Electrical accessories - Harmonization of general rules

This technical report provides recommendations and test requirements applicable to electrical accessories. It aims to harmonize general rules for the preparation of international standards in this field.  It gives to that effect recommendations which are intended to be used as a guide.

Petit appareillage - Harmonisation des règles générales

Ce rapport technique donne des recommandations et prescriptions d'essai applicables au petit appareillage électrique. Son but est l'harmonisation des règles générales sur l'élaboration des normes internationales dans ce domaine. Il émet dans ce sens des recommandations qui serviront de guide.

Electrical accessories - Harmonization of general rules

General Information

Status
Published
Publication Date
31-Mar-1999
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
01-Apr-1999
Due Date
01-Apr-1999
Completion Date
01-Apr-1999

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IEC 62884-3
Edition 1.0 2018-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Measurement techniques of piezoelectric, dielectric and electrostatic
oscillators –
Part 3: Frequency aging test methods
Techniques de mesure des oscillateurs piézoélectriques, diélectriques et
électrostatiques –
Partie 3: Méthodes d’essai du vieillissement en fréquence
IEC 62884-3:2018-03(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 62884-3
Edition 1.0 2018-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Measurement techniques of piezoelectric, dielectric and electrostatic
oscillators –
Part 3: Frequency aging test methods
Techniques de mesure des oscillateurs piézoélectriques, diélectriques et
électrostatiques –
Partie 3: Méthodes d’essai du vieillissement en fréquence
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 31.140 ISBN 978-2-8322-6207-8

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
---------------------- Page: 3 ----------------------
– 2 – IEC 62884-3:2018 © IEC 2018
CONTENTS

FOREWORD ........................................................................................................................... 3

INTRODUCTION ..................................................................................................................... 5

1 Scope .............................................................................................................................. 6

2 Normative references ...................................................................................................... 6

3 Terms and definitions, units and symbols ........................................................................ 6

3.1 Terms and definitions .............................................................................................. 6

3.2 Units and symbols................................................................................................... 7

4 Frequency aging test ....................................................................................................... 7

4.1 General ................................................................................................................... 7

4.2 Test and measurement conditions ........................................................................... 7

4.2.1 General ........................................................................................................... 7

4.2.2 Active aging test (non-destructive) ................................................................... 7

4.2.3 Data fitting ....................................................................................................... 8

4.2.4 Accelerated aging (non-active) ........................................................................ 9

4.2.5 Extended aging .............................................................................................. 10

Annex A (normative) Experimental verification of the frequency aging performance ............. 11

Bibliography .......................................................................................................................... 13

Table 1 – Measurement parameters depending on the oscillator type ..................................... 8

Table 2 – Time acceleration factors for E = 0,38 eV ............................................................ 10

Table A.1 – Procedure for the determination of the frequency aging parameters ................... 12

---------------------- Page: 4 ----------------------
IEC 62884-3:2018 © IEC 2018 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MEASUREMENT TECHNIQUES OF PIEZOELECTRIC,
DIELECTRIC AND ELECTROSTATIC OSCILLATORS –
Part 3: Frequency aging test methods
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

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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 62884-3 has been prepared by IEC technical committee 49:

Piezoelectric, dielectric and electrostatic devices and associated materials for frequency

control, selection and detection.

This bilingual version (2018-11) corresponds to the monolingual English version, published in

2018-03.
The text of this International Standard is based on the following documents:
CDV Report on voting
49/1248/CDV 49/1272/RVC

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.
---------------------- Page: 5 ----------------------
– 4 – IEC 62884-3:2018 © IEC 2018
The French version of this standard has not been voted upon.

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

A list of all parts in the IEC 62884 series, published under the general title Measurement

techniques of piezoelectric, dielectric and electrostatic oscillators, can be found on the IEC

website.

The committee has decided that the contents of this document will remain unchanged until the

stability date indicated on the IEC website 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.
---------------------- Page: 6 ----------------------
IEC 62884-3:2018 © IEC 2018 – 5 –
INTRODUCTION

This document was developed from the works related to IEC 60679-1:2007 (third edition), the

measurement techniques of which were restructured into different parts under a new project

reference. This document describes the measurement method for frequency aging only.

