Maize - Determination of moisture content (on milled grains and on whole grains) (ISO 6540:2021)

This document specifies two methods:
— a reference method for the determination of the moisture content of maize grains and ground whole
maize, groats, grits and maize flour, see Clause 4;
— a routine method for the evaluation of the moisture content of maize in whole grains, see Clause 5.
The latter is not suitable for use for experts’ reports, or for calibration or checking of humidity meters,
because of its significant bias to the reference method (see Table B.3).

Mais - Bestimmung des Feuchtegehalts (von gemahlenen und ganzen Körnern) (ISO 6540:2021)

Dieses Dokument legt zwei Verfahren fest:
- ein Referenzverfahren zur Bestimmung des Feuchtegehalts von ganzen Maiskörnern und gemahlenem Vollmais, Grobgrieß, Feingrieß und Maismehl, siehe Abschnitt 4;
- ein Routineverfahren zur Bewertung des Feuchtegehalts von ganzen Maiskörnern, siehe Abschnitt 5.
Das letztgenannte Verfahren ist wegen seiner signifikanten systematischen Abweichungskomponente gegenüber dem Referenzverfahren (siehe Tabelle B.3) nicht zur Anwendung für Fachberichte oder für die Kalibrierung oder Überprüfung von Feuchtemessgeräten geeignet.

Maïs - Détermination de la teneur en eau (sur grains broyés et sur grains entiers) (ISO 6540:2021)

Le présent document spécifie deux méthodes:
- une méthode de référence pour la détermination de la teneur en eau des grains de maïs et de la mouture de maïs entier, des gruaux et de la farine de maïs; voir l'Article 4;
- une méthode pratique pour l'évaluation de la teneur en eau des grains de maïs, en opérant sur les grains entiers; voir l'Article 5.
Cette dernière ne convient ni pour des expertises ni pour l'étalonnage ou le contrôle des humidimètres en raison de son biais important par rapport à la méthode de référence (voir le Tableau B.3).

Koruza - Določevanje vlage (v zmletih in celih zrnih) (ISO 6540:2021)

General Information

Status
Published
Public Enquiry End Date
19-May-2020
Publication Date
15-Apr-2021
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
11-Mar-2021
Due Date
16-May-2021
Completion Date
16-Apr-2021

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SLOVENSKI STANDARD
SIST EN ISO 6540:2021
01-maj-2021
Nadomešča:
SIST EN ISO 6540:2010
Koruza - Določevanje vlage (v zmletih in celih zrnih) (ISO 6540:2021)

Maize - Determination of moisture content (on milled grains and on whole grains) (ISO

6540:2021)
Mais - Bestimmung des Feuchtegehalts (von gemahlenen und ganzen Körnern) (ISO
6540:2021)

Maïs - Détermination de la teneur en eau (sur grains broyés et sur grains entiers) (ISO

6540:2021)
Ta slovenski standard je istoveten z: EN ISO 6540:2021
ICS:
67.060 Žita, stročnice in proizvodi iz Cereals, pulses and derived
njih products
SIST EN ISO 6540:2021 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 6540:2021
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SIST EN ISO 6540:2021
EN ISO 6540
EUROPEAN STANDARD
NORME EUROPÉENNE
March 2021
EUROPÄISCHE NORM
ICS 67.060 Supersedes EN ISO 6540:2010
English Version
Maize - Determination of moisture content (on milled
grains and on whole grains) (ISO 6540:2021)

Maïs - Détermination de la teneur en eau (sur grains Mais - Bestimmung des Feuchtegehalts (von

broyés et sur grains entiers) (ISO 6540:2021) gemahlenen und ganzen Körnern) (ISO 6540:2021)

This European Standard was approved by CEN on 13 February 2021.

CEN 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 CEN

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 CEN member into its own language and notified to the CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 6540:2021 E

worldwide for CEN national Members.
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SIST EN ISO 6540:2021
EN ISO 6540:2021 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 6540:2021
EN ISO 6540:2021 (E)
European foreword

This document (EN ISO 6540:2021) has been prepared by Technical Committee CEN/TC 338 "NA" in

collaboration with Technical Committee CEN/TC 338 “Cereal and cereal products” the secretariat of

which is held by AFNOR.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by September 2021, and conflicting national standards

shall be withdrawn at the latest by September 2021.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN shall not be held responsible for identifying any or all such patent rights.

This document supersedes EN ISO 6540:2010.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,

Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of

North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the

United Kingdom.
Endorsement notice

The text of ISO 6540:2021 has been approved by CEN as EN ISO 6540:2021 without any modification.

