field networks have been used for more than a decade, which has proven its value in the world of industrial automation applications. In most cases, the field bus network process plant to connect the host computer system and the field devices.

Field devices discussed herein are typically meters, analyzers, and control control valves. The most common type of meter is a temperature, pressure, flow and transmitter level - while a typical process plant may also contain several other types of variable process transmitter.

Common type of measuring component analyzer chemical parameters, such as moisture, carbon dioxide, methane and other gases and liquids. Control valves provide continuous flow control of liquids and gases.

Host computer system connected field devices, including control systems, enterprise resource planning (ERP) and asset management systems. The control system is generally discussed herein or adjust the basic process control system. Another control system is linked fieldbus devices, including advanced process and security systems.

fieldbus field devices connected to a host computer advantage of the high-speed data communication system, comprising:

• Reduced costs due to the configuration and health management of networked devices;

• Electronic documentation of networked devices saves costs;

• Pre-maintenance to increase uptime;

• Pre-maintenance for better performance;

• Pre-maintenance reduces maintenance costs.

of the field instrument to control the 4-20 mA wiring system: In almost all cases, the fieldbus are wired devices, as replaced. This 4-20 mA signal is used to transfer the measured process variables to the process control system.

In contrast, the field bus is provided with a high-speed bidirectional data link between the field devices and the control system can be a vast amount of transmitted information. The most important information is the health data meter, kept in advance in case of need, they can be used to calibrate the host computer arrangement of the system.

Calibration arrangements only need to replace the periodic maintenance of the occasion, can save maintenance costs, since the field devices within their parameters of calibration operation is not necessary. When necessary, calibration can improve performance because the need for frequent calibration device key field, reducing eventual overcoming of drift.

Predictive maintenance is probably the most important benefit brought by the fieldbus system. Using data provided by the fieldbus, the factory can pre-discover problems before they occur. Once the maintenance work can be arranged in advance, instead of waiting for problems then occurring to react, cost reduction and greater safety.

But the main benefit of pre-maintenance is to avoid downtime. To do the whole process of stopping if a field device failure occurs, usually for maintenance and replacement of equipment.

Fieldbus is a generic term for many digital network industries, including, but not limited to, FOUNDATION fieldbus (Foundation Fieldbus), Hart (HART), Ethernet / IP, Modbus TCP and Profibus. Many fieldbus networks, including those mentioned above, are migrating to Ethernet-based protocols for a variety of reasons.

Why Use Ethernet?

Fieldbus benefits for many years a variety of process applications, has been well documented, fieldbus use proprietary protocols are already installed most of this and other Ethernet-based protocols. The Ethernet-based fieldbus offers better performance, lower cost and is simple to install and maintain.

When referring to Ethernet term in the field of business, generally refers to the use of the TCP / IP protocol, the Ethernet network. In industry, the term Ethernet refers specifically to the underlying hardware only, not including the protocol, the protocol can be used according to your preferences by the user. The bad news is that there are many competing industrial Ethernet protocols. The good news is that all protocols can run on the same Ethernet hardware, but also at the same time.

A good price / performance ratio can be an important factor in switching to Ethernet. Just a few years ago, a leading fieldbus organization also pushed for a fact: they use proprietary protocols for fieldbus devices, sold 1 million in 10 years. This value in comparison with other competitors may

impressive, but compared to the number of Ethernet devices installed in the world, insignificant.

As the protocol leading to computer connection, Ethernet participants installed in the world billion, most commercial applications. It has produced a large number of economies of scale, so that Ethernet hardware prices continue to decline, and improve performance. Because Ethernet is the world standard, suppliers, price competition, has a great driving force to promote a better product came to exist.

Fieldbus organizations have adopted commercial Ethernet economies of scale advantages, launched a low-cost high-speed network. High speeds allow for quick updates of monitoring applications. According to the characteristics of process control, high-speed real-time control can be achieved.

Installation and maintenance are very easy due to the extensive use of Ethernet. There are several reasons, first, compared to proprietary networks, it is easy to find staff familiar with Ethernet technology. Second, the hardware and software tools used for installation and diagnostics are very numerous and inexpensive. Finally, it is possible to rely on the personal support and IT factory of the company and maintenance, because IT staff understand Ethernet. After integrating their industrial and office networks, end users need only a few network maintenance, when technology and integrated communication, is to earn more revenue.

Ethernet offers more than fieldbus benefits, many users benefit from different applications. In particular, an Ethernet switch allows the field bus to be attached to the programmable automation controller (PAC) layer.

Direct is the best

When flying from one city to another, non-stop flights are always better than the transfer for a flight. The same thing applies to the field bus connected to a higher order computer system, is connected directly to a fieldbus device or ERP asset management system better than the control system switching through an intermediary.

bypass control system directly connected to a central computer system, such as an ERP system or resource management, using an easier-to-Ethernet Ethernet fieldbus embodiment. This is because most host computer systems use Ethernet for communication.

In a typical process plant, most fieldbus devices are not directly connected to real-time control, but are designed to monitor. Some installations have up to 70% of the field devices that have nothing to do with the control functions. Therefore, each field device must be connected to the control system this hypothesis is not true, nor should they play valuable.

