ISO 9110-1:2020

INTERNATIONAL ISO
STANDARD 9110-1
Second edition
2020-05
Hydraulic fluid power — Measurement
techniques —
Part 1:
General measurement principles
Transmissions hydrauliques — Techniques de mesurage —
Partie 1: Principes généraux de mesurage
Reference number
©
ISO 2020
© ISO 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

Contents Page
Foreword .iv
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Uncertainty of limit specifications . 2
4.1 General aspects . 2
4.2 Classes of measurement accuracy . 2
5 General measurement considerations and requirements . 2
5.1 Calibration . 2
6 Complete calibration procedure . 5
6.1 Selection of reference standard . 5
6.2 Procedure . 5
7 Instrument calibration uncertainty models . 6
7.1 General . 6
7.2 General procedure . 6
7.3 First order uncertainty model . 7
7.4 First order calibration uncertainty evaluation . 7
7.5 Second order uncertainty model . 7
7.6 Second order calibration uncertainty evaluation . 8
7.7 Third order uncertainty model . 8
7.8 Third order calibration uncertainty evaluation . 9
8 Readability uncertainty evaluation .10
8.1 General .10
8.2 Analog readout devices.10
8.3 Digital readout devices .12
8.4 Readout device records .12
9 Assurance control techniques .13
10 Total measurement uncertainty .13
10.1 Determination of measurement system uncertainty .13
Annex A (informative) Measurement system acceptance designated information sheet .14
Annex B (informative) Uncertainty propagation .15
Annex C (informative) Best practices tutorial .16
Bibliography .20
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 131, Fluid power systems, Subcommittee
SC 8, Product testing.
This second edition cancels and replaces the first edition (ISO 9110-1:1990), which has been technically
revised.
The main changes compared to the previous edition are:
— new normative and informative references have been added;
— new definitions have been added;
— classes of accuracy to measurement have been renamed;
— assessment of uncertainties has been revised and expanded and general measurement considerations
and requirements have been renamed;
— guidance on gravity correction has been added;
— readability uncertainty evaluation has been added;
— determination of uncertainty limits and classification of uncertainties has been combined and
uncertainty limit specifications have been renamed;
— frequency of calibration has been revised and assurance control techniques have been renamed;
— total measurement uncertainty clause has been added;
— original Annex A has been deleted;
— new Annex A - Measurement System Acceptance Designated Information Sheet, has been added;
— new Annex B - Uncertainty Propagation, has been added;
iv © ISO 2020 – All rights reserved

— new Annex C - Best Practices Tutorial, has been added.
A list of all parts in the ISO 9110 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
Introduction
Universal measurement standards are required if meaningful comparisons are to be made and valid
conclusions deduced. A fundamental aspect of fluid power technology is the need to quantify the
performance characteristics of hydraulic components and systems to provide a basis for action or
decision-making. The method of measurement used is capable of reliably determining such performance
characteristics.
This document provides guidance for identifying uncertainty sources and magnitudes in the calibration
of instruments and their use in measurement situations encountered in hydraulic fluid power testing.
Methods are described for assessing the uncertainty in measurements and derived results.
It is widely recognized that no measurement, irrespective of the amount of care exercised, can ever
be absolutely accurate and free of error. Different circumstances each have unique uncertainty
requirements. The value of a measurement is dictated by the use that will be made of it, as well as the
particular circumstance. Therefore, the maximum value of a reported measure can only be realized if
it can be applied under many different circumstances, requiring that the uncertainty associated with a
measure be assessed and reported.
This document is intended to be used in conjunction with others that address the measurement of
specific physical parameters: flow, pressure, torque, speed and temperature.
This document (ISO 9110-1) relates to general principles for the measurement of static or steady-state
conditions. ISO 9110-2 deals with the measurement of average steady-state static pressure in a closed
conduit.
vi © ISO 2020 – All rights reserved

INTERNATIONAL STANDARD ISO 9110-1:2020(E)
Hydraulic fluid power — Measurement techniques —
Part 1:
General measurement principles
1 Scope
This document establishes general principles for the measurement of performance parameters under
static or steady-state conditions.
This document provides guidance on the sources and magnitudes of uncertainty to be expected in
the calibration of and measurements using hydraulic fluid power components. It describes practical
requirements for assessing the capability of the measuring system, and hence the level of uncertainty
of the measurement system, or for assisting in developing a system which will meet a prescribed level
of uncertainty.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 5598, Fluid power systems and components — Vocabulary
ISO 7870-1, Control charts — Part 1: General guidelines
ISO 7870-2, Control charts — Part 2: Shewhart control charts
ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
me a s ur ement (GUM: 1995)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5598 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
data reduction errors
errors that stem from any processing of test data to the final result, as from digital computer resolution,
numerical rounding of results, and uncertainty in model curve fitting and interp
...