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SIST EN ISO 6540:2021
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SIST EN ISO 6540:2021
INTERNATIONAL ISO
STANDARD 6540
Second edition
2021-02
Maize — Determination of moisture
content (on milled grains and on
whole grains)
Maïs — Détermination de la teneur en eau (sur grains broyés et sur
grains entiers)
Reference number
ISO 6540:2021(E)
ISO 2021
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SIST EN ISO 6540:2021
ISO 6540:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

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
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
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SIST EN ISO 6540:2021
ISO 6540:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Reference method ............................................................................................................................................................................................... 1

4.1 Principle ........................................................................................................................................................................................................ 1

4.2 Apparatus .................................................................................................................................................................................................... 1

4.3 Sampling ....................................................................................................................................................................................................... 2

4.4 Preparation of the test sample .................................................................................................................................................. 2

4.4.1 Products not requiring to be ground .............................................................................................................. 2

4.4.2 Products requiring to be ground ........................................................................................................................ 3

4.5 Procedure .................................................................................................................................................................................................... 3

4.5.1 Number of determinations...................................................................................................................................... 3

4.5.2 Test portion .......................................................................................................................................................................... 3

4.5.3 Drying ........................................................................................................................................................................................ 4

4.5.4 Weighing ................................................................................................................................................................................. 4

4.6 Expression of results .......................................................................................................................................................................... 4

4.7 Precision ....................................................................................................................................................................................................... 5

4.7.1 Interlaboratory test ....................................................................................................................................................... 5

4.7.2 Repeatability ....................................................................................................................................................................... 5

4.7.3 Reproducibility .................................................................................................................................................................. 5

4.7.4 Comparison of two groups of measurements in a laboratory .................................................. 5

4.7.5 Comparison of two groups of measurements in two laboratories ....................................... 5

4.7.6 Uncertainty ........................................................................................................................................................................... 6

4.7.7 Comparison with the absolute method ........................................................................................................ 6

4.8 Notes on procedure ............................................................................................................................................................................. 6

4.9 Test report ................................................................................................................................................................................................... 6

5 Routine method on whole grains ........................................................................................................................................................ 7

5.1 Principle ........................................................................................................................................................................................................ 7

5.2 Apparatus .................................................................................................................................................................................................... 8

5.3 Sampling ....................................................................................................................................................................................................... 8

5.4 Procedure .................................................................................................................................................................................................... 8

5.4.1 Test portion .......................................................................................................................................................................... 8

5.4.2 Drying ........................................................................................................................................................................................ 8

5.4.3 Number of determinations...................................................................................................................................... 8

5.5 Expression of results .......................................................................................................................................................................... 9

5.5.1 Method of calculation and formulae ............................................................................................................... 9

5.5.2 Repeatability ....................................................................................................................................................................... 9

5.5.3 Reproducibility .................................................................................................................................................................. 9

5.5.4 Comparison of two groups of measurements in a laboratory .................................................. 9

5.5.5 Comparison of two groups of measurements in two laboratories ....................................10

5.5.6 Application of fidelity limits................................................................................................................................10

5.6 Remark ........................................................................................................................................................................................................10

5.7 Test report ................................................................................................................................................................................................10

Annex A (informative) Absolute method .......................................................................................................................................................11

Annex B (informative) Interlaboratory test results ...........................................................................................................................18

Annex C (informative) Application of fidelity data for the whole grains method ...............................................24

Bibliography .............................................................................................................................................................................................................................25

© ISO 2021 – All rights reserved iii
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SIST EN ISO 6540:2021
ISO 6540:2021(E)
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 34, Food products, Subcommittee SC 4,

Cereals and pulses, in collaboration with the European Committee for Standardization (CEN) Technical

Committee CEN/TC 338, Cereal and cereal products, in accordance with the Agreement on technical

cooperation between ISO and CEN (Vienna Agreement).

This second edition cancels and replaces the first edition (ISO 6540:1980), which has been technically

revised. The main changes compared with the previous edition are as follows:

— Clauses 7 to 10 and 17 to 20 (now 4.5 to 4.9 and 5.4 to 5.7) and the annexes have been revised.

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.
iv © ISO 2021 – All rights reserved
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SIST EN ISO 6540:2021
ISO 6540:2021(E)
Introduction

The basic reference method and the routine reference method relating to cereals (see ISO 712) are

only applicable to other cereals than maize and cereal products. Therefore, this document has been

[4]

developed to specify the two methods for maize on the basis of research works published in 1979 .

The basic reference method for maize, which is called the “absolute method”, requires special equipment

and experienced personnel, and can only be applied in specialized laboratories.

Due to the very high moisture content that can be present in samples of maize (sometimes greater than

a mass fraction of 40 %) and because of the size and texture of the grains, the determination of the

moisture in maize raises problems with regard to its grinding and pre-drying.

