SIST EN 62541-8:2015
(Main)OPC Unified Architecture - Part 8: Data Access (IEC 62541-8:2015)
OPC Unified Architecture - Part 8: Data Access (IEC 62541-8:2015)
This part of IEC 62451 is part of the overall OPC Unified Architecture (OPC UA) standard
series and defines the information model associated with Data Access (DA). It particularly
includes additional VariableTypes and complementary descriptions of the NodeClasses and
Attributes needed for Data Access, additional Properties, and other information and
behaviour.
The complete address space model, including all NodeClasses and Attributes is specified in
IEC 62541-3. The services to detect and access data are specified in IEC 62541-4.
OPC Unified Architecture - Teil 8: Zugriff auf Automatisierungsdaten (IEC 62541-8:2015)
Die vorliegende Norm ist eine Anleitung zur Erstellung der technischen Spezifikation für die Beschaffung von Ausrüstungen für den Einsatz in Anlagen zur Erzeugung von elektrischer Energie (Kraftwerke). Dieser Leitfaden ist nicht anwendbar auf Ausrüstung zur Verwendung im Nuklearbereich von Kernkraftwerken. Bei der Erstellung des Leitfadens wurden keine weiteren Möglichkeiten zur Anwendung der beschriebenen Ausrüstung in Betracht gezogen.
Dieser Leitfaden für Kabelsysteme befasst sich mit einem umfassenden Bereich von Maßnahmen und kann für einige oder alle dieser Maßnahmen durch Auswahl der betreffenden Teile angewendet werden, z. B.:
– Vorsehen der Halterungen für Kabel;
– Verlegung der Kabel;
– Fertigstellung der Kabelenden.
Dieser Leitfaden befasst sich nur mit der Installation von Starkstromkabeln für Spannungen bis 20,8/36 (42) kV und der Lieferung und Installation von Kabeln für die Leittechnik. Die Lieferung von Starkstromkabeln wird in EN 45510 2 8 behandelt.
Dieser Leitfaden umfasst auch die Installation des Schutzleiterkabels für die Erdung und den Potential¬aus-gleich bis zur (zu den) Haupterdungsschiene(n), jedoch nicht bis zu unterirdischen Erdungssystemen.
Dieser Leitfaden bezieht sich vorzugsweise auf die Funktion der behandelten Ausrüstung und nicht auf die Art ihrer Konstruktion. Aus diesem Grunde wird die Anleitung zur Spezifikation unter Leistungsaspekten gegeben anstelle von detaillierter Beschreibung der zu liefernden Ausrüstung.
Potentielle Käufer erfahren aus dem Leitfaden, wie die Spezifikation formuliert werden sollte, damit:
– die Ausrüstung von Typ und Leistung her den anderen Teilen der Systeme genau angepasst ist;
– die vorgesehene Leistung erreicht wird;
– die Zusatzausrüstung entsprechend dimensioniert ist;
– Zuverlässigkeit, Verfügbarkeit und Sicherheitsanforderungen erreicht werden;
– die anzuwendenden Bewertungsverfahren und Qualitätssicherungsmaßnahmen ordnungsgemäß berücksichtigt werden.
Der Leitfaden bestimmt nicht die Art der Spezifikation (z. B. detaillierte, auslegungstechnische, funktionelle Spezifikation) oder den Lieferumfang für einen bestimmten Vertrag, die üblicherweise auf der Grundlage der Projektstrategie des Käufers festgelegt wird. Der Leitfaden umfasst nicht:
– kaufmännische, vertragliche oder rechtliche Elemente, die üblicherweise in der Anfrage separat behandelt werden;
– die Zuweisung von Verantwortlichkeiten, die im Vertrag festzulegen sind.
Der Leitfaden beschreibt nicht die Zusammenstellung der Dokumente in der Anfrage.
ANMERKUNG Eine umfassende europäische Umweltpolitik ist in Vorbereitung. Der Leitfaden berücksichtigt deshalb keine Umweltaspekte hinsichtlich der Ausrüstung.
Architecture unifiée OPC - Partie 8: Accès aux données (IEC 62541-8:2015)
La présente norme fournit des recommandations pour la rédaction de la spécification technique nécessaire à l’acquisition d’équipement destiné aux centrales de production d’électricité (centrales électriques). Ce Guide d’achat n’est pas applicable à ce type d’équipement lorsque celui-ci est destiné à la zone d’installation du réacteur des centrales nucléaires. D’autres applications possibles de ce type d’équipement n’ont pas été prises en considération dans la préparation du présent Guide.
