EN 61069-1:1993

SLOVENSKI STANDARD
01-november-1998
Industrial-process measurement and control - Evaluation of system properties for
the purpose of system assessment - Part 1: General considerations and
methodology (IEC 61069-1:1991)
Industrial-process measurement and control - Evaluation of system properties for the
purpose of system assessment -- Part 1: General considerations and methodology
Leittechnik für industrielle Prozesse - Ermittlung der Systemeigenschaften zum Zweck
der Eignungsbeurteilung eines Systems -- Teil 1: Allgemeine Überlegungen und
Methodik
Mesure et commande dans les processus industriels - Appréciation des propriétés d'un
système en vue de son évaluation -- Partie 1: Considérations générales et méthodologie
Ta slovenski standard je istoveten z: EN 61069-1:1993
ICS:
25.040.40 Merjenje in krmiljenje Industrial process
industrijskih postopkov measurement and control
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

NORME
CEI
INTERNATIONALE IEC
61069-1
INTERNATIONAL
Première édition
STANDARD
First edition
1991-09
Mesure et commande dans les processus
industriels –
Appréciation des propriétés d'un système
en vue de son évaluation –
Partie 1:
Considérations générales et méthodologie
Industrial -
process measurement and control –
Evaluation of system properties for
the purpose of system assessment –
Part 1:
General considerations and methodology
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1069-1 ©IEC - 3 -
CONTENTS
Page
FOREWORD 5
INTRODUCTION 9
Clause
1 Scope 11
2 Definitions 11
3 Basis of an assessment 13
4 Assessment considerations 15
5 Assessment procedures 25
Figures
1 Model of industrial-process measurement and control systems 33
2 System properties 35
3 - Domains of influencing conditi
ons 37
4 - Influencing conditions 39
5 - Assessment matrix 41
1069-1 ©IEC - 5 -
INTERNATIONAL ELECTROTECHNICAL COMMISSION
INDUSTRIAL-PROCESS MEASUREMENT AND CONTROL -
EVALUATION OF SYSTEM PROPERTIES FOR
THE PURPOSE OF SYSTEM ASSESSMENT
Part 1: General considerations and methodology
FOREWORD
1) The formal decisions or agreements of the IEC on technical matters, prepared by Technical Committees on
which all the National Committees having a special interest therein are represented, express, as nearly as
possible, an international consensus of opinion on the subjects dealt with.
2) They have the form of recommendations for international use and they are accepted by the National
Committees in that sense.
In order to promote international unification, the IEC expresses the wish that all National Committees
3)
should adopt the text of the IEC recommendation for their national rules in so far as national conditions will
permit. Any divergence between the IEC recommendation and the corresponding national rules should, as
far as possible, be clearly indicated in the latter.
This part of the International Standard IEC 1069 has been prepared by Sub-
Committee 65A: System aspects, of IEC Technical Committee No. 65: Industrial-process
measurement and control.
The text of this pa
rt is based on the following documents:
Six Months' Rule Report on Voting
65A(CO)20 65A(CO)23
Full information on the voting for the approval of this part can be found in the Voting
Report
indicated in the above table.
The complete standard will consist of a series of publications, of which this is the first part.
Part 1 provides the overall guidance and as such it is intended as a "stand-alone" publi-
cation.
Part 2 details the assessment methodology.
Part
s 3 to 8 provide guidance on the assessment of specific groups of properties.

1069-1 ©IEC - 7 -
The division of properties in Parts 3 to 8 has been chosen so as to group together related
properties.
The complete series will consist of the following titles:
Part 1: General considerations and methodology.
Part 2: Assessment methodology (under consideration).
Part 3: Assessment of system functionality (under consideration).
Part 4: Assessment of system performance (under consideration).
Part 5: Assessment of system dependability (under consideration).
Part 6: Assessment of system operability (under consideration).
Part
7: Assessment of system safety (under consideration).
Part 8: Assessment of non-task-related system properties (under consideration).

1069-1 © IEC -9-
INTRODUCTION
This part of IEC 1069 provides methods and procedures for the assessment of industrial-
process measurement and control systems.
Assessment of a system is judgement, based on evidence, of a system's suitability for a
specific mission or class of missions.
To obtain total evidence would require complete (i.e. under all influencing conditions)
evaluation of all system properties of relevance to the specific mission or class of
missions.
Since this is rarely practical, the rationale for an assessment of a system is:
- to identify the criticality of the relevant system properties;
- to plan for the evaluation of the relevant system properties with a cost-effective
dedication of e
ffort to the various properties.
In conducting the assessment of a system, it is crucial to bear in mind the need to gain a
maximum increase in confidence in the suitability of a system within practical cost and
time constraints.
This part
of IEC 1069, together with existing International Standards dealing with the eva-
luation of
system-elements as individual entities, provides methods and procedures for the
assessment of a system as a whole.

