IEC 61069-4:2016

Industrial-process measurement, control and automation - Evaluation of system properties for the purpose of system assessment - Part 4: Assessment of system performance

IEC 61069-4:2016 specifies the detailed method of the assessment of performance of a basic control system (BCS) based on the basic concepts of IEC 61069-1 and methodology of IEC 61069-2, defines basic categorization of performance properties, describes the factors that influence performance and which need to be taken into account when evaluating performance, and provides guidance in selecting techniques from a set of options (with references) for evaluating the performance. This second edition cancels and replaces the first edition published in 1997. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
- Reorganization of the material of IEC 61069-4:1997 to make the overall set of standards more organized and consistent;
- IEC TS 62603-1:2014 has been incorporated into this edition.

Mesure, commande et automation dans les processus industriels - Appréciation des propriétés d'un système en vue de son évaluation - Partie 4: Évaluation des caractéristiques de fonctionnement d'un système

L'IEC 61069-4:2016 spécifie la méthode d'évaluation détaillée des caractéristiques de fonctionnement d'un système de commande de base (BCS) reposant sur les principes de base de l'IEC 61069-1 et la méthodologie de l'IEC 61069-2; définit la classification de base des propriétés des caractéristiques de fonctionnement; décrit les facteurs ayant une influence sur les caractéristiques de fonctionnement et qui doivent être pris en compte lors de l'appréciation des caractéristiques de fonctionnement; donne des lignes directrices concernant les techniques de sélection à partir d'un ensemble d'options (avec références) pour l'appréciation des caractéristiques de fonctionnement. Cette deuxième édition annule et remplace la première édition parue en 1997. Cette édition constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
- Réorganisation des informations contenues dans l'IEC 61069-4:1997 visant à mieux organiser l'ensemble complet de normes et à le rendre plus cohérent;
- L'IEC TS 62603-1:2014 a été incorporée dans cette édition.

General Information

• Status: Published
• Publication Date: 14-Jun-2016
• ICS: 25.040.40 - Industrial process measurement and control
• ICS: 29.120.50 - Fuses and other overcurrent protection devices
• Technical Committee: SC 65A - System aspects
• Drafting Committee: WG 16 - TC 65/SC 65A/WG 16
• Current Stage: PPUB - Publication issued
• Start Date: 15-Jun-2016
• Completion Date: 15-Jul-2016

Relations

• Revises: IEC 61069-4:1997 - Industrial-process measurement and control - Evaluation of system properties for the purpose of system assessment - Part 4: Assessment of system performance
• Effective Date: 05-Sep-2023

Overview

IEC 61069-4:2016 is an international standard developed by the International Electrotechnical Commission (IEC) focusing on the assessment of system performance in industrial-process measurement, control, and automation. This standard outlines detailed methods to evaluate the performance of Basic Control Systems (BCS), building upon the foundational concepts from IEC 61069-1 and the methodologies from IEC 61069-2. The document specifically addresses categorizing performance properties, considering factors influencing performance, and offers guidance on selecting appropriate evaluation techniques.

This edition from 2016 replaces the original 1997 version, introducing significant improvements such as reorganization for improved clarity and the integration of IEC TS 62603-1:2014, which enhances consistency across the IEC 61069 series.

Key Topics

• Performance Properties
  The standard details the core performance metrics essential for system assessment, including:

  • Accuracy - The degree to which the measured or controlled value conforms to the true or intended value.
  • Response Time - The time duration the system takes to respond to input or changes.
  • Capacity - The system's ability to handle specific operational loads or functions under varying conditions.

• Factors Influencing Performance
  IEC 61069-4 stresses the evaluation of variables that affect performance, such as environmental conditions, system design, communication delays, and hardware/software limitations.

• Assessment Methodology
  The document provides a structured approach:

  • Defining assessment objectives.
  • Designing and planning the assessment program.
  • Executing systematic tests and measurements.
  • Reporting clear, actionable results to aid decision-making.

