Superconductivity - Part 23: Residual resistance ratio measurement - Residual resistance ratio of Nb superconductors

IEC 61788-23:2018 addresses a test method for the determination of the residual resistance ratio (RRR) of cavity-grade niobium. The test method should be valid for specimens with rectangular or round cross-section, cross-sectional area greater than 1 mm2 but less than 20 mm2, and a length not less than 10 nor more than 25 times the width or diameter.

Supraleitfähigkeit – Teil 23: Messung des Restwiderstandsverhältnisses – Restwiderstandsverhältnis von Nb-Supraleitern

Supraconductivité - Partie 23: Mesurage du rapport de résistance résiduelle - Rapport de résistance résiduelle des supraconducteurs de Nb

IEC 61788-23:2018 spécifie une méthode d'essai pour la détermination du rapport de résistance résiduelle (RRR) du niobium à cavités. Il convient que la méthode d’essai soit valide pour des éprouvettes à sections rectangulaires ou circulaires, de surface de section supérieure à 1 mm2 mais inférieure à 20 mm2, et dont la longueur n’est pas inférieure à 10 fois ni supérieure à 25 fois la largeur ou le diamètre.

Superprevodnost - 23. del: Meritve razmerja preostale upornosti - Razmerje preostale upornosti Nb superprevodnikov (IEC 61788-23:2018)

Ta del standarda IEC 61788 obravnava preskusno metodo za določanje razmerja preostale upornosti (RRR), rRRR, niobija po stopnjah vdolbin. Metoda je predvidena za izjemno čiste vsebnosti niobija z vrednostjo 15 < rRRR < 600. Preskusno metodo je treba uporabljati za vzorce s pravokotnim ali okroglim prečnim prerezom, pri čemer mora biti površina prečnega prereza od 1 mm2 do 20 mm2 in dolžina od 10- do 25-kratna vrednost širine ali premera.

General Information

Status
Withdrawn
Publication Date
09-Oct-2018
Withdrawal Date
09-Jul-2021
Technical Committee
Drafting Committee
Current Stage
6060 - Document made available - Publishing
Start Date
05-Oct-2018
Completion Date
05-Oct-2018

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SLOVENSKI STANDARD
SIST EN IEC 61788-23:2018
01-december-2018
Superprevodnost - 23. del: Meritve razmerja preostale upornosti - Razmerje
preostale upornosti Nb superprevodnikov (IEC 61788-23:2018)
Superconductivity - Part 23: Residual resistance ratio measurement - Residual
resistance ratio of Nb superconductors (IEC 61788-23:2018)
Ta slovenski standard je istoveten z: EN IEC 61788-23:2018
ICS:
17.220.20 0HUMHQMHHOHNWULþQLKLQ Measurement of electrical
PDJQHWQLKYHOLþLQ and magnetic quantities
29.050 Superprevodnost in prevodni Superconductivity and
materiali conducting materials
SIST EN IEC 61788-23:2018 en

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

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SIST EN IEC 61788-23:2018
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SIST EN IEC 61788-23:2018
EUROPEAN STANDARD EN IEC 61788-23
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2018
ICS 17.220; 29.050
English Version
Superconductivity - Part 23: Residual resistance ratio
measurement - Residual resistance ratio of Nb superconductors
(IEC 61788-23:2018)

Supraconductivité - Partie 23: Mesurage du rapport de Supraleitfähigkeit - Teil 23: Messung des

résistance résiduelle - Rapport de résistance résiduelle des Restwiderstandsverhältnisses - Restwiderstandsverhältnis

supraconducteurs de Nb von Nb-Supraleitern
(IEC 61788-23:2018) (IEC 61788-23:2018)

This European Standard was approved by CENELEC on 2018-07-10. CENELEC members are bound to comply with the CEN/CENELEC

Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC

Management Centre or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation

under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the

same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,

Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,

Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden,

Switzerland, Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2018 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.

