
This management mechanism significantly reduces maintenance costs and increases ease of use. Within some installations, TCP/IP on a wireless link can replace Ethernet to further increase the benefits.
A SPICY VARIETY AVAILABLE
With the proliferation of the world's most common communication technology (TCP/ IP on Ethernet) on the factory floor, manufacturers may begin to provide communication services that extend past simple data acquisition.
One such service that can significantly improve instrument usability is remote management. A variety of technologies supported by TCP/IP on Ethernet are available to support remote instrument management. These include, but are certainly not limited to, simple network management protocol (SNMP) and the World Wide Web.
If these technologies do not meet the instrument vendor's requirements, the vendor may choose to develop a custom solution that works over TCP/IP and Ethernet. However, the effort to develop a custom answer is far greater than a Web-based solution.
Let's discuss the functionality that remote instrument management provides and the available technologies to leverage when developing a solution.
Some of the most obvious and compelling benefits of remotely managing field instrumentation are remote configuration and monitoring. Troubleshooting that traditionally takes place locally by plugging into an instrument or viewing its local display can now happen from a remote location.
How remote is simply a function of how the instrument connects to the outside world. If the instrument connects to a facility LAN, any computer on this network (with the appropriate remote management application software) can access and remotely manage the device.
If the facility LAN links to the Internet, perhaps through a firewall that allows management communications, remote access may be from anywhere on the Internet.
Remote configuration may include the ability to manipulate instrument calibration (e.g., zero, span, hysteresis), alarm points, shutdown sequences, and maintenance sequences (e.g., on field analyzers).
Remote monitoring may include the ability to watch run-time values, alarm values, and sequence-of-event records.
The ability to remotely access instrumentation can significantly increase facility uptime, as the response to many instrument problems is almost immediate, and no travel to the physical location of the instrument is required.
Remote management technologies also reduce maintenance costs because they access more instruments in less time.
SIMPLE NETWORK SECURITY PALES
SNMP started as a tool to manage data communications equipment. During the past few years, it has provided remote management of that technology. Recently, SNMP has made some headway on the factory floor.
The greatest advantages to using SNMP are as follows:
- Widely available documentation
- Available development expertise
The largest disadvantages of SNMP are the following:
- Implementation is far more difficult and time consuming than for competitive technologies, mainly due to the complexity of SNMP.
- Management software applications must be aware of the available information within managed devices. If this information changes, the management software application must also change.
- Security support is very limited. The latest versions of the SNMP standard have improved security features, but SNMP security still pales in comparison with competitive technologies.
BROWSING THE PROCESS . . . HMM
Originally designed for browsing documentation over the Internet, the Web now supports all requirements for instrument management. Web servers originally designed to simply expose documents are now extensible to support manipulation of the system on which they run.
These days, Web servers are so small they embed into field instruments. Web pages within instrument Web sites can display information pertaining to that instrument. Web content such as graphics, sound, and animation display monitored information such as instrument alarms.
Instrument Web sites also expose Web forms, originally designed as a medium for users to submit information to a Web site, to controls such as radio buttons and drop-down list boxes.
Manipulation of these controls and submission of a form provide a means for instrument configuration changes.
The advantages of using the Web for instrument management are user familarity with the Web and management from computers, personal digital assistants (PDAs), and other devices that support Web browsers.
The main disadvantage is that Web browsers surf only one instrument at a time, at least within one instance of the browser or browser window.
Some competitive technologies support management of many instruments at once.
HACKERS ACCESS THE INSTRUMENT
One of the first questions that comes up when discussing using the Web for instrument management is security. How secure are instruments and their configurations? Can hackers access the Web site within an instrument and wreak havoc within a facility?
The answer to these questions is yes. Just as hackers can access secure Web sites such as those used by online auction houses and banking institutions, hackers can access field instruments.
Fortunately, the same technologies that ably protect commercial Web sites can also safeguard field instruments.
The risk of security breaches is further mitigated because while a hacker exerts the same effort to hack into an instrument as into a commercial site, the payback is far less. Finally, note that access to LANs and the Internet is not limited to computers with a physical Ethernet connection. Wireless technology supporting TCP/IP can provide a connection between managing hardware and managed instruments.
This means that field instruments respond to input from anywhere Internet connectivity is available. PDAs and other handheld devices with wireless and Web browsing capability can manage instrumentation.
Considering the payback and the relatively low level of effort required to add remote management capabilities to field instrumentation, we expect to see an increase in management capabilities in current and next-generation instrumentation. IT
Behind the byline
Mark Janke is a professional engineer and ISA member. He works as a field application engineer for Intrinsyc Software in Vancouver. This is an edited version of his paper presented at ISA 2001 in Houston.