• Evaluation Techniques
  Two primary techniques are outlined:

  • Analytical Techniques - Using mathematical and theoretical models to predict performance.
  • Empirical Techniques - Conducting physical tests and measurements to assess real-world system behavior.

• Supporting Checklists and Models
  Annexes include comprehensive checklists for system requirements and design, examples of assessment items, and schematic models to assist practitioners in implementation.

Applications

IEC 61069-4:2016 is vital for industries leveraging automated control systems where reliable and measurable performance is critical. Application areas include:

• Process Control Systems in Manufacturing
  Ensuring accuracy and responsiveness to maintain high quality and efficiency in production lines.

• Automation in Energy and Utilities
  Assessing system capacity and performance ensures stability and safety in power generation and distribution.

• Water and Wastewater Treatment Plants
  Evaluating control system response time helps optimize process cycles and resource usage.

• Chemical and Petrochemical Industries
  Rigorous performance assessment minimizes risk by ensuring system accuracy and timely reaction under critical conditions.

• Safety Instrumented Systems (SIS)
  Structured performance evaluation contributes to compliance with safety regulations and reliable emergency responses.

By aligning system assessment with IEC 61069-4 protocols, engineers and system integrators can systematically improve reliability, optimize control strategies, and enhance overall operational efficiency.

Related Standards

IEC 61069-4:2016 is part of the broader IEC 61069 series dedicated to system property evaluation for industrial automation:

• IEC 61069-1: Basic concepts of evaluation systems for industrial-process control systems.
• IEC 61069-2: Methodology of system assessments.
• IEC TS 62603-1:2014: Incorporated within IEC 61069-4, providing complementary assessment methodologies.

These interconnected standards collectively provide a comprehensive framework to assess and improve industrial measurement and control systems, supporting global harmonization and best practices in automation technology.

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Keywords: IEC 61069-4, industrial-process measurement, control system performance, system assessment, basic control system, accuracy evaluation, response time, capacity analysis, industrial automation standards, IEC standards, performance evaluation techniques.

Standards Content (Sample)

IEC 61069-4 ®
Edition 2.0 2016-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Industrial-process measurement, control and automation – Evaluation of system
properties for the purpose of system assessment –
Part 4: Assessment of system performance

Mesure, commande et automation dans les processus industriels – Appréciation
des propriétés d'un système en vue de son évaluation –
Partie 4: Évaluation des caractéristiques de fonctionnement d’un système

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IEC 61069-4 ®
Edition 2.0 2016-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Industrial-process measurement, control and automation – Evaluation of system

properties for the purpose of system assessment –

Part 4: Assessment of system performance

Mesure, commande et automation dans les processus industriels – Appréciation

des propriétés d'un système en vue de son évaluation –

Partie 4: Évaluation des caractéristiques de fonctionnement d’un système

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 25.040.40 ISBN 978-2-8322-3408-2

– 2 – IEC 61069-4:2016 © IEC 2016
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 8
2 Normative references. 8
3 Terms, definitions, abbreviated terms, acronyms, conventions and symbols . 9
3.1 Terms and definitions . 9
3.2 Abbreviated terms, acronyms, conventions and symbols . 9
4 Basis of assessment specific to performance . 9
4.1 Performance properties . 9
4.1.1 General . 9
4.1.2 Accuracy . 10
4.1.3 Response time . 10
4.1.4 Capacity . 10
4.2 Factors influencing performance . 11
5 Assessment method . 12
5.1 General . 12
5.2 Defining the objective of the assessment . 12
5.3 Design and layout of the assessment . 12
5.4 Planning of the assessment program . 12
5.5 Execution of the assessment . 12
5.6 Reporting of the assessment . 12
6 Evaluation techniques . 13
6.1 General . 13
6.2 Analytical evaluation techniques . 13
6.3 Empirical evaluation techniques. 13
6.3.1 General topics . 13
6.3.2 Tests to evaluate accuracy . 14
6.3.3 Tests to evaluate response time . 15
6.3.4 Tests to evaluate capacity . 15
6.4 Additional topics for evaluation techniques . 15
Annex A (informative) Checklist and example of SRD for system performance . 16
Annex B (informative) Check list and/or example of SSD for system performance . 19
B.1 SSD information . 19
B.2 Check points for system performance . 19
Annex C (informative) An example of a list of assessment items (information from
IEC TS 62603-1) . 20
C.1 Overview. 20
C.2 Accuracy – Time performances of the BCS . 20
C.2.1 Absolute time synchronisation . 20
C.2.2 Requirements of the time stamping . 20
C.3 Response time . 21
C.3.1 Overall response time of the BCS . 21
C.3.2 Switch-over time for redundant CPUs . 21
C.3.3 Real-time constraints for control functions . 21
C.3.4 Controller cyclic time . 21

