Most people think of fieldbus as digital integration of field devices with process automation systems and that working with fieldbus can only be accomplished with fixed assets (such as PCs) located in fixed locations, but there are also a number of portable tools available that can make specific fieldbus tasks a lot easier and help users get a better return on their fieldbus investment. There are very good reasons for using portable tools, and a wide range of products are available with different functions and price levels.
So why use portable tools? One of the big advantages of Foundation fieldbus is the ability to access information about a device remotely from the control room, instrument shop or anywhere the information is needed. The ability to do diagnostics remotely can save a lot on maintenance costs and avoided failures.
Today's workforce is increasingly mobile, so the future of device diagnostics may not be limited to the confines of a control room. Today's portable tools can provide the same functionality as a process workstation, or they may be simpler or less expensive tools designed to test specific functions. For example, a user may want to evaluate existing wiring to see if it meets fieldbus physical layer specifications, or diagnose potential physical layer issues such as segment noise or communication jitter. Maybe someone needs to go out to the field for a visual inspection. Whatever the needs, portable tools can help realize flawless fieldbus project execution and keep segments and devices running to their optimum potential.
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The Value of Preconfiguration
If you are planning or are in the midst of a fieldbus project, you may want to consider pre-configuration prior to commissioning. In the installation phase, you can use portable tools to pre-commission and tag Foundation fieldbus devices. Successful device downloads require all of the information in the device, such as tag name and node address, to be identical to the information stored in the host system configuration. Preconfiguring devices before control system commissioning activities begin ensures consistency and can speed time to start-up.
The Importance of the Physical Layer
Engineers with experience in fieldbus projects say that most of the mistakes made during fieldbus installation are related to the physical layer. Since Foundation fieldbus is a digital network, it has physical layer requirements that are somewhat different from those for analog installations. Portable tools are now available that can check physical layer issues such as the suitability of existing wiring, segment noise, low voltage or communications jitter.
In the instrument shop, portable tools can offer a degree of convenience and familiarity to instrument technicians. Portable tools can be used to perform a quick check of a new device out of the box before taking it to the field for installation. Some can also be used to set up and pre-commission devices before taking them to the field for installation.
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Portable tools, such as the Emerson 475 from Emerson Process Management, typically have simple, easy-to-use interfaces that are designed specifically for use by maintenance technicians doing a series of fieldbus-related tasks. While today's sophisticated asset management applications and process automation systems offer a lot of functionality, maintenance technicians may not want to take a course in how to use a DCS in order to accomplish what can be done via a tool they're already familiar with.
Work in hazardous areas requires equipment that can be used in Class 1 Div 1 areas. This requirement for being hardened and approved for hazardous areas is probably one reason why tablets and smartphones have not really taken off as everyday tools in places such as refineries and chemical plants. Although you will still pay a premium, you can get some highly functional wireless workstations that are essentially environmentally hardened tablet PCs.
Classes of Portable Tools
Portable tools fall into three general classes: Laptops and wireless workstations, handheld tools, and remote wireless clients. Each of these has its own advantages. Many users have a combination of these tools, so it's not a case of one tool versus another.
Laptops and USB Interfaces. If you want the functionality of a workstation in a familiar package, a ruggedized laptop or notebook PC is a good choice. There is a wide range of laptops designed specifically for manufacturing applications. Of course, a laptop offers a more full-featured user interface than a handheld. Because it is a PC, laptops can offer easier integration with plant asset management systems and other applications.
Most suppliers now offer USB fieldbus interfaces that can be used in conjunction with a laptop or notebook to allow direct access to Foundation fieldbus H1 segments and field devices. This allows users to commission, configure and troubleshoot the devices both on the bench and in the field. USB fieldbus interfaces are available from Emerson Process Management, Softing and National Instruments. The newly released Emerson USB fieldbus interface provides power to the fieldbus segment, which can be useful in start-up situations or emergencies where power is not available.