Yokogawa Electric Corporation (main office: 9-32, Nakacho 2-chome, Musashino-shi, Tokyo; President: Eiji Mikawa; paid-in capital: 3.2306 billion yen) is pleased to announce its successful development of a distributed control system and differential pressure/pressure transmitter supporting fieldbus. These are the first products on the global market to support the fieldbus international standard specification. These products will be available throughout the world on March 12. They are Yokogawa's first step in broadening its lineup of control systems and equipment supporting the fieldbus standard as the company works to significantly expand its fieldbus business.

Changes in the control environment brought about by fieldbus technology

Distributed control systems (DCS), which were introduced in the 1970s, gained rapid popularity starting in the 1980s because of their high reliability and superior functions and performance. Until now, advances in DCSs and the field devices which provide field information to DCSs have been driven by the proprietary technology of a number of vendors. In recent years, however, this field has felt the impact of the trends toward open standards, downsizing, and lower prices. As a result, control system vendors now need to create systems which are optimized throughout, and which can effectively integrate and utilize the various types of information on a network in addition to providing a simple "open" interface.

Fieldbus technology, which utilizes digital communications based on an international standard specification to link control systems with field devices in the field, is at the core of this trend toward introducing open standards for control sites. The standard analog communication system which is currently popular operates at 4 to 20 milliamps. The use of a digital communication system based on an international standard specification instead of this analog communication system will help revolutionize the control system environment. Benefits will include enormous increases in the amount of data transmitted, significant reductions in wiring costs, the establishment of a multiple vendor environment and downsizing in the control field.

Major benefits provided by introducing fieldbus technology

-	Fieldbus technology allows field devices to communicate with each other, enabling autonomous distributed control by field devices.
-	Fieldbus technology makes it possible to transmit data with a higher level of precision than that provided by analog communication. In addition, digital communication makes multiplexing possible. As a result, field devices can transmit a wide variety of information in addition to indicator values and control outputs.
-	Fieldbus technology ensures interoperability, allowing for the field devices of multiple vendors to be used in combination--something that was not possible in the past.
-	In the past, control systems and field devices were linked in one-to-one connections. With fieldbus technology, however, multi-drop connections (in which a single cable is used to connect multiple field devices serially) can be used. This will help reduce wiring costs significantly.
-	Fieldbus technology allows some field device adjustments and checks to be performed from a control room.
-	Field device self-diagnostics information can include status information instead of just "normal" or "abnormal" indications. This makes it possible to perform trend analysis in time sequence in order to diagnose failures.

With benefits such as these, fieldbus technology will significantly change the shape of future control systems. It is a promising technology which should revolutionize production sites.

Yokogawa's fieldbus-compatible product lineup

The fieldbus-compatible products Yokogawa is now launching are the CENTUM CS integrated production control system and the DPharp EJA differential pressure/pressure transmitter. Both of these products are the number-one products in their class in Japan, and have major shares of the international market as well. By expanding its lineup of fieldbus-compatible equipment through these products, Yokogawa is helping to evolve the actual fieldbus technology used at plants while providing a high level of reliability. All of the companies in this field are working hard now to develop fieldbus-compatible products, and some products have been introduced as field test products. However, Yokogawa is the first company to introduce a fieldbus-compatible DCS which is an actual completed product. In addition, Yokogawa is the first to globally launch a fieldbus-compatible sensor. In the future, Yokogawa plans to continue this trend by expanding its fieldbus-compatible lineup to include the CENTUM CS 1000 production control system and YEWFLO vortex flowmeter, as well as electromagnetic flowmeters, temperature transmitters, product analyzers, etc.