C.3.5 Time constraints for display . 22
C.3.6 Call-up time . 22
C.3.7 Video screen page refresh time . 22
Annex D (informative) Model of an evaluation . 23
D.1 General . 23
D.2 Analytical evaluation techniques . 25
D.2.1 General . 25
D.2.2 Accuracy . 25
D.2.3 Response time . 25
D.2.4 Capacity . 26
D.3 Empirical evaluation techniques. 26
D.3.1 General . 26
D.3.2 Accuracy . 26
D.3.3 Response time/capacity . 28
D.4 Precautions . 31
Bibliography . 32

Figure 1 – General layout of IEC 61069 . 7
Figure 2 – Performance . 9
Figure D.1 – Schematic functional diagram of a system . 23
Figure D.2 – Generic physical system model . 25

Table A.1 – SRD performance checklist . 16
Table C.1 – Resolution and discrimination time . 21

– 4 – IEC 61069-4:2016 © IEC 2016
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INDUSTRIAL-PROCESS MEASUREMENT, CONTROL AND AUTOMATION –
EVALUATION OF SYSTEM PROPERTIES FOR
THE PURPOSE OF SYSTEM ASSESSMENT –

Part 4: Assessment of system performance

FOREWORD
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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 61069-4 has been prepared by subcommittee 65A: System
aspects, of IEC technical committee 65: Industrial-process measurement, control and
automation.
This second edition cancels and replaces the first edition published in 1997. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) Reorganization of the material of IEC 61069-4:1997 to make the overall set of standards
more organized and consistent;
b) IEC TS 62603-1:2014 has been incorporated into this edition.

The text of this standard is based on the following documents:
FDIS Report on voting
65A/792/FDIS 65A/801/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 in the IEC 61069 series, published under the general title Industrial-process
measurement, control and automation – Evaluation of system properties for the purpose of
system assessment, 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.
– 6 – IEC 61069-4:2016 © IEC 2016
INTRODUCTION
IEC 61069 deals with the method which should be used to assess system properties of a
basic control system (BCS). IEC 61069 consists of the following parts:
Part 1: Terminology and basic concepts
Part 2: Assessment methodology
Part 3: Assessment of system functionality
Part 4: Assessment of system performance
Part 5: Assessment of system dependability
Part 6: Assessment of system operability
Part 7: Assessment of system safety
Part 8: Assessment of other system properties
Assessment of a system is the judgement, based on evidence, of the suitability of the system
for a specific mission or class of missions.
To obtain total evidence would require complete evaluation (for example under all influencing
factors) of all system properties relevant to the specific mission or class of missions.
Since this is rarely practical, the rationale on which an assessment of a system should be
based is:
– the identification of the importance of each of the relevant system properties;
– the planning for evaluation of the relevant system properties with a cost-effective
dedication of effort to the various system properties.
In conducting an 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.
An assessment can only be carried out if a mission has been stated (or given), or if any
mission can be hypothesized. In the absence of a mission, no assessment can be made;
however, evaluations can still be specified and carried out for use in assessments performed
by others. In such cases, IEC 61069 can be used as a guide for planning an evaluation and it
provides methods for performing evaluations, since evaluations are an integral part of
assessment.
In preparing the assessment, it can be discovered that the definition of the system is too
narrow. For example, a facility with two or more revisions of the control systems sharing
resources, for example a network, should consider issues of co-existence and inter-operability.
In this case, the system to be investigated should not be limited to the “new” BCS; it should
include both. That is, it should change the boundaries of the system to include enough of the
other system to address these concerns.
The part structure and the relationship among the parts of IEC 61069 are shown in Figure 1.