INTERNATIONAL ISO
STANDARD 9110-1
Second edition
2020-05
Hydraulic fluid power — Measurement
techniques —
Part 1:
General measurement principles
Transmissions hydrauliques — Techniques de mesurage —
Partie 1: Principes généraux de mesurage
Reference number
©
ISO 2020
© ISO 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

Contents Page
Foreword .iv
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Uncertainty of limit specifications . 2
4.1 General aspects . 2
4.2 Classes of measurement accuracy . 2
5 General measurement considerations and requirements . 2
5.1 Calibration . 2
6 Complete calibration procedure . 5
6.1 Selection of reference standard . 5
6.2 Procedure . 5
7 Instrument calibration uncertainty models . 6
7.1 General . 6
7.2 General procedure . 6
7.3 First order uncertainty model . 7
7.4 First order calibration uncertainty evaluation . 7
7.5 Second order uncertainty model . 7
7.6 Second order calibration uncertainty evaluation . 8
7.7 Third order uncertainty model . 8
7.8 Third order calibration uncertainty evaluation . 9
8 Readability uncertainty evaluation .10
8.1 General .10
8.2 Analog readout devices.10
8.3 Digital readout devices .12
8.4 Readout device records .12
9 Assurance control techniques .13
10 Total measurement uncertainty .13
10.1 Determination of measurement system uncertainty .13
Annex A (informative) Measurement system acceptance designated information sheet .14
Annex B (informative) Uncertainty propagation .15
Annex C (informative) Best practices tutorial .16
Bibliography .20
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 131, Fluid power systems, Subcommittee
SC 8, Product testing.
This second edition cancels and replaces the first edition (ISO 9110-1:1990), which has been technically
revised.
The main changes compared to the previous edition are:
— new normative and informative references have been added;
— new definitions have been added;
— classes of accuracy to measurement have been renamed;
— assessment of uncertainties has been revised and expanded and general measurement considerations
and requirements have been renamed;
— guidance on gravity correction has been added;
— readability uncertainty evaluation has been added;
— determination of uncertainty limits and classification of uncertainties has been combined and
uncertainty limit specifications have been renamed;
— frequency of calibration has been revised and assurance control techniques have been renamed;
— total measurement uncertainty clause has been added;
— original Annex A has been deleted;
— new Annex A - Measurement System Acceptance Designated Information Sheet, has been added;
— new Annex B - Uncertainty Propagation, has been added;
iv © ISO 2020 – All rights reserved

— new Annex C - Best Practices Tutorial, has been added.
A list of all parts in the ISO 9110 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
Introduction
Universal measurement standards are required if meaningful comparisons are to be made and valid
conclusions deduced. A fundamental aspect of fluid power technology is the need to quantify the
performance characteristics of hydraulic components and systems to provide a basis for action or
decision-making. The method of measurement used is capable of reliably determining such performance
characteristics.
This document provides guidance for identifying uncertainty sources and magnitudes in the calibration
of instruments and their use in measurement situations encountered in hydraulic fluid power testing.
Methods are described for assessing the uncertainty in measurements and derived results.
It is widely recognized that no measurement, irrespective of the amount of care exercised, can ever
be absolutely accurate and free of error. Different circumstances each have unique uncertainty
requirements. The value of a measurement is dictated by the use that will be made of it, as well as the
particular circumstance. Therefore, the maximum value of a reported measure can only be realized if
it can be applied under many different circumstances, requiring that the uncertainty associated with a
measure be assessed and reported.
This document is intended to be used in conjunction with others that address the measurement of
specific physical parameters: flow, pressure, torque, speed and temperature.
This document (ISO 9110-1) relates to general principles for the measurement of static or steady-state
conditions. ISO 9110-2 deals with the measurement of average steady-state static pressure in a closed
conduit.
vi © ISO 2020 – All rights reserved

INTERNATIONAL STANDARD ISO 9110-1:2020(E)
Hydraulic fluid power — Measurement techniques —
Part 1:
General measurement principles
1 Scope
This document establishes general principles for the measurement of performance parameters under
static or steady-state conditions.
This document provides guidance on the sources and magnitudes of uncertainty to be expected in
the calibration of and measurements using hydraulic fluid power components. It describes practical
requirements for assessing the capability of the measuring system, and hence the level of uncertainty
of the measurement system, or for assisting in developing a system which will meet a prescribed level
of uncertainty.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 5598, Fluid power systems and components — Vocabulary
ISO 7870-1, Control charts — Part 1: General guidelines
ISO 7870-2, Control charts — Part 2: Shewhart control charts
ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
me a s ur ement (GUM: 1995)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5598 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
data reduction errors
errors that stem from any processing of test data to the final result, as from digital computer resolution,
numerical rounding of results, and uncertainty in model curve fitting and interp
...