Le présent Guide sur le câblage traite d’une grande variété d’activités et peut être utilisé pour tout ou partie de ces activités, en choisissant les parties appropriées, telles que:
- la fourniture du support de câble;
- la pose du câble;
- la finition des extrémités de câble;
Le présent Guide traite de l’installation de câbles d’alimentation de tension au plus égale à 20,8/36 (42) kV, ainsi que de la fourniture et de l’installation de câbles d’instrumentation. La fourniture de câbles d’alimentation est traitée par la EN 45510 2 8.
Le présent Guide englobe l’installation de câbles conducteurs de protection destinés à la mise à la terre et à la liaison équipotentielle vers la ou les bornes principales de terre, à l’exception du réseau de prises de terre enterrées.
L’équipement traité dans le présent Guide est défini plutôt par sa fonction que par son type de conception. Par conséquent, les recommandations relatives à l’établissement de la spécification sont exprimées en termes de performances plutôt que par une description détaillée de l’équipement à fournir.
Le présent Guide indique aux acheteurs potentiels la manière dont il convient qu’ils rédigent leur spécification, afin que
- le type et la capacité de l’équipement soient compatibles avec les autres éléments des systèmes environnants,
- les performances prévues soient atteintes,
- les équipements auxiliaires soient correctement dimensionnés,
- les exigences en termes de fiabilité, de disponibilité et de sécurité soient satisfaites,
- l’attention appropriée soit accordée au processus d’évaluation et aux mesures de qualité à appliquer.
Le présent Guide ne définit pas le genre de la spécification (par exemple spécification détaillée, spécification rédigée en termes de performances, de fonctionnalités) ni l’étendue de la fourniture pour un contrat donné. Ceci relève de la stratégie retenue par l’acheteur pour le projet. Il ne couvre pas
- les aspects commerciaux, contractuels ou légaux, qui sont normalement traités dans d’autres parties du dossier de consultation,
- l’attribution des responsabilités, qui relève du contrat.
Le présent Guide n’impose pas l’arrangement des documents au sein du dossier de consultation.
NOTE La politique européenne globale dans le domaine de l’environnement étant toujours en préparation, le présent Guide ne traite pas des implications environnementales de l’équipement.
Enotna arhitektura OPC - 8. del: Dostop do podatkov (IEC 62541-8:2015)
Ta del standarda IEC 62451 je del niza standardov enotne arhitekture OPC (OPC UA) in določa informacijski model, povezan z dostopom do podatkov. Zajema še zlasti dodatne vrste spremenljivk in dopolnilne opise razredov vozlišč ter atributov, ki so potrebni za dostop do podatkov, dodatne lastnosti in druge informacije in delovanja.
Celoten model naslovnega prostora z vsemi razredi vozlišč in atributi je naveden v standardu IEC 62541-3. Opravila za zaznavanje podatkov in dostop do njih so določena v standardu IEC 62541-4.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 62541-8:2015
01-september-2015
1DGRPHãþD
SIST EN 62541-8:2012
Enotna arhitektura OPC - 8. del: Dostop do podatkov (IEC 62541-8:2015)
OPC Unified Architecture - Part 8: Data Access (IEC 62541-8:2015)
OPC Unified Architecture - Teil 8: Zugriff auf Automatisierungsdaten (IEC 62541-8:2015)
Architecture unifiée OPC - Partie 8: Accès aux données (IEC 62541-8:2015)
Ta slovenski standard je istoveten z: EN 62541-8:2015
ICS:
25.040.40 Merjenje in krmiljenje Industrial process
industrijskih postopkov measurement and control
35.240.50 Uporabniške rešitve IT v IT applications in industry
industriji
SIST EN 62541-8:2015 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 62541-8:2015
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SIST EN 62541-8:2015
EUROPEAN STANDARD EN 62541-8
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2015
ICS 25.040.40; 35.100 Supersedes EN 62541-8:2011
English Version
OPC unified architecture - Part 8: Data Access
(IEC 62541-8:2015)
Architecture unifiée OPC - Partie 8: Accès aux données OPC Unified Architecture - Teil 8: Zugriff auf
(IEC 62541-8:2015) Automatisierungsdaten
(IEC 62541-8:2015)
This European Standard was approved by CENELEC on 2015-04-29. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2015 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN 62541-8:2015 E
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SIST EN 62541-8:2015
EN 62541-8:2015 - 2 -
Foreword
The text of document 65E/381/CDV, future edition 2 of IEC 62541-8, prepared by SC 65E "Devices
and integration in enterprise systems", of IEC/TC 65 "Industrial-process measurement, control and
automation" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as
EN 62541-8:2015.