IEC 61069: Industrial-process measurement, control and automation –
Evaluation of system properties for the purpose of system assessment
Part 1: Terminology and basic concepts
• Basic concept
• Terminology ‐ Objective
‐ Description of system
‐ Common terms
‐ Terms for particular part
‐ System properties
‐ Influencing factors
Part 2: Assessment methodology
• Generic requirements of procedure of assessment
‐ Overview, approach and phases
‐ Requirements for each phase
‐ General description of evaluation techniques
Parts 3 to 8: Assessment of each system property
• Basics of assessment specific to each property
‐ Properties and influencing factors
• Assessment method for each property
• Evaluation techniques for each property

IEC
Figure 1 – General layout of IEC 61069
Some example assessment items are integrated in Annex C.

– 8 – IEC 61069-4:2016 © IEC 2016
INDUSTRIAL-PROCESS MEASUREMENT, CONTROL AND AUTOMATION –
EVALUATION OF SYSTEM PROPERTIES FOR
THE PURPOSE OF SYSTEM ASSESSMENT –

Part 4: Assessment of system performance

1 Scope
This part of IEC 61069:
– specifies the detailed method of the assessment of performance of a basic control system
(BCS) based on the basic concepts of IEC 61069-1 and methodology of IEC 61069-2,
– defines basic categorization of performance properties,
– describes the factors that influence performance and which need to be taken into account
when evaluating performance, and
– provides guidance in selecting techniques from a set of options (with references) for
evaluating the performance.
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 60068 (all parts), Environmental testing
IEC 60654 (all parts), Industrial-process measurement and control equipment – Operating
conditions
IEC 60721 (all parts), Classification of environmental conditions
IEC 61000 (all parts), Electromagnetic compatibility (EMC)
IEC 61069-1:— , Industrial-process measurement, control and automation – Evaluation of
system properties for the purpose of system assessment – Part 1: Terminology and basic
concepts
IEC 61069-2:— , Industrial-process measurement, control and automation – Evaluation of
system properties for the purpose of system assessment – Part 2: Assessment methodology
IEC 61326 (all parts), Electrical equipment for measurement, control and laboratory use –
EMC requirements
_____________
Second edition to be published simultaneously with this part of IEC 61069.
Second edition to be published simultaneously with this part of IEC 61069.

3 Terms, definitions, abbreviated terms, acronyms, conventions and symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 61069-1 apply.
3.2 Abbreviated terms, acronyms, conventions and symbols
For the purposes of this document, the abbreviated terms, acronyms, conventions and
symbols given in IEC 61069-1 apply.
4 Basis of assessment specific to performance
4.1 Performance properties
4.1.1 General
A system is expected to be able to perform tasks required by the system mission with
accuracy and within a specified response time. If the system executes several tasks, it
handles these tasks without obstructing the execution of the other tasks. Hence capacity,
which indicates the number of tasks which can be executed within a time frame, is important.
To assess the performance of a system it is therefore necessary to categorise system
properties in a hierarchical way.
Performance properties are categorized as shown in Figure 2.
Performance
Accuracy Response time Capacity
IEC
Figure 2 – Performance
Performance cannot be assessed directly and cannot be described by a single property.
Performance can only be determined by analysis and testing of each of performance
properties individually.
To be able to determine the system performance properties it is necessary to analyze the
system in terms of information translations.
It is necessary to examine the system performance properties for each of the information
translations in the system.
It should be noted that the system performance properties can be mutually dependent.
When a system accomplishes several tasks, the performance can vary, and for each of the
relevant tasks a separate analysis is required.
Performance should be described for each task, which is represented by an information
translation, with specified conditions for the other tasks concurrently operating.

