Fieldbus Profibus

Industry standard protocols (OPC, Fieldbus, Profibus, Hart, etc.)... 

Communications Open systems Fieldbus/Profibus etc Limited, specialized Difficult with bus networks... 

The mass flow rate is calculated directly by multiplying the time difference or the phase shift with the calibration constant of the flowmeter thermal effects on the mass flow and density reading have to be included as well. This is commonly done with a microprocessor. The primary output from a CMF is mass flow. However, most electronic designs are also capable of providing temperature, density, and volumetric flow data. Further, totalizers provide mass or volume totals. Analog (4 to 20 mA) and digital output protocols are supported (e.g., PROFIBUS, FOUNDATION Fieldbus, HART, Modbus, scaled pulse, and others). 

During international fieldbus standardization at the start of the 1990s a physical layer had been specified as IEC 61158-2 with an option for intrinsic safety. In the meantime, two standardized fieldbus systems comply with said standard Profibus PA and Foundation Fieldbus HI. These are the most important characteristics ... 

Meanwhile, an increasing number of transmitters and positioners etc. is available either with a Profibus PA or a Foundation Fieldbus HI interface (or with both of them). 

These results can be generalized, of course. In practice, today they are applicable to Profibus PA and Foundation Fieldbus til only, because the apparatus... 

The high-performance, all-digital, multidrop communication protocol for use in the process-control industry is known as fieldbus. Presently there are several regional and industry-based fieldbus standards including the French standard, FIP (NFC 4660x approved by UTE), the German standard, Profibus (DIN 19245 approved by DKE), and proprietary standards by DCS vendors. As of 1997, none of these fieldbus standards have been adopted by international standards organizations. 

PROFIBUS family is another proven and popular fieldbus system in use in industrial automation system. The PROFIBUS system has three compatible versions that operate all together seamlessly. 

Stmctural details of PROFIBUS have been presented in Fig. IX/2.2.1-1 [2]. Like foundation fieldbus, here also there are different bus systems, viz. FMS, DP, and PA. 

High and low limit checks for transmitters have been in practice for quite some time, even when discrete instmmentations were in use. Now with the DCS it is very easy to monitor out of limits for the transmitter and open-circuit and short-circuit tests for sensors like resistance temperature detectors and thermocouples. Most of the transmitters are monitored for out of span (e.g., <4 or >20 mA). Also since smart transmitters have a diagnostic system, they also can detect faults and isolate them, that is, the output of a faulty transmitter could be inhibited generating an alarm. The transmitter is connected via HART/Profibus/fieldbus, and such detections are more explicit and well reported in the system. Also there exists a facility for the operator to select any transmitter manually. 

Two well-known fieldbus systems are Profibus and AS-I (Actuator Sensor... 

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