Ref. No. EN IEC 61788-23:2018 E
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SIST EN IEC 61788-23:2018
EN IEC 61788-23:2018 (E)
European foreword

The text of document 90/400/FDIS, future edition 1 of IEC 61788-23, prepared by IEC/TC 90

"Superconductivity" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as

EN IEC 61788-23:2018.
The following dates are fixed:

• latest date by which the document has to be implemented at national (dop) 2019-04-10

level by publication of an identical national standard or by endorsement

• latest date by which the national standards conflicting with the (dow) 2021-07-10

document have to be withdrawn

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

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

Endorsement notice

The text of the International Standard IEC 61788-23:2018 was approved by CENELEC as a European

Standard without any modification.

In the official version, for Bibliography, the following notes have to be added for the standards

indicated:
IEC 61788-4:2016 NOTE Harmonized as EN 61788-4:2016 (not modified)
IEC 61788-10:2006 NOTE Harmonized as EN 61788-10:2006 (not modified)
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SIST EN IEC 61788-23:2018
EN IEC 61788-23:2018 (E)
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

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.

NOTE 1 Where an International Publication has been modified by common modifications, indicated by (mod), the relevant

EN/HD applies.

NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available here:

www.cenelec.eu.
Publication Year Title EN/HD Year
IEC 60050-815 - International Electrotechnical Vocabulary - - -
Part 815: Superconductivity
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SIST EN IEC 61788-23:2018
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SIST EN IEC 61788-23:2018
IEC 61788-23
Edition 1.0 2018-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Superconductivity –
Part 23: Residual resistance ratio measurement – Residual resistance ratio of Nb
superconductors
Supraconductivité –
Partie 23: Mesurage du rapport de résistance résiduelle – Rapport de résistance
résiduelle des supraconducteurs de Nb
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.220; 29.050 ISBN 978-2-8322-5719-7

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
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SIST EN IEC 61788-23:2018
– 2 – IEC 61788-23:2018 © IEC 2018
CONTENTS

FOREWORD ........................................................................................................................... 4

INTRODUCTION ..................................................................................................................... 6

1 Scope .............................................................................................................................. 7

2 Normative references ...................................................................................................... 7

3 Terms and definitions ...................................................................................................... 7

4 Principle .......................................................................................................................... 8

5 Measurement apparatus .................................................................................................. 9

5.1 Mandrel or base plate ............................................................................................. 9

5.2 Cryostat and support of mandrel or base plate ........................................................ 9

6 Specimen preparation .................................................................................................... 10

7 Data acquisition and analysis ........................................................................................ 11

7.1 Data acquisition hardware ..................................................................................... 11

7.2 Resistance (R ) at room temperature .................................................................... 11

7.3 Residual resistance (R ) just above the superconducting transition ....................... 11

7.4 Validation of the residual resistance measurement ................................................ 13

7.5 Residual resistance ratio ....................................................................................... 13

8 Uncertainty of the test method ....................................................................................... 13

9 Test report ..................................................................................................................... 13

9.1 General ................................................................................................................. 13

9.2 Test information .................................................................................................... 13

9.3 Specimen information ........................................................................................... 13

9.4 Test conditions ..................................................................................................... 14

9.5 RRR value ............................................................................................................ 14

Annex A (Informative) Additional information relating to the measurement of RRR ............... 15

A.1 Considerations for specimens and apparatus ........................................................ 15

A.2 Considerations for specimen mounting orientation ................................................ 16

A.3 Alternative methods for increasing temperature of specimen above

superconducting transition temperature ................................................................ 16

A.3.1 General ......................................................................................................... 16

A.3.2 Heater method ............................................................................................... 16

A.3.3 Controlled methods........................................................................................ 16

A.4 Other test methods ............................................................................................... 16

A.4.1 General ......................................................................................................... 16

A.4.2 Measurement of resistance versus time ......................................................... 17

A.4.3 Comparison of ice point and room temperature .............................................. 17

A.4.4 Extrapolation of the resistance to 4,2 K ......................................................... 17