---------------------- Page: 7 ----------------------
– 6 – IEC 62884-3:2018 © IEC 2018
MEASUREMENT TECHNIQUES OF PIEZOELECTRIC,
DIELECTRIC AND ELECTROSTATIC OSCILLATORS –
Part 3: Frequency aging test methods
1 Scope

This part of IEC 62884 describes the methods for the measurement and evaluation of

frequency aging tests of piezoelectric, dielectric and electrostatic oscillators, including

Dielectric Resonator Oscillators (DRO) and oscillators using FBAR (hereinafter referred to as

"Oscillator"). The purpose of those tests is to provide statistical data supporting aging

predictions.
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 60027 (all parts), Letter symbols to be used in electrical technology

IEC 60050-561, International electrotechnical vocabulary – Part 561: Piezoelectric, dielectric

and electrostatic devices and associated materials for frequency control, selection and

detection

IEC 60469, Transitions, pulses and related waveforms – Terms, definitions and algorithms

IEC 60617, Graphical symbols for diagrams, available at http://std.iec.ch/iec60617

IEC 60679-1, Piezoelectric, dielectric and electrostatic oscillators of assessed qualify – Part 1:

Generic specification

IEC 62884-1:2017, Measurement techniques of piezoelectric, dielectric and electrostatic

oscillators – Part 1: Basic methods for the measurement
ISO 80000-1, Quantities and units – Part 1: General
3 Terms and definitions, units and symbols
3.1 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 60679-1 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
---------------------- Page: 8 ----------------------
IEC 62884-3:2018 © IEC 2018 – 7 –
3.2 Units and symbols

Units, graphical symbols, letter symbols and terminology shall, wherever possible, be taken

from the following standards:
• IEC 60027;
• IEC 60050-561;
• IEC 60469;
• IEC 60617;
• ISO 80000-1.
4 Frequency aging test
4.1 General

The test and measurement procedures shall be carried out in accordance with the relevant

detail specification.

Where any discrepancies occur for any reason, documents shall rank in the following order of

precedence:
– detail specification;
– sectional specification;
– generic specification;

– any other international documents (for example of the IEC) to which reference is made.

The same order of precedence shall apply to equivalent national documents.
4.2 Test and measurement conditions
4.2.1 General

General test and measurement conditions refer to IEC 62884-1, and especially the output

frequency measurement to 4.5.4 of IEC 62884-1:2017.
4.2.2 Active aging test (non-destructive)
Purpose: Statistical verification of aging performance.

Unless otherwise specified, the operating oscillator unit shall be maintained at the specified

temperature for a continuous period as given in Annex A.

During the period of test, the control of temperature and the accuracy of frequency

measurement shall be consistent with the accuracy of the maximum frequency variations

specified. The oscillator unit shall remain in the chamber throughout the duration of the test

and shall be continually supplied with input power, unless otherwise specified.

After insertion into the oven, the oscillator shall be allowed to equilibrate with chamber air

temperature. Then the oscillator shall be energized and stabilized prior to beginning of and

during the measurement acquisition cycle.
The stabilization time t depends on the type of oscillator as shown in Table 1.
stab

The initial frequency f of the oscillator shall be measured immediately after the stabilization

init
period t and thereafter at intervals as shown in Table 1.
stab
---------------------- Page: 9 ----------------------
– 8 – IEC 62884-3:2018 © IEC 2018
Table 1 – Measurement parameters depending on the oscillator type

Oscillator type Stabilization Test intervals* Aging temperature Aging temperature

time t * T (°C)* tolerance**
stab oven
SPXO, VCXO 1 h See Annex A See Annex A ± 3 K
TCXO 48 h See Annex A See Annex A ± 3 K
OCXO 48 h See Annex A +25 °C ± 3 K
* unless otherwise specified
** measurement tolerance < ± 0,5 K
The measurement interval should be divided logarithmically.

If the aging test is used for qualification, at least 5 oscillators of identical or structurally similar

type shall be tested.

The frequency change between the initial frequency f and all subsequent frequencies

init

measured within the specified period shall not exceed the maximum frequency change

specified. Measurements shall be carried out according to 4.5.4 of IEC 62884-1:2017.

4.2.3 Data fitting

If a projected total frequency change for a period (such as 365 days (1 year)) is specified, an

extrapolation shall be used from the end of the aging measurement period using the

coefficients determined from a curve fitting to the measurements.

The frequency measurement data f (t) shall be fit using the method of least squares of the

following function (logarithmic fit):
 
∆f (t)
= a + a ⋅ln(a ⋅ t+1)
 
0 1 2
init
 

where ∆f (t) is the frequency difference of the oscillator at t days after the start of the aging

cycle and the initial frequency f measured after the stabilization time t (the time origin

init stab

for measurements analysis shall be the beginning of the stabilization period). The coefficients

a , a and a are constants to be determined from the least squares fit.
0 1 2

For monotonic aging, all the measurements shall be used for the curve fitting. If the aging

trend is not monotonic, the measurement period shall be extended to 40 days or longer after

the extremum in the aging trend, and the measurements from 12 days after the extremum is

reached to the end of the aging measurement period shall be fit to the above function (unless

otherwise specified).