Consequently, to allow the pre-drying and grinding to be avoided, this document also describes a

routine method for whole grains. which is easier to use and allows working in series. Its response time

is longer but the workload is lower, because of the absence of grinding. However, this practical whole

grain method has a positive bias of about a mass fraction of 0, 30 % compared to the reference method.

© ISO 2021 – All rights reserved v
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SIST EN ISO 6540:2021
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SIST EN ISO 6540:2021
INTERNATIONAL STANDARD ISO 6540:2021(E)
Maize — Determination of moisture content (on milled
grains and on whole grains)
1 Scope
This document specifies two methods:

— a reference method for the determination of the moisture content of maize grains and ground whole

maize, groats, grits and maize flour, see Clause 4;

— a routine method for the evaluation of the moisture content of maize in whole grains, see Clause 5.

The latter is not suitable for use for experts’ reports, or for calibration or checking of humidity meters,

because of its significant bias to the reference method (see Table B.3).
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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
moisture content of maize
loss in mass undergone by a product under specified conditions
Note 1 to entry: It is expressed as a percentage.
4 Reference method
4.1 Principle

If necessary, grinding of a sample, after pre-conditioning, if required. Drying of a test portion at a

temperature between 130 °C and 133 °C, under conditions that enable a result to be obtained in

agreement with that obtained by the absolute method (see Annex A).
4.2 Apparatus

4.2.1 Analytical balance, able to weight with an accuracy of ±0,001 g and therefore having a display

accuracy of 0,000 1 g.

4.2.2 Analytical balance, able to weight with an accuracy of ±0,1 g and therefore having a display

accuracy of 0,01 g.
© ISO 2021 – All rights reserved 1
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SIST EN ISO 6540:2021
ISO 6540:2021(E)
4.2.3 Grinding mill, having the following characteristics:
a) made of material that does not absorb moisture;
b) easy to clean and having as little dead space as possible;

c) enabling grinding of 30 g of maize grains to be carried out rapidly and uniformly, without

appreciable development of heat and, as far as possible, without contact with the outside air;

d) adjustable so as to obtain particles of the dimensions indicated in 4.4.1.

4.2.4 Metal boat, without lid, with an effective surface area enabling 100 g of maize grains to be

distributed in a single layer.

4.2.5 Metal capsule, of suitable dimensions, non-corrodible under the test conditions, or, failing this,

a glass dish, with a sufficiently tight-fitting lid, and having an effective surface area such as to allow

distribution of the test portion with no more than 0,3 g per square centimetre.

4.2.6 Constant-temperature oven, electrically heated, adjustable between 60 °C and 80 °C, and with

adequate ventilation.

4.2.7 Constant-temperature oven, electrically heated, capable of being controlled in such a way that

the temperature of the air and of the shelves carrying the test portions is within the range of 130 °C to

133 °C in the neighbourhood of the test portions, in normal working condition.

The oven shall have a heat capacity such that, when initially adjusted to a temperature of 131 °C, it can

again reach this temperature in less than 45 min (preferably in less than 30 min) after insertion of the

maximum number of test portions that can be dried simultaneously.

The effectiveness of the ventilation shall be determined using durum wheat semolina, with a maximum

particle size of 1 mm, as the test material. The ventilation shall be such that, after inserting all the test

portions that the oven can hold and drying at a temperature of 130 °C to 133 °C, the results after a heating

period of 2 h and then a further 1 h will not differ by more than 0,15 g of moisture per 100 g of sample.

4.2.8 Desiccator, containing an efficient desiccant.
4.3 Sampling

Sampling is not part of the method specified in this document. A recommended sampling method is

given in ISO 24333.

The laboratory should be provided with a truly representative sample, in a sealed package, that is

undamaged and unmodified during transport and storage.
4.4 Preparation of the test sample
4.4.1 Products not requiring to be ground

Products that have particles of sizes less than or equal to 1,7 mm, less than a mass fraction of 10 %

being over 1 mm and more than a mass fraction of 50 % being less than 0,5 mm, do not need to be

ground before the determination.
Mix the laboratory sample thoroughly before taking the test portion (see 4.5.3).
2 © ISO 2021 – All rights reserved
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SIST EN ISO 6540:2021
ISO 6540:2021(E)
4.4.2 Products requiring to be ground
4.4.2.1 General

If the laboratory sample does not have the particle size characteristics mentioned in 4.4.1, it shall be

ground either without pre-conditioning (4.4.2.2) or with pre-conditioning (4.4.2.3) as required.

4.4.2.2 Grinding without pre-conditioning

For products that are not likely to undergo variations in moisture content in the course of grinding (in

general, products with a moisture content between a mass fraction of 9,00 % and 15,00 %, see 4.8),

carry out grinding without pre-conditioning.

Adjust the grinding mill (4.2.3) to obtain particles of the dimensions indicated in 4.4.1.

