No.27 (1999)

Yokogawa periodically publishes the Yokogawa Technical Report, which contains articles that take a detailed look at the technologies employed in Yokogawa's products. At this site you will find links to all of the reports that have been published since 1997 as well as links to PDF files containing the full text of selected articles from each issue.



  • MORIOKA Yoshitsugu*1

*1 Fieldbus Center

Field communication function is one of the elements of an enterprise information system. The information generated in field devices has been used mainly for control and maintenance management. Yokogawa currently provides hybrid field communication devices based on the BRAIN protocol for these purposes. This article describes our design concept for full-digital field communication products based on the FOUNDATION™ Fieldbus.


  • HASEGAWA Yoshio*1
  • TERANISHI Yoshikazu*1

*1 Electronic Devices Design Center

This paper introduces the recently developed fieldbus MAU (medium attachment unit) IC, which includes a power supply block, a transmitter block and a receiver block. The power supply block generates two regulated voltages from the powered bus. The transmitter block controls the rise and fall time of the bus signal so as to meet the fieldbus output timing requirements and outputs that signal to the bus. The receiver block includes a filter and comparators. In addition, the IC includes a low-power signaling function and a jabber inhibit function. A supply current of as small as 0.7 mA is achieved so that the IC can be used with field devices. The IC uses Yokogawa's 3- mm bipolar process and is housed in a 44-pin plastic quad flat package (QFP). This paper outlines the circuit configuration of the IC and the results of its evaluation.


  • KOYAMA Etsutaro*1
  • NIKKUNI Masaaki*1
  • ODOHIRA Tetsu*1

*1 Industrial Measurement & Control Business Division

For a long time now, we have appreciated the standard 4-20 mA signal for 1- to-1 analog communication lines in various plants. The time has now come for a new type of communication, namely, fieldbus, which features digital transmission on 1-to-1 communication lines. We have just developed an EJA series differential pressure transmitter with FOUNDATION™ fieldbus communication to be used as one of the main sensors in a plant. The fieldbus communication is to be supported by all models of the EJA series. That is, all new EJA models are equipped with the Standard Resource Block and the Standard Analog Input Block.

This paper describes the structure and the characteristics of the EJA transmitter with fieldbus communication.


  • SEKIGUCHI Toshio*1
  • TAKAHASHI Seiichirou*1
  • MIYATA Toshiyuki*1
  • KUROMORI Kenichi*1

*1 Industrial Measurement & Control Business Division

A new model that is compatible with FOUNDATION™ Fieldbus has been developed as an enhanced product of the YEWFLO* Vortex Flowmeter series. A single YEWFLO unit can measure fluid flow, gas flow and steam flow over a wide range of temperature and pressure. YEWFLO flowmeters cater for pipelines with a nominal diameter of 15 to 300 mm. The product lineup has been extended to include flowmeters that provide fieldbus-based output for bidirectional high-speed digital communication, as well as the conventional BRAIN-based 4-20 mA analog output and pulse output. This paper describes the characteristics of the new YEWFLO*E compatible with the fieldbus communication protocol.


  • IMORI Hiroshi*1
  • MIZUSHIMA Fuyuki*1
  • TTOMITA Shoji*1
  • HAYASHI Shunsuke*1

*1 Industrial Automation Systems Business Div.

We have developed fieldbus communication functions for our distributed control system CENTUM CS that comply with the specifications of the Fieldbus Foundation. These new functions enable cascade control of the CENTUM CS control function and the field device control function, and also support the operation and monitoring functions of the field device control function. The fieldbus communication module (ACF11) interfaces with the fieldbus. It can also be connected to a node on the remote IO bus (RIO bus), thereby making the system construction flexible.

This paper introduces the characteristics of the CENTUM CS fieldbus system, with the main focus on its communication functions.


  • KURIYAMA Kan-e*1
  • MATSUMOTO Noriko*1
  • KASE Syuji*1

*1 Industrial Automation Systems Business Division

This paper describes one of our most recent developments, the CENTUM CS Fieldbus Device Management Tool software. This software runs on a personal computer in the instrument room. It accesses field devices via the FOUNDATION™ fieldbus, in order to display status information and messages and enable parameters to be displayed and set. Remote access to field devices from the instrument room can greatly simplify their maintenance.


  • TAKEISHI Masashi*1
  • OGATA Yoshikazu*1
  • TSURUNOSONO Ryuuichi*1
  • KIYONO Shinjirou*1

*1 Environmental & Analytical Product Business Division

The development of the MLSS analyzer was an important breakthrough in process analyzers for the sewage field. The latest model, the SS400 MLSS analyzer, provides highly reliable measurement over concentrations ranging from 0-500 mg/l to 0-20000 mg/l. The measurement of low concentrations was made possible by adopting a measurement method that compares transmitted light with scattered light. The effect of disturbance light was eliminated from the measurement by devising an optical system that uses pulse-driven light emission. During this development, we also reviewed the maintainability of the liquid analyzer and introduced measures such as a self-cleaning floating holder and simplified calibration to facilitate maintenance management. This paper reports on the characteristics and technical background of the SS400 MLSS analyzer.