The default fitting algorithm is the logarithmic fit. In some cases, namely when the aging

response has a very small curvature, the logarithmic fit may not yield reasonable results. In

this case the following polynomial fit is recommended to be calculated additionally:

1 1
∆f (t)
2 3
= a + a ⋅t+ a ⋅t + a ⋅t
  0 1 2 3
 init 
---------------------- Page: 10 ----------------------
IEC 62884-3:2018 © IEC 2018 – 9 –

This approach should only be used if the square root of the least square fit variance of the

measurements from the polynomial fit is at least five times smaller than that of the logarithmic

fit.

The total frequency change and the aging rate at the end of the specified aging period (t = T )

shall be determined from the fitting equation using the constants determined from the least

squares fit. The square root of the least squares fit variance of the measurements from the

curve-fit function shall not exceed 5 percent of the total aging change allowed during the test

period.

For the logarithmic fitting (default) the aging rate (in ppm or ppb per day) at t = T is:

 
∆f (t)
d 
 
 
a⋅ a f (T +1)− f (T )
 init 
1 2 a a
 
= ≈
 
dt a ⋅T +1 f
2 a init
 
 
t=T
If the polynomial fitting was used, the aging rate at t = T (T >0) is:
a a
 
 
∆f (t)
 
 
1 2
 
f − −
init
  3
  2
2 3
= a + ⋅T + ⋅T
1 a a
 
dt 2 3
 
 
 
t=Ta

The projected total frequency change for a time period shall be calculated with the following

formulas:
f (T +30)− f (T )
a a
Aging per month ≈
init
f (T +365)− f (T )
a a
Aging per (1 ) year ≈
init
f (T + N⋅365)− f (T )
a a
Aging over N years ≈
init

If polynomial fitting was used inflection of the aging response may occur over time.

If aging after N days operation is specified (for OCXO usually T = 30 days), in the above

op op
formulae T should be replaced by (T + N ).
a a op
4.2.4 Accelerated aging (non-active)

For special applications, it is possible to accelerate the aging of SPXO, VCXO and TCXO at

higher temperatures, e.g. at +85 °C, +105 °C or +125 °C. This temperature has to be lower or

equal to the specified maximum storage temperature.

The ratio between the storage time at +25 °C and the storage time at an elevated temperature

T to achieve the same amount of frequency aging is called time acceleration factor TAF.

oven
---------------------- Page: 11 ----------------------
– 10 – IEC 62884-3:2018 © IEC 2018

This factor depends on the design of the used crystal unit and on the production process. It

can be determined experimentally as described in Annex A, or taken from experience with

structurally similar oscillators, or can be mutually agreed between manufacturer and user.

If the time acceleration factor TAF is not otherwise specified, the following approach is

recommended:

Applying Arrhenius’ law, the acceleration factor TAF is related to the activation energy E by

the following equation:
 
1 1
 
E ⋅ −
 
T T
ref oven
 
TAF= e

with k = Boltzmann’s constant (k ≈ 8,617·10 eV/K), and the temperatures given in K.

The activation energy E is decreasing over time, i.e. the acceleration factor becomes lower

with the aging time. Furthermore, E varies between the different crystals and oscillators,

depending on frequency, package size, resonator design and production processes. The

observed values of E were between > 0,1 eV and < 1 eV.

For example, a common assumption is TAF = 12 for T = +85 °C, i.e. 30 days (1 month)

oven

aging at 85 °C are considered to be equivalent to 365 days (12 months) aging at +25 °C,

which corresponds to an activation energy E of 0,38 eV.

With this value of E the time acceleration factor for other aging temperatures can be

calculated. Table 2 below shows the time acceleration factor TAF and the number of days N

for to equivalent of 365 days at +25 °C.
Table 2 – Time acceleration factors for E = 0,38 eV
T (°C) TAF N (days)
oven d
+25 1 365
+85 12 30
+105 23 16
+125 41 9

NOTE Other time acceleration factors can be agreed between manufacturer and user based on their own

reliability calculations.
4.2.5 Extended aging
Purpose: Evaluation of reliability and long-term performance.

This test shall be carried out in accordance with 4.2.1, except that the continuous periods

shall be 1 000 h, 2 000 h or 8 000 h, as prescribed in the detail specification. Measurements

shall be carried out according to 4.5.4 of IEC 62884-1:2017, except that they should be made

at (25 ± 2) °C or any other specified temperature. The measurement intervals can be

extended to 2 weeks or longer. For the intermediate and the final measurements, the

oscillator can be removed from the oven, and stored at room temperature for 1 hour. Thermal

shocks should be avoided. The frequency measurement shall be performed at a reference

temperature of (25 ± 2) °C.
This test shall be used for information purposes only.
---------------------- Page: 12 ----------------------
IEC 62884-3:2018 © IEC 