Then quickly grind about 30 g of the laboratory sample, mix with a spatula and proceed immediately as

specified in 4.5.1.
4.4.2.3 Grinding with pre-conditioning

Products that are likely to undergo changes in moisture content in the course of grinding (in general,

products with a moisture content more than a mass fraction of 15,00 % or less than a mass fraction of

9,00 %) shall be pre-conditioned to bring their moisture content to between a mass fraction of 9,00 %

and 15,00 %, see 4.8) before grinding.

If the moisture content is greater than a mass fraction of 15,00 % (which is the more frequent case),

weigh, to the nearest 0,1g, about 100 g of the laboratory sample in the metal boat (4.2.4), place this

in the oven (4.2.7) controlled at between 60 °C and 80 °C, and leave it for the time necessary to bring

the moisture content to between a mass fraction of 9,00 % and 15,00 %. Take the boat out of the oven

and allow it to stand in the laboratory atmosphere for the time necessary (at least 2 h) for the pre-

conditioned sample to return to the laboratory temperature and for the moisture distribution to be

relatively uniform. During this rest, it shall be ensured that no addition or withdrawal of material is

made to the contents of the boat. If necessary, cover it with a sheet of paper but not with a lid, since this

could limit the exchange of moisture between the air and the grain.

After conditioning, weigh the sample to the nearest 0,1 g, then, proceeding rapidly, grind about 30 g of

this product. Mix using a spatula.

If the moisture content is less than a mass fraction of 9,00 %, place about 100 g of the laboratory sample,

weighed to the nearest 0,1 g, in a suitable atmosphere (usually that of the laboratory) and leave it until

a moisture content within the limits specified above is obtained.
4.5 Procedure
4.5.1 Number of determinations
For each laboratory sample, carry out the determination in duplicate.

Carry out one determination on each of the two ground test portions taken from the laboratory sample,

in accordance with 4.5.2 to 4.5.4. If the absolute difference between the two results is greater than the

repeatability limit given in 4.7.2, repeat the determination until the requirements are met.

4.5.2 Test portion

For each sample, tare to the nearest 0,001 g two metal capsules (4.2.5) beforehand. For each capsule,

note the tare t.

Weigh rapidly, to the nearest 0,001 g, approximately (8 ± 1) g of the test sample (see 4.4.1, 4.4.2.2 or

4.4.2.3, as appropriate) into the capsule. Note the mass m′ .
© ISO 2021 – All rights reserved 3
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SIST EN ISO 6540:2021
ISO 6540:2021(E)
4.5.3 Drying

Place the open capsule containing the test portion, and the lid, in the oven (4.2.7) controlled between

130 °C and 133 °C and leave it for 4 h ± 5 min.

Never place moist products in an oven containing test portions at the end of dehydration, nor open the

oven door during drying, nor introduce new wet test samples before removing the dry test portions as

this would rehydrate them.

At the end of the drying time and, proceeding rapidly, take the dish out of the oven, cover it and place it

in the desiccator (4.2.8). When several tests are being carried out simultaneously, never place dishes on

top of one another in the desiccator.
4.5.4 Weighing

When the dish has cooled to laboratory temperature (generally between 30 min and 45 min after it has

been placed in the desiccator), weigh it to the nearest 0,001 g. Note the mass m′ .

4.6 Expression of results

The moisture content, w , expressed as a percentage by mass of the product as received, is given by

H2O
Formulae (1) and (2):
a) without pre-conditioning:
100
w = mm− (1)
H200 1
where
m = m′ – t is the mass, in grams, of the test portion (see 4.5.3);
0 0
m = m′ – t is the mass, in grams, of the test portion after drying (see 4.5.4);
1 1
t is the tare of the capsule, in grams (see 4.5.2).
b) with pre-conditioning:
 
100
wm= −m +−mm (2)
 
H20 01 23
m m
 0  2
 mm 
w =100 1−
 
H20
 
where
m and m have the same signification as in a) above;
0 1
m is the mass, in grams, of the sample before conditioning (see 4.4.2.3);
m is the mass, in grams, of the sample after conditioning (see 4.4.2.3).

Take as the result the average of the two values obtained, provided that the requirement for repeatability

(see 4.7.2) is satisfied. If it is not, repeat the determinations.
Express the result to the second decimal place.
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SIST EN ISO 6540:2021
ISO 6540:2021(E)
4.7 Precision
4.7.1 Interlaboratory test

The details of an interlaboratory test relating to the precision of the method are summarized in

Annex B. Values from this test can only be applied to water content ranges from 11,90 % to 39,20 % and

the studied matrix (maize).
4.7.2 Repeatability

The absolute difference between two independent individual test results, obtained using the same

method on identical material test
...

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