Differential pressure transmitters, which serve as the core of field instrumentation, are widely used to measure the flow rate, pressure and density of liquids, gases and steam, as well as the level of liquid in a tank.
There is strong demand from industrial plants for more accurate plant operation and labor savings in both plant operation and management as a means of improving yields. Not only are field devices required to be more precise and stable, but they must also be more intelligent in order to cut the cost of labor for plant operation and maintenance. In 1988, Yokogawa Electric released their first pressure transmitter with the BRAIN communication function-a communication protocol in which the 4-20 mA analog signal is mixed with digital signals. Since then, they have continued to release newer models of these pressure transmitters as well as striving to produce increasingly intelligent pressure transmitters, such as the DPharp series.
Recently, the focus has turned to the standard fieldbus (with its multidrop connection and full digital transfer) that will replace the conventional BRAIN communication with 1-to-1 connection. This paper introduces the EJA series pressure transmitter that supports the fieldbus protocol advocated by the Fieldbus Foundation. Figure 1 is an external view of the transmitter.
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