1069-1 © IEC - 11 -
INDUSTRIAL-PROCESS MEASUREMENT AND CONTROL -
EVALUATION OF SYSTEM PROPERTIES FOR
THE PURPOSE OF SYSTEM ASSESSMENT
Part 1: General considerations and methodology
1 Scope
of IEC 1069 outlines the general considerations in the assessment of industrial-
This part
process measurement and control systems, hereafter referred to as "system(s)".
This part, together with subsequent parts, is intended for the users and manufacturers of
systems, and also for those who are responsible for carrying out assessments as an inde-
pendent party.
2 Definitions
2.1 Unless otherwise stated, the definitions in the following documents apply:
IEC 50(351): 1975, International Electrotechnical Vocabulary (1EV) - Chapter 351: Auto-
matic control.
IEC 271: 1974, List of basic terms, definitions and related mathematics for reliability.
IEC 271A: 1978, Litt of basic terms, definitions and related mathematics for reliability.
First supplement.
IEC 271B: 1983, List of basic terms, definitions and related mathematics for reliability.
Second supplement.
IEC 271C: 1985,
List of basic terms, definitions and related mathematics for reliability.
Third supplement.
2.2 For the purpose of this part of IEC 1069 the following definitions apply.
2.2.1 assessment (of
a system): Judgement, based on evidence, of the system's suita-
bility for a specific mission or class of missions.
2.2.2 evaluation (of a system property): Attribution of a qualitative or quantitative
value to that system property.
2.2.3 mission (of a system): Collective activity assigned to the system to achieve a
defined goal in a defined period under defined conditions.
2.2.4 task: Logically complete operation forming a pa
rt of the system mission.
1069-1 ©IEC - 13 -
2.2.5 function: Elementary operation performed by the system which, combined with
other elementary operations (system functions), enables the system to perform a task.
2.2.6 module: Discrete unit, capable of performing distinct functions and which can be
easily joined to or arranged with other units.
2.2.7 element: Any physical pa , comprising hardware and/or software, that can be indi-
rt
vidually considered and tested.
3 Basis of an assessment
The purpose of the assessment of a system is to determine qualitatively and/or quantitati-
vely the capability of that system to accomplish a specific mission.
Assessment of a system is judgement, based on evidence, of a system's suitability for a
specific mission or class of missions.
To obtain total evidence would require complete (i.e. under all influencing conditions) eva-
luation of all system properties of relevance to the specific mission or class of missions.
Since this is rarely practical, the rationale for an assessment of a system shall be:
- to identify the criticality of the relevant system properties to accomplish the mission;
- to plan for evaluation of the relevant system properties with a cost effective dedica-
tion of effort to the various properties.
In conducting the assessment of a system, it is crucial to bear in mind the need to gain a
maximum increase in confidence in the suitability of a system within practical cost and
time constraints.
To accomplish a mission, a system shall be capable of performing the tasks necessary to
support the mission, such as regulating pressures or flows, optimizing reactor conditions,
etc.
The system shall provide the functions to enable these tasks to be performed. Such
functions are, for example, those for measuring flows, storing data and displaying pictures.
These functions are implemented in system elements. An element may be a piece of hard-
ware, an orifice plate, an analogue to digital convertor, or a piece of software performing a
flow calculation, storing a picture-image, etc.
Industrial-process measurement and control systems perform the tasks required, using the
available functions and elements in various configurations.
This characteristic of the system makes it difficult to synthesize the capability of a system
to fulfil a specific task by evaluating the characteristics of the individual constituent
functions and elements alone.
- 15 -
1069-1 © IEC
This part of IEC 1069 outlines a method to assess such systems using other appropriate
standards and guides, where these are available.
rt
To facilitate the assessment of a system, this pa of IEC 1069 segregates the properties
of a system in related groups.
This is especially useful in those cases where not all aspects need to be, or can be,
evaluated. The boundaries of the system to be assessed shall be well-defined and the
conditions at these boundaries examined.
These conditions can influence the behaviour of the system.
The extent of the assessment of a system largely depends on the mission and boundaries
of the system, the influencing conditions and the objective of the assessment.
This part of IEC 1069 provides a method for organizing the assessment of systems.
The scope of the assessment can be conveniently summarized in the form of a matrix,
listing on one axis the system properties and on the other axis the influencing conditions
to be considered. The cells of this matrix can be used to note which of the influencing
conditions is to be considered for each system property.
4 Assessment considerations
4.1 Objectives
The objectives of the assessment shall be clearly stated prior to the start of the assess-
ment as a foundation for planning the assessment programme. The objectives have a
large impact on the nature and depth of the assessment.
A system may be so complex that comprehensive evaluations of all system properties
would not be cost-effective, or even feasible. By careful consideration of the objectives,
the system architecture and the influencing conditions, the evaluations can be reduced to
include only those items which are most sensitive for the system application.
The objectives of the assessment should be documented carefully prior to the preparation
of the assessment programme and should be used as a basis for the guiding principles
throughout the assessment period.
The objectives of the assessment may be:
to assess a specific system for a particular application;
to compare several systems for a particular application;
to obtain an assessment of a particular system for general use in a variety of appli-
cations.
For each type of assessment, a specific system configuration or architecture and a set of
system properties and influencing conditions need to be evaluated.

1069-1 ©IEC - 17 -
4.2
The system
A system accomplishes its mission by means of the interaction of its modules, each with
its own properties. These modules are either centralized in one location or decentralized
in several locations.
The capability of a system to accomplish the mission objective cannot be assessed by
synthesizing the data obtained from evaluations of the properties of the individual system
modules and elements only. The assessments and evaluations of individual modules can
provide useful and perhaps necessary inputs to the assessment of a system.
Many of the system properties are derived from the interaction of the modules and hence
do not exist for the modules in isolation; therefore a full assessment can only be made by
considering the system as a whole.
For structuring the system, a functional model provides a u
...