For example, environmental applications such as EPA (EPA) monitoring and reporting needs of a variety of field devices, and which does not need to be connected to the control system. ERP applications such as a storage management device to enter the field, but does not require milliseconds refresh rate, or the control system requires deterministic.

The bypass control system offers many benefits. First, direct connections eliminate intermediate hardware and software systems. Second, the question of field devices is no longer part of the control system, without adding to the general validation and maintenance procedures. Again, access to field devices can be controlled by existing IT security systems.

This non-critical field device information, via Ethernet and an unlimited gateway, delivered directly to the process monitoring applications. Not only the main message to the whole set the engineering unit, and device status can be triggered by events or way to send cycle, continue to be monitored and communications.

Working in remote service tools and network layer application asset management, you can also configure and manage connected devices. Standard IT security and data management tools can be used for access control.

Ethernet Fieldbus facilitates the application of the PAC

In the early days of use, most fieldbus control systems were variants of DCS. Ethernet now provides a common communication protocol, and fieldbus is an option for PAC control systems. This can reduce the cost of the process control system because the PAC is generally cheaper than DCS systems.

Ethernet covers leading commercial and manufacturing office manufacturers, combined with the use of PAC and Ethernet / IP Fieldbus devices improve product quality, promote green manufacturing and increased productivity. In one of

manufacturers use a PAC as their main real-time control platform. PAC uses a built-in Ethernet / IP device, so the plant is selected to support this arrangement, as its type of fieldbus Ethernet.

Thus an Ethernet / IP support flow meter to measure and control the mass flow in a continuous associated staining process control plant. The manufacturer will perform a field test comparison and select a mass flow meter with greater accuracy. Connecting the meter directly to the PAC via EtherNet / IP offers multiple benefits. When more value field devices connected via Ethernet type fieldbus control systems, asset management systems and ERP systems, these flow meters can provide

This instrument has the ability to simultaneously measure various parameters, including mass flow, product density, process temperature, volume flow rate, concentration and viscosity. Factory I hope to be able to monitor these parameters, but do not want more than one line, use solution is to use a high-speed 100Mbps Ethernet / IP protocol.

Plant can use the advanced instrument monitoring diagnostic parameters, the influence on the process is determined in advance from the coating, parts combination, corrosion, and by a gas condition. Prediction before problems occur, pre-maintenance early, reducing costs and reducing downtime.

The most obvious benefit of these applications include a 40% reduction in placement time, a 25% reduction of circuit identification, device integration and process time tuning time. As a network node, you can immediately identify a meter, which is another income, along with the transparency of the instrument, from the shop floor to the corporate systems.

There is no doubt that the fieldbus will continue to evolve towards Ethernet. To stay competitive, fieldbus organization would have the advantages of using Ethernet to bring profitability.

The end user will have a field bus of the Ethernet type, simply from the field device, directly connected to the control system or host computer platforms, such as DCS, PAC and ERP asset management systems. With the increase in the number of PAC process plant fieldbus style use Ethernet will be very popular and natural.

More and more plant technicians are becoming familiar with Ethernet and encouraging the use of Ethernet in process plants. The internal IT team will also like the Ethernet fieldbuses as they are similar to the company's computer system network. This floats Ethernet Fieldbus is constantly advancing, vendors and end users are also being applauded.

Not all Ethernet fieldbuses are the same

Fieldbus organizations as advocating their Ethernet is the best, most are connected to Ethernet / IP TCP on commercial basis, and can provide real-time and reliability required for industrial applications. These advertising needs of end users and system integrators to undoubtedly judge Ethernet fieldbus type has a lot of different, and often not compatible.

For example, Ethernet / IP and PROFINET is a fieldbus of the Ethernet type, but not necessarily, mixed and combined, both connected to the gateway and / or a standard converter is not the same. In other words, a field device does not support PROFINET connected directly to the programmable automation controller (PAC) with EtherNet / IP port.

One solution to this problem is only compatible field devices and controllers on the same fieldbus. Unfortunately, this usually does not work, because most process plants have existed for field devices in accordance with different fieldbus standards.

Even in a green plant or process, which normally is not possible to buy only depend on one type of fieldbus devices fieldbus standard Ethernet providers. Some special meter is not often used, analyzer and control valves if necessary using a field bus connected to a control system or host computer system, which may also consider supporting network standards.

To solve this problem, many vendors have developed gateway device, you can put in another protocol for the Ethernet fieldbus protocol later. For example, there is an input port that connects the field device to a Modbus TCP PAC having Ethernet port / IP.

Although gateway solution to the incompatibility problem, it is best to avoid using this method. There are the following reasons. First, the gateway increases the total cost of the fieldbus installation. Second, the gateway adds complexity to the design and maintenance

O. Finally, the gateway requires additional spare parts and storage needs.

Foundation Fieldbus High-speed Ethernet promises to be the industry standard, but not all DCS providers will support it. End users who want an Ethernet fieldbus compatible with all standards have to wait a long time before the best use of compatible components, maximum scalability, use a gateway when needed.

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