CENTUM CS integrated production control system

Yokogawa holds the top share in the Japanese DCS market. The CENTUM CS is Yokogawa's flagship system in this field, intended primarily for large plants. This product has received much praise for its high reliability and performance, superior engineering environment, and other features.
The CENTUM CS comprises the following: an Information and Command Station (ICS) which is used by the operator to operate and monitor the system in a control room; an engineering workstation (EWS) which is used for engineering; a field control station (FCS) which executes controls in the field; and system software. Fieldbus-compatible CENTUM CS models also have a PC for managing field devices at a site and engineering the fieldbus communication environment, and an extra fieldbus communication module in the FCS. Fieldbus-compatible models also have extra software, consisting of equipment management tools and engineering tools used on the PC, and dynamic data exchange (DDE) software which is used to transmit to the the PC field device data collected by the ICS.
The fieldbus-compatible CENTUM CS can of course be introduced in new systems. In addition, fieldbus-compatible features can be added to previously installed CENTUM CS units to support fieldbus technology while allowing the customer to continue using an existing system. The environment provided by the CENTUM CS was described above.

Main applications
Production line control in all types of process automation fields, including petroleum, petrochemistry, chemistry, steel, paper pulp, food and beverage products, chemicals, ceramics, clean-water and wastewater systems, electric power and gas.

DPharp EJA differential pressure/pressure transmitter

In developing the DPharp EJA, Yokogawa was the first company to use a silicon resonant sensor to achieve a high precision level ((0.1%) while providing long-term stability as well as reduced size and weight. This differential pressure/pressure transmitter has been highly praised by a variety of industries in Japan and abroad. It is a truly international product, with more than half of product shipments going to overseas customers.
The fieldbus-compatible DPharp EJA model has a newly developed amplifier unit which converts measurements to signals before outputting them. Customers who are already using the DPharp EJA can also upgrade their current units to make them compatible with fieldbus technology. The environment provided by the DPharp EJA was described above. Because it can be used to measure both differential pressure and pressure, the DPharp EJA makes effective use of fieldbus technology by allowing two different types of information (differential pressure and process pressure) to be transmitted on a single bus. Differential pressure/pressure transmitters are the most commonly used type of field device. For this reason, launching the fieldbus-compatible DPharp EJA together with the DCS should accelerate customers' adoption of this technology, especially in monitor systems.

Main applications
Plant piping flow-metering and tank level measurements in all types of process automation fields, including petroleum, petrochemistry, chemistry, steel, paper pulp, food and beverage products, chemicals, ceramics, clean-water and wastewater systems, electric power and gas.

Fieldbus standardization trends and Yokogawa's standardization efforts

Proposals presented through the IEC for standardizing digital communication for field devices go back to 1984. Since 1990 actual standardization has been carried out by the IEC and the ISA SP50 chair. Since that time, the development of a concrete specification was at one time carried out in parallel by the ISP camp and the World FIP camp due to the fact that vendors had split into two groups regarding the matter. In 1994, however, these camps were unified with the establishment of the Fieldbus Foundation. Under the system which is currently established, the IEC and the ISA SP50 chair are working on standardization, while the Fieldbus Foundation works to develop and popularize an internationally standardized implementation specification. The specification was finalized in 1996, and currently companies in the field are developing and conducting field tests with products that are compatible with the specification.

As a core member of the ISP Association, Yokogawa has been involved since an early stage with these standardization efforts. Since the establishment of the Fieldbus Foundation, Yokogawa has participated in its activities and continues to be active as a major member. Yokogawa has played a central role in these efforts. Last year, for example, it provided various field devices and a CENTUM CS system for the Fieldbus Foundation's first field tests done in a multiple vendor environment at Chubu Electric Power.

With the launch of the CENTUM CS and DPharp EJA fieldbus-compatible models, Yokogawa is taking a step which will significantly enhance its fieldbus business. Last year, Yokogawa announced the introduction of Enterprise Technology Solutions (ETS), declaring that it would evolve into a solution provider which would help customers increase efficiency, conserve energy, reduce costs and achieve other goals by creating systems which effectively link processes from the top management level to the production site level.Fieldbus technology is likely to become a core technology used by Yokogawa to implement ETS through the use of open standards and digital technology. Yokogawa, which has established its position in the market as a leader in DCS, will continue to make significant contributions to industry by providing an optimal environment. Yokogawa will achieve this goal by quickly supporting fieldbus technology, which will revolutionize the measurement industry, and by broadening its lineup of fieldbus-compatible products.