A.4.5 Use of magnetic field to suppress superconductivity at 4,2 K ......................... 18

A.4.6 AC techniques ............................................................................................... 18

Annex B (informative) Uncertainty considerations ................................................................ 19

B.1 Overview............................................................................................................... 19

B.2 Definitions............................................................................................................. 19

B.3 Consideration of the uncertainty concept .............................................................. 19

B.4 Uncertainty evaluation example for TC 90 standards ............................................. 21

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SIST EN IEC 61788-23:2018
IEC 61788-23:2018 © IEC 2018 – 3 –

Annex C (informative) Uncertainty evaluation for resistance ratio measurement of Nb

superconductors ................................................................................................................... 23

C.1 Evaluation of uncertainty ....................................................................................... 23

C.1.1 Room temperature measurement uncertainty ................................................. 23

C.1.2 Cryogenic measurement uncertainty .............................................................. 24

C.1.3 Estimation of uncertainty for typical experimental conditions .......................... 26

C.2 Round robin test summary .................................................................................... 26

Bibliography .......................................................................................................................... 28

Figure 1 – Relationship between temperature and resistance near the superconducting

transition ................................................................................................................................. 8

Figure A.1 – Determination of the value of R from a resistance versus time plot .................. 17

Figure C.1 – Graphical description of the uncertainty of regression related to the

measurement of R ............................................................................................................... 25

Table B.1 – Output signals from two nominally identical extensometers ................................ 20

Table B.2 – Mean values of two output signals ..................................................................... 20

Table B.3 – Experimental standard deviations of two output signals ...................................... 20

Table B.4 – Standard uncertainties of two output signals ...................................................... 21

Table B.5 – Coefficient of variations of two output signals ..................................................... 21

Table C.1 – Uncertainty of measured parameters ................................................................. 26

Table C.2 – RRR values obtained by round robin test ........................................................... 27

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SIST EN IEC 61788-23:2018
– 4 – IEC 61788-23:2018 © IEC 2018
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SUPERCONDUCTIVITY –
Part 23: Residual resistance ratio measurement –
Residual resistance ratio of Nb superconductors
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international

co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and in

addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,

Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their

preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with

may participate in this preparatory work. International, governmental and non-governmental organizations liaising

with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for

Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.

2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

consensus of opinion on the relevant subjects since each technical committee has representation from all

interested IEC National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

misinterpretation by any end user.

4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

transparently to the maximum extent possible in their national and regional publications. Any divergence between

any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.

5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

services carried out by independent certification bodies.

6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

members of its technical committees and IEC National Committees for any personal injury, property damage or

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and expenses

arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC Publications.

8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent

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

International Standard IEC 61788-23 has been prepared by IEC technical committee 90:

Superconductivity.
The text of this International Standard is based on the following documents:
FDIS Report on voting
90/400/FDIS 90/403/RVD

Full information on the voting for the approval of this International Standard can be found in the

report on voting indicated in the above table.

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

A list of all parts in the IEC 61788 series, published under the general title Superconductivity,

can be found on the IEC website.
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SIST EN IEC 61788-23:2018
IEC 61788-23:2018 © IEC 2018 – 5 –

The committee has decided that the contents of this document 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 document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

IMPORTANT – The 'color inside' logo on the cover page of this publication indicates that

it contains colors which are considered to be useful for the correct understanding of its

contents. Users should therefore print this document using a color printer.
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SIST EN IEC 61788-23:2018
– 6 – IEC 61788-23:2018 © IEC 2018
INTRODUCTION

High-purity niobium is the chief material used to make superconducting radio-frequency cavities.

Similar grades of niobium may be used in the manufacture of superconducting wire.

Procurement of raw materials and quality assurance of delivered products often use the residual

resistance ratio (RRR) to specify or assess the purity of a metal. RRR is defined for

non-superconducting metals as the ratio of electrical resistance measured at room temperature

(293 K) to the resistance measured for the same specimen at low temperature (~4,2 K). The

low-temperature value is often called the residual resistance. Higher purity is associated with

higher values of RRR.

