• ISA50, Signal Compatibility of Electrical Instruments


    Scope

    1. To develop standards for signals used in process measurement and control, to transmit information between subsystems or separated elements of systems. Such signals may be analog or digital. However, data highway and other time-shared transmission paths, such as those within the scope of ISA72, are excluded.

    2. To continue to serve as the U.S. Technical Advisory Group for IEC-SC65A/WG4: Interface Characteristics.

    Purpose

    To define a common interface between components of electronic measurements and/or control systems.

    A Word from the Chairman

    Richard Caro, Chairman of ISA50 since 1993, and Cullen Langford, Chairman from 1987 to 1993, wish to thank everyone who participated in the development of the ISA-50.02 Fieldbus standards. The standards were administratively withdrawn as ANSI standards and have now also been withdrawn as ISA standards as they are no longer in use due to the issuance and acceptance of a more current IEC 61158 standards series.

    The technical report ISA-TR50.02, Parts 3 & 4-2000, Fieldbus Standard for Use in Industrial Control Systems, Parts 3 & 4: Technical Report for Fieldbus Data Link Layer - Tutorial, remains available.

    ANSI/ISA-50.00.01-1975 (R2012), Compatibility of Analog Signals for Electronic Industrial Process Instrumentsis one of the most widely used standards in industrial automation (print and downloadable versions are available), specifying 4-20 mA as the signaling range for analog data transmission of instrumentation and control signals. The standard document is simple, and the technology is very mature. All ANSI standards must be either withdrawn or re-certified every five years. There have been no technical innovations in this area since 1972, and the trend is to move gradually to digital fieldbus transmission, however, the annual volume of instruments sold with an ISA-50.1 conforming analog signal is still much larger than all fieldbus instruments combined.

    There have been some proprietary additions to the 4-20 mA implementations, particularly to use the band below 4 mA but above zero to signal a specific system malfunction, and likewise to use a small band above 20 mA as well. There has been no general call to standardize on these small additions, however.

    Although the ISA50.4 subcommittee had been inactive for several years, ISA-TR50.02, Part 9, Fieldbus Standard for Use in Industrial Control Systems: User Layer Technical Report  (downloadable version available), was published in 2000. The document is a valuable tutorial that captures the knowledge of a unique expert along with the analysis of a complete synthesized digital control system. Former ISA50 Chair Cullen Langford was integral in converting the text, almost 1000 pages, into a workable electronic format. The subcommittee and ISA50 thank him for his remarkable efforts.

    For more information, please contact

    Eliana Brazda
    ISA Standards Administrator
    ebrazda@isa.org
    (919) 990-9228

  • Contacts

    Managing Director
    Don Bartusiak

    don.bartusiak@exxonmobil.com
    (281)384 1632

    Voting Member Chair
    Richard Caro

    rcaro@cmc.us
    (978) 2061449

    Voting Member
    Patricia Brett

    patricia.brett@honeywell.com
    (215) 6413373

    Voting Member
    Richard Canfield


    Voting Member
    Robert Crowder

    r.crowder@comcast.net
    (610) 3450033

    Voting Member
    Em DelaHostria

    em.delahostria@gmail.com
    (440) 6467324

    Voting Member
    Udo Doebrich

    udo.doebrich@khe.siemens.de
    49

    Voting Member
    Bernard Dumortier

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    333632056403

    Voting Member
    Ben Gross

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    (810) 9470609

    Voting Member
    Ashok Gupta

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    (732) 2742648

    Voting Member
    Toshi Hasegawa

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    Voting Member
    James (Jim) Jamison

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    Voting Member
    Robert Ketcham

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    Voting Member
    Klaus-Peter Lindner

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    Voting Member
    Timothy Madden

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    Voting Member
    Francis McKenna

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    Voting Member
    Lewis Natiello

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    Voting Member
    Lee Neitzel

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    (512)963 9909

    Voting Member
    Patrice Noury

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    Voting Member
    Evan Pageler

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    Voting Member
    Tom Phinney

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    Voting Member
    Edward Sederlund

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    Edward Skabowski

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    Herman Storey

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    Nathan Tobol

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    Voting Member
    Clyde Van Haren


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    Voting Member
    Robert Webb

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    Voting Member
    Christopher Williams

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    (315) 9265079

    Voting Member
    Gregory Winchester

    gre_winchester@nema.org
    (703) 8413299

    Voting Member
    Graeme Wood

    gwood@iee.org
    44 441883627797

    Staff Contact
    Eliana Brazda

    ebrazda@isa.org
    (919) 9909228