– 10 – IEC 61069-4:2016 © IEC 2016
4.1.2 Accuracy
Accuracy indicates closeness of agreement between the specified and the realized
information translation executed by the system under defined conditions.
The accuracy of an information translation function includes potentially many system
properties, for example:
– hysteresis,
– dead band,
– repeatability error,
– resolution.
4.1.3 Response time
Response time indicates the time interval between the initiation of an information translation
and the instant when the associated response is made available under defined conditions.
An information translation function generally comprises the following functional steps:
– information collection, which depends on the time constant of input filters (hard and/or
software) and input cycle times;
– information processing, which depends on the processing cycle time;
– output actuation, which depends on the times of output filters (hard and/or software) and
output cycle times.
Each of the above functional steps of an information translation function can be executed in a
synchronous or asynchronous way.
Attention should be paid to the fact that the overall response time of an information translation
is not simply the sum of the time spent for functional steps, due to interdependencies. For
example, new initiation can coincide in time with a running information translation resulting in
an increase in response time.
The response time differs with respect to each information translation, and depends on
priority settings of concurrent tasks, cycle time settings, activated credibility mechanisms, etc.
The response time can be quantified for individual tasks. In some cases, the value calculated
may contain a degree of uncertainty and that should be recorded with the value, for example
50 % ± 10 % or 50 % with a 90 % certainty.
4.1.4 Capacity
Capacity is a property of the system performance which indicates the maximum number of
information translations of a given information translation function which the system is able to
execute within a defined period of time, without negatively impacting any other system
capabilities.
The capacity of a system depends on the amount of calculation capability, the available
storage, and the available I/O bandwidth.
For a given system, the capacity (maximum load) is fixed. Capacity can only be changed
through additions or changes to the given system. The following are some concepts of interest:
Capacity = base load + operating load + spare capacity

A system is at maximum load when there is no spare capacity available. Overload occurs
when the user-defined tasks do not operate in the designed time frame due to resource
restrictions.
The evaluation of the system capacity should be done by checking that the spare capacity is
available under that operating load as specified in the SRD. The assessment will ensure that
the spare capacity is available under that operating load.
4.2 Factors influencing performance
The performance of a system can be affected by the influencing factors listed in IEC 61069-
1:—, 5.3.
For each of the system performance properties listed in 4.1, the primary influencing factors
are as follows:
Accuracy can be affected by influencing factors originating from:
– the environment, such as ambient temperature;
– infrastructure, such as voltage variations and surges expected from the main power
supply;
– electrical noise, such as pick-up by in-coming and out-going lines from and to field-
mounted equipment, due to earthing problems, and/or conducted and/or radiated
electro-magnetic interferences;
– time exposed to temperature and heat radiation;
– humidity;
– vibration.
Accuracy should be tested over at least the total range to which the system will be subjected.
Response time is mainly affected by conditions originating in the tasks, such as:
– increase in activities (e.g. an alarm burst);
– externally generated interruptions, for example from the main power supply, and/or
from electrical noise.
Capacity and spare capacity are affected by:
– increase in activities (e.g. an alarm burst);
– enhancing the system;
– externally generated interruptions, for example from the main power supply, and/or
from electrical noise;
– loss of memory due to poor memory management.
In general, any deviations from the operating conditions specified can affect the performance
of the system.
When specifying tests to evaluate the effects of influencing factors, the following International
standards shall be consulted:
– IEC 60068;
– IEC 60721;
– IEC 60654;
– IEC 61000;
– IEC 61326.
– 12 – IEC 61069-4:2016 © IEC 2016
5 Assessment method
5.1 General
The assessment shall follow the method as laid down in IEC 61069-2:—, Clause 5.
5.2 Defining the objective of the assessment
Defining the objective of the assessment shall follow the method as laid down in IEC 61069-
2:—, 5.2.
5.3 Design and layout of the assessment
Design and layout of the assessment shall follow the method as laid down in IEC 61069-2:—,
5.3.
Defining the scope of assessment shall follow the method laid down in IEC 61069-2:—, 5.3.1.
Collation of documented information shall be conducted in accordance with IEC 61069-2:—,
5.3.3.
The statements compiled in accordance with IEC 61069-2:—, 5.3.3, should include the
following in addition to the items listed in IEC 61069-2:—, 5.3.3:
– the required task(s) as defined in the SRD, and the information translation functions
provided by the system to support these;
– the location of the end points of each information translation function.
Documenting collated information shall follow the method in IEC 61069-2:—, 5.3.4.
Selecting assessment items shall follow IEC 61069-2:—, 5.3.5.
Assessment specification should be developed in accordance with IEC 61069-2:—, 5.3.6.
Comparison of the SRD and the SSD shall follow IEC 61069-2:—, 5.3.
NOTE 1 A checklist of the SRD for system dependability is provided in Annex A.
NOTE 2 A checklist of the SSD for system dependability is provided in Annex B.
5.4 Planning of the assessment program
Planning the assessment program shall follow the method as laid down in IEC 61069-2:—, 5.4.
Assessment activities shall be developed in accordance with IEC 61069-2:—, 5.4.2.
The final assessment program should specify the points specified in IEC 61069-2:—, 5.4.3.
5.5 Execution of the assessment
The execution of the assessment shall be in accordance with IEC 61069-2:—, 5.5.
5.6 Reporting of the assessment
The reporting of the assessment shall be in accordance with IEC 61069-2:—, 5.6.
The report shall include information specified in IEC 61069-2:—, 5.6. Additionally, the
assessment report should address the following points:

– No additional items are noted.
6 Evaluation techniques
6.1 General
Within IEC 61069-4, several evaluation techniques are suggested. Other methods may be
applied but, in all cases, the assessment report should provide references to documents
describing the techniques used.
Those evaluation techniques are categorized as described in IEC 61069-2:—, Clause 6.
NOTE An example of a list of assessment items is provided in Annex C.
Factors influencing system performance properties as per 4.2 shall be taken into account.
The techniques as given in 6.2, 6.3 and 6.4 are recommended to evaluate system
performance properties.
6.2 Analytical evaluation techniques
An analytical evaluation is a qualitative analysis of the system configuration complemented
with quantification of the basic performance properties of the elements.
In order to evaluate performance properties, it is recommended to use models which
represent the way in which the elements are used to implement the required information
translations.
The same model can be used to infer system performance from the evaluation of the
performance of the individual elements.
An example of such a model is developed in Annex D.
The model, representing the performance aspects, shows the information translations, the
elements used and their interconnection.
Basic quantified performance data are added to each of the elements shown in the model.
These quantitative data can be obtained from generic data, system documentation, and data
obtained from evaluations of the elements and/or a detailed analysis of the design of the
elements. The data used shall be those applicable for the range of influencing factors for
which the evaluation is required.
The values on accuracy, response time and capacity are then obtained by inference, based
upon the individual specification of the modules and elements and the chaining of these to
support the information translations.
A more refined method of analyzing the performance properties can be made by the
construction of a simulation model of the analytical model described above, simulating
random agitation of the input channels and recording the outputs, traffic on busses, etc.
6.3 Empirical evaluation techniques
6.3.1 General topics
Although it is often feasible to conduct an empirical evaluation, (also called a test) in isolated
individual modules and elements within an information translation function, these tests do not
often provide sufficient data on the performance of the task(s) required. Such tests can only
be performed at the boundary of each information translation.