Niobium presents special problems due to its transformation to a superconducting state at ~9 K,

so DC electrical resistance is effectively zero below this temperature. The definition above

would then yield an infinite value for RRR. This document describes a test method to determine

the residual resistance value by using a plot of the resistance to temperature as the test

specimen is gradually warmed through the superconducting transition in the absence of an

applied magnetic field. This results in a determination of the residual resistance at just above

superconducting transition, ~10 K, from which RRR is subsequently determined.

International standards also exist to determine the residual resistance ratio of superconducting

wires. In contrast to superconducting wires, which are usually a composite of a superconducting

material and a non-superconducting material and the RRR value is representative of only the

non-superconducting component, here the entire specimen is composed of superconducting

niobium. Frequently, niobium is procured as a sheet, bar, tube, or rod, and not as a wire. For

such forms, test specimens will likely be a few millimeters in the dimensions transverse to

electric current flow. This difference is significant when making electrical resistance

measurements, since niobium samples will likely be much longer than that for the same

length-to-diameter ratio as a wire, and higher electrical current may be required to produce

sufficient voltage signals. Guidance for sample dimensions and electrical connections is

provided in Annex A. Test apparatus should also take into consideration aspects such as the

orientation of a test specimen relative to the liquid helium surface, accessibility through ports on

common liquid helium dewars, design of current contacts, and minimization of thermal gradients

over long specimen lengths. These aspects distinguish the present document from similar wire

standards.

Other test methods have been used to determine RRR. Some methods use a measurement at a

temperature other than 293 K for the high resistance value. Some methods use extrapolations at

4,2 K in the absence of an applied magnetic field for the low resistance value. Other methods

use an applied magnetic field to suppress superconductivity at 4,2 K. A comparison between this

document and some other test methods is presented in Annex A. It should be noted that

systematic differences of up to 10 % are produced by these other methods, which is larger than

the target uncertainty of this document. Care should therefore be taken to apply this document

or the appropriate corrections listed in Annex A according to the test method used.

Whenever possible, this test method should be transferred to vendors and collaborators who

also perform RRR measurements. To promote consistency, the results of inter-laboratory

comparisons are described in Annex C.
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SIST EN IEC 61788-23:2018
IEC 61788-23:2018 © IEC 2018 – 7 –
SUPERCONDUCTIVITY –
Part 23: Residual resistance ratio measurement –
Residual resistance ratio of Nb superconductors
1 Scope

This part of IEC 61788 addresses a test method for the determination of the residual resistance

ratio (RRR), r , of cavity-grade niobium. This method is intended for high-purity niobium

RRR

grades with 15 < r < 600. The test method should be valid for specimens with rectangular or

RRR
2 2

round cross-section, cross-sectional area greater than 1 mm but less than 20 mm , and a

length not less than 10 nor more than 25 times the width or diameter.
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.

IEC 60050-815, International Electrotechnical Vocabulary – Part 815: Superconductivity

(available at: www.electropedia.org)
3 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 60050-815 and the

following apply.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
residual resistance ratio
RRR

ratio of resistance at room temperature to the resistance just above the superconducting

transition
(1)
r = R / R
RRR 1 2

where is the resistance at 293 K and is the resistance just above the superconducting

R R
1 2
transition, at ~10 K.
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SIST EN IEC 61788-23:2018
– 8 – IEC 61788-23:2018 © IEC 2018
(b)
(a)
T *
Temperature
IEC
Figure 1 – Relationship between temperature and resistance near
the superconducting transition

Note 1 to entry: In this document, the room temperature is defined as 20 °C = 293 K, and is obtained as follows:

RRR

Figure 1 shows schematically resistance versus temperature data and the graphical procedure used to determine the

value of R . In this figure, the region of maximum slope is extrapolated upward in resistance, as shown by line (a),

and the region of minimum slope at temperatures above the transition temperature is extrapolated downward in

temperature, as shown by line (b). The intersection of these extrapolations at point A determines the value of R as

well as a temperature value T .