The following dates are fixed:
• latest date by which the document has to be implemented at (dop) 2016-01-29
national level by publication of an identical national
standard or by endorsement
(dow) 2018-04-29
• latest date by which the national standards conflicting with
the document have to be withdrawn
This document supersedes EN 62541-8:2011.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such
patent rights.
This document has been prepared under a mandate given to CENELEC by the European Commission
and the European Free Trade Association, and supports essential requirements of EU Directive(s).
Endorsement notice
The text of the International Standard IEC 62541-8:2015 was approved by CENELEC as a European
Standard without any modification.
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SIST EN 62541-8:2015
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Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
NOTE 1 When an International Publication has been modified by common modifications, indicated by (mod),
the relevant EN/HD applies.
NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is
available here: www.cenelec.eu.
Publication Year Title EN/HD Year
IEC/TR 62541-1 - OPC unified architecture - CLC/TR 62541-1 -
Part 1: Overview and concepts
IEC 62541-3 - OPC unified architecture - EN 62541-3 -
Part 3: Address Space Model
IEC 62541-4 - OPC Unified Architecture - EN 62541-4 -
Part 4: Services
IEC 62541-5 - OPC unified architecture - EN 62541-5 -
Part 5: Information Model
UNECE 20 - Codes for Units of Measure Used in - -
International Trade
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SIST EN 62541-8:2015
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SIST EN 62541-8:2015
IEC 62541-8
®
Edition 2.0 2015-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
OPC Unified Architecture –
Part 8: Data Access
Architecture unifiée OPC –
Partie 8: Accès aux données
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 25.040.40; 35.100 ISBN 978-2-8322-2273-7
Warning! Make sure that you obtained this publication from an authorized distributor.
Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.
® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
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SIST EN 62541-8:2015
– 2 – IEC 62541-8:2015 © IEC 2015
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references. 6
3 Terms, definitions and abbreviations . 6
3.1 Terms and definitions . 6
3.2 Abbreviations and symbols . 7
4 Concepts . 7
5 Model . 8
5.1 General . 8
5.2 SemanticsChanged . 9
5.3 Variable Types . 9
5.3.1 DataItemType . 9
5.3.2 AnalogItemType . 10
5.3.3 DiscreteItemType . 11
5.3.4 ArrayItemType . 13
5.4 Address Space model . 18
5.5 Attributes of DataItems . 19
5.6 DataTypes . 20
5.6.1 Overview . 20
5.6.2 Range . 20
5.6.3 EUInformation . 20
5.6.4 ComplexNumberType . 21
5.6.5 DoubleComplexNumberType . 22
5.6.6 AxisInformation . 22
5.6.7 AxisScaleEnumeration . 23
5.6.8 XVType . 23
6 Data Access specific usage of Services . 23
6.1 General . 23
6.2 PercentDeadband . 24
6.3 Data Access status codes . 24
6.3.1 Overview . 24
6.3.2 Operation level result codes . 24
6.3.3 LimitBits . 26
Figure 1 – OPC DataItems are linked to automation data . 8
Figure 2 – DataItem VariableType hierarchy . 9
Figure 3 – Graphical view of a YArrayItem . 15
Figure 4 – Representation of DataItems in the AddressSpace . 19
Table 1 – DataItemType definition . 9
Table 2 – AnalogItemType definition . 10
Table 3 – DiscreteItemType definition . 11
Table 4 – TwoStateDiscreteType definition . 12
Table 5 – MultiStateDiscreteType definition . 12
Table 6 – MultiStateValueDiscreteType definition . 13
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Table 7 – ArrayItemType definition . 14
Table 8 – YArrayItemType definition . 14
Table 9 – YArrayItem item description . 15
Table 10 – XYArrayItemType definition . 16
Table 11 – ImageItemType definition . 17
Table 12 – CubeItemType definition . 17
Table 13 – NDimensionArrayItemType definition . 18
Table 14 – Range DataType structure . 20
Table 15 – Range definition . 20
Table 16 – EUInformation DataType structure . 20
Table 17 – EUInformation definition . 20
Table 18 – Examples from the UNECE Recommendation . 21
Table 19 – ComplexNumberType DataType structure . 22
Table 20 – ComplexNumberType definition . 22
Table 21 – DoubleComplexNumberType DataType structure . 22
Table 22 – DoubleComplexNumberType definition . 22
Table 23 – AxisInformation DataType structure . 22
Table 24 – AxisScaleEnumeration values . 23
Table 25 – AxisScaleEnumeration definition . 23
Table 26 – XVType DataType structure . 23
Table 27 – XVType definition . 23
Table 28 – Operation level result codes for BAD data quality . 25
Table 29 – Operation level result codes for UNCERTAIN data quality . 25
Table 30 – Operation level result codes for GOOD data quality . 25
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INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPC UNIFIED ARCHITECTURE –
Part 8: Data Access
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62541-8 has been prepared by subcommittee 65E: Devices and
integration in enterprise systems, of IEC technical committee 65: Industrial-process
measurement, control and automation.
This second edition cancels and replaces the first edition published in 2011. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) Clarified that deadband has to be between 0.0 and 100.0. Violations result in error
Bad_DeadbandFilterInvalid (6.2)
b) Added VariableTypes handling ArrayItems and DataTypes supporting this, including
complex number types. These data types are required for complex analyzer devices but
seem useful for other domains as well.
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SIST EN 62541-8:2015
IEC 62541-8:2015 © IEC 2015 – 5 –
The text of this standard is based on the following documents:
CDV Report on voting
65E/381/CDV 65E/407/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of the IEC 62541 series, published under the general title OPC Unified
Architecture, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
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OPC UNIFIED ARCHITECTURE –
Part 8: Data Access
1 Scope
This part of IEC 62451 is part of the overall OPC Unified Architecture (OPC UA) standard
series and defines the information model associated with Data Access (DA). It particularly
includes additional VariableTypes and complementary descriptions of the NodeClasses and
Attributes needed for Data Access, additional Properties, and other information and
behaviour.
The complete address space model, including all NodeClasses and Attributes is specified in
IEC 62541-3. The services to detect and access data are specified in IEC 62541-4.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC TR 62541-1, OPC Unified Architecture - Part 1: Overview and Concepts
IEC 62541-3, OPC unified architecture - Part 3: Address Space Model
IEC 62541-4, OPC unified architecture - Part 4: Services
IEC 62541-5, OPC unified architecture - Part 5: Information Model
UN/CEFACT: UNECE Recommendation N° 20, Codes for Units of Measure Used in
International Trade, available at http://www.unece.org/cefact/recommendations/rec_index.htm
3 Terms, definitions and abbreviations
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC TR 62541-1,
IEC 62541-3, and IEC 62541-4 as well as the following apply.
3.1.1
DataItem
link to arbitrary, live automation data, that is, data that represents currently valid information
Note 1 to entry: Examples of such data are
• device data (such as temperature sensors),
• calculated data,
• status information (open/closed, moving),
• dynamically-changing system data (such as stock quotes),
• diagnostic data.
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IEC 62541-8:2015 © IEC 2015 – 7 –
3.1.2
AnalogItem
DataItems that represent continuously-variable physical quantities (e.g., length, temperature),
in contrast to the digital representation of data in discrete items
Note 1 to entry: Typical examples are the values provided by temperature sensors or pressure sensors. OPC UA
defines a specific VariableType to identify an AnalogItem. Properties describe the possible ranges of AnalogItems.
3.1.3
DiscreteItem
DataItems that represent data that may take on only a certain number of possible values (e.g.,
OPENING, OPEN, CLOSING, CLOSED)
Note 1 to entry: Specific VariableTypes are used to identify DiscreteItems with two states or with multiple states.
Properties specify the string values for these states.
3.1.4
ArrayItem
DataItems that represent continuously-variable physical quantities and where each individual
data point consists of multiple values represented by an array (e.g., the spectral response of
a digital filter)
Note 1 to entry: Typical examples are the data provided by analyser devices. Specific VariableTypes are used to
identify ArrayItem variants.
3.1.5
EngineeringUnits
units of measurement for AnalogItems that represent continuously-variable physical quantities
(e.g., length, mass, time, temperature)
Note 1 to entry: This standard defines Properties to inform about the unit used for the DataItem value and about
the highest and lowest value likely to be obtained in normal operation.
3.2 Abbreviations and symbols
DA Data Access
EU Engineering Unit
UA Unified Architecture
4 Concepts
Data Access deals with the representation and use of automation data in Servers.
Automation data can be located inside the Server or on I/O cards directly connected to the
Server. It can also be located in sub-servers or on other devices such as controllers and
input/output modules, connected by serial links via field buses or other communication links.
OPC UA Data Access Servers provide one or more OPC UA Data Access Clients with
transparent access to their automation data.
The links to automation data instances are called DataItems. Which categories of automation
data are provided is completely vendor-specific. Figure 1 illustrates how the AddressSpace of
a Server might consist of a broad range of different DataItems.
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OPC UA Server
Root
Adressspace
with DataItems
IEC
Figure 1 – OPC DataItems are linked to automation data
Clients may read or write DataItems, or monitor them for value changes. The Services needed
for these operations are specified in IEC 62541-4. Changes are defined as a change in status
(quality) or a change in value that exceeds a client-defined range called a Deadband. To
detect the value change, the difference between the current value and the last reported value
is compared to the Deadband.
5 Model
5.1 General
The DataAccess model extends the variable model by defining VariableTypes. The
DataItemType is the base type. ArrayItemType, AnalogItemType and DiscreteItemType (and
its TwoState and MultiState subtypes) are specializations. See Figure 2. Each of these
VariableTypes can be further extended to form domain or server specific DataItems.
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IEC 62541-8:2015 © IEC 2015 – 9 –
BaseDataVariableType
Defined in
IEC 62541-5
Type DataItemType
ArrayItemType AnalogItemType DiscreteItemType
TwoState MultiState MultiStateValue
DiscreteType DiscreteType DiscreteType
IEC
Figure 2 – DataItem VariableType hierarchy
5.2 SemanticsChanged
The StatusCode also contains an informational bit called SemanticsChanged.
Servers that implement Data Access shall set this Bit in notifications if certain Properties
defined in this standard change. The corresponding Properties are specified individually for
each VariableType.
Clients that use any of these Properties should re-read them before they process the data
value.
5.3 Variable Types
5.3.1 DataItemType
This VariableType defines the general characteristics of a DataItem. All other DataItem Types
derive from it. The DataItemType derives from the BaseDataVariableType and therefore
shares the variable model as described in IEC 62541-3 and IEC 62541-5. It is formally defined
in Table 1.
Table 1 – DataItemType definition
Attribute Value
BrowseName DataItemType
IsAbstract False
ValueRank −2 (−2 = ‘Any’)
DataType BaseDataType
References NodeClass BrowseName DataType TypeDefinition ModellingRule
Subtype of the BaseDataVariableType defined in IEC 62541-5; i.e the Properties of that type are inherited.
HasSubtype VariableType AnalogItemType Defined in 5.3.2
HasSubtype VariableType DiscreteItemType Defined in 5.3.3
HasSubtype VariableType ArrayItemType Defined in 5.3.4
HasProperty Variable Definition String PropertyType Optional
HasProperty Variable ValuePrecision Double PropertyType Optional
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Definition is a vendor-specific, human readable string that specifies how the value of this
DataItem is calculated. Definition is non-localized and will often contain an equation that can
be parsed by certain clients.
Example: Definition::= “(TempA – 25) + TempB”
ValuePrecision specifies the maximum precision that the Server can maintain for the item
based on restrictions in the target environment.
ValuePrecision can be used for the following DataTypes:
• For Float and Double values it specifies the number of digits after the decimal place.
• For DateTime values it indicates the minimum time difference in nanoseconds. For
example, a ValuePrecision of 20 000 000 defines a precision of 20 ms.
The ValuePrecision Property is an approximation that is intended to provide guidance to a
Client. A Server is expected to silently round any value with more precision that it supports.
This implies that a Client may encounter cases where the value read back from a Server
differs from the value that it wrote to the Server. This difference shall be no more than the
difference suggested by this Property.
5.3.2 AnalogItemType
This VariableType defines the general characteristics of an AnalogItem. All other AnalogItem
Types derive from it. The AnalogItemType derives from the DataItemType. It is formally
defined in Table 2.
Table 2 – AnalogItemType definition
Attribute Value
BrowseName AnalogItemType
IsAbstract False
ValueRank −2 (−2 = ‘Any’)
DataType Number
References NodeClass BrowseName DataType TypeDefinition ModellingRule
Subtype of the DataItemType defined in 5.3.1 i.e the Properties of that type are inherited.
HasProperty Variable InstrumentRange Range PropertyType Optional
HasProperty Variable EURange Range PropertyType Mandatory
HasProperty Variable EngineeringUnits EUInformation PropertyType Optional
The following paragraphs describe the Properties of this VariableType. If the analog item’s
Value contains an array, the Properties shall apply to all elements in the array.
InstrumentRange defines the value range that can be returned by the instrument.
Example: InstrumentRange::= {-9999.9, 9999.9}
Although defined as optional, it is strongly recommended for Servers to support this Property.
Without an InstrumentRange being provided, Clients will commonly assume the full range
according to the DataType.
The Range Data Type is specified in 5.6.2.
EURange defines the value range likely to be obtained in normal operation. It is intended for
such use as automatically scaling a bar grap
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