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The design of these tests should be guided by a qualitative analysis of the system, and based
on a selected task or set of tasks which represents the performance of the information
translation function. At least one test should be conducted for each class of information
translation functions such as:
– process measurement indication (e.g. analogue, digital);
– process control action;
– keyboard manipulated process action;
– keyboard manipulated display call-up;
– refreshment of displayed data;
– alarm monitor;
– time recording;
– communications link;
– feedback of manipulated values (e.g. indication, correcting device).
In general, each performance test of a particular information translation should be executed
with the conditions of the other information translation(s) at those as given in the SRD.
The performance of a system is affected by influencing factors as stated in 4.2.
6.3.2 Tests to evaluate accuracy
For the purpose of evaluating/measuring the accuracy, the information translations can be
categorized into two types of information translations.
a) Time-independent information translations
A guidance on measuring the accuracy of time-independent information translations can
be found in IEC 61298-2.
Information translations, which can partly be treated as time-independent are, for example:
– measurement and indication of process values (e.g. analogue, digital, counter type);
– output of manipulated values;
– feedback of manipulated values (e.g. indication, correcting device).
b) Time-dependent information translations
Time-dependent information translations include mostly time-independent parts. It is
advisable to separately evaluate or measure the accuracy of these parts before the overall
accuracy of the information translation is evaluated.
Accuracy of process control action(s) in a system should be evaluated using process
simulation.
The objective of evaluating the overall accuracy is principally to check:
– whether the system internal image of all statuses and values of the process reflects the
current real-time situation of the process at each moment in time, and is complete and
consistent;
NOTE 1 This could be tested by stimulating each input after another and checking whether its contents in the
process image contains the correct value and/or status.
– whether the internal system times of each element are identical, have the same resolution
and are equal to the local time;
NOTE 2 This could be tested by extracting and displaying the current day and time on all relevant modules
and elements and comparing those with each other and with the local time.
– whether the resolution of the system internal time is able to identify, note and correctly
time stamp the sequence of fast changes in the values and statuses of the same or
different event(s);
NOTE 3 This could be evaluated by stimulating in a chronological order a set of inputs with a defined number
of events per second and noting the timestamp, status and value changes in the process image.
– whether the resolution of the system internal time is able to identify, note and correctly
time stamp the sequence of fast changes in the values and statuses of the same or
different event(s).
NOTE 4 That could be evaluated by stimulating in a chronological order a set of inputs with a defined number
of events per second and noting the timestamp, status and value changes in the process image.
The accuracy of each information translation should be tested from the source to the
destination of the information at the system boundaries.
The results, for each class of information translation, should be expressed as an average of
the results obtained from a series of tests, with the translation tolerances stated.
6.3.3 Tests to evaluate response time
The tests should measure the response time of the information translations under
consideration from the source to the destination of the information.
The results should be expressed as an average of the time periods obtained over a series of
tests, with the translation tolerances stated, for each class of information translation.
Effects obtained on the results because of special conditions, such as change-over to a
stand-by controller, should be separately stated.
6.3.4 Tests to evaluate capacity
The tests should measure the capacity of the system. This should be executed for each class
of information translation. The measured capacity should be evaluated as to whether it is
enough for the expected task, taking into account the base load of the system.
Where data and event recording and storage are key functions, tests should address any
deterioration of capacity over time due to poor memory management.
During these tests, the other information translations should be kept constant at the values
required in the SRD.
For each of the values precise and detailed information should be given of the conditions
under which these have been obtained, such as:
– the nature and volume of each of the information translations, whether these are refreshed
periodically or by exception, the effects of buffering, etc.;
– the effects of the occurrence of random system tasks on the results, for example change-
over to a stand-by controller, request of a report, an alarm burst, etc.
The results should be expressed as an average of the results obtained from a series of tests,
with the translation tolerances stated, for each class of information translation.
6.4 Additional topics for evaluation techniques
No additional items are noted.

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Annex A
(informative)
Checklist and example of SRD for system performance

The matrix in Table A.1 provides an example check list of the type of information (task by task
and/or information translation) which should be given in the SRD for the purpose of
performance assessment.
It should be checked whether the performance requirements are stated under specific
operating conditions, for example, steady state, bursts of input information, etc., for each of
the system tasks.
These requirements should have been provided both in relation to individual tasks as well as
in relation to the total mission.
Table A.1 – SRD performance checklist (1 of 3)
Performance SRD
property items Performance specification
General Description of tasks supported by:
• process control and measurement diagram
• description of the control and measurement requirements in support
of each task
• operational and monitoring requirements of each task
• importance of task for mission
• a plot showing suggested location of measurement and control points, operators
control desk/panel, etc.
Sizing parameters Number of operator consoles:
• 2 triple, 1 double and 5 single screen consoles
Extent of process control and measurement requirements:
• measured values (direct connected) 900
• measured values (tele
...