Note 2 to entry: The value T is similar to the transition value defined in [1] , and should not be confused with the

value defined at the midpoint of the transition, called in [2].

Note 3 to entry: Some standards or documented techniques, e.g. [3][4][5], define with the value of

r R
RRR 1

determined at a temperature other than 293 K, or the value of R determined at a temperature below the

superconducting transition. The user of this document should be alert for such differences in definition.

Note 4 to entry: This note applies to the French language only.
4 Principle

The 4-point DC electrical resistance technique shall be performed both at room temperature and

at cryogenic temperature. The test may be done either as a function of temperature or as a

function of time with increasing temperature.

The relative combined standard uncertainty of this method is 3 % with coverage factor 2.

Measurements shall have the following attributes:

a) Measuring current is sufficiently high to provide voltage signals of the order of 1 µV. For

electrical safety, maximum current density should never exceed 1 A mm .
___________
Numbers in square brackets refer to the Bibliography.
Resistance
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SIST EN IEC 61788-23:2018
IEC 61788-23:2018 © IEC 2018 – 9 –

b) Contact resistance for current leads is sufficiently low to avoid excessive heating of the

sample. Typical cryogenic measurement conditions require power dissipation at contacts to

be less than 1 mW.

c) Sample sizes shall be sufficiently large to minimize effects from cutting and handling

damage. Typical samples are 1 mm to 3 mm in cross-section dimension and > 5 mm in

cross-sectional area.

d) Sample length shall be at least 10 times and not more than 25 times the width or diameter.

Annex A discusses considerations for sample dimensions and measuring current.
5 Measurement apparatus
5.1 Mandrel or base plate

A straight mandrel or base plate shall be used to support the specimen. Possible materials of

construction include pure copper, pure aluminum, pure silver, electrical grades of Cu-Zr,

Cu-Cr-Zr, Cu-Be, and other copper alloys, electrical grades of Al-Mg, Al-Ag, and other aluminum

alloys, and electrical grades of silver alloys. These provide high thermal conductivity and serve

to remove thermal gradients during measurement. Care should be taken to insulate the

specimen from the mandrel. Possible insulating materials include polyethylene terephthalate,

polyester, and polytetrafluoroethylene, which may be applied as foils, tapes, or coatings.

Glass-fiber reinforced epoxy or other composite materials with good thermal conductivity at

cryogenic temperature may also be used.

The base plate should have a clean and smooth surface finish. There should be no burrs, ridges,

seams, or other asperities that may affect the specimen. High purity niobium specimens are soft

and are susceptible to indentation by surface flaws, and such indentations may alter the sample

and invalidate the resistance measurement.

The mandrel or base plate shall support the entire length and width of the specimen. Mandrel or

base plate geometry should not impose a bending strain of more than 0,2 % on the sample.

A thermometer accurate to 0,1 K is helpful but not required. The mandrel or base plate may

incorporate a mounting for a cryogenic thermometer directly against the body of the mandrel or

base plate and near the center of the test specimen.

Practical base plates are at least 30 mm in length to accommodate assembly of pieces and

handling of samples by human hands. Multiple samples may be mounted against a single base

plate.
5.2 Cryostat and support of mandrel or base plate

The apparatus shall make provisions for mechanical support of the mandrel or base plate. In

addition, such support shall provide electrical leads to carry currents for samples and

thermometers, and measure their voltages. For R and R measurements, the support shall

1 2

permit current to flow through only the sample, so that the entire resulting voltage measured is

only that generated by the sample.

The support structure shall permit measurement of both R and R without dismounting or

1 2

remounting the test specimen. Measurement of R shall require the use of a cryostat, which

shall, moreover, integrate with the support.
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SIST EN IEC 61788-23:2018
– 10 – IEC 61788-23:2018 © IEC 2018

The cryostat shall include a liquid helium reservoir at the bottom of a substantial vertical column.

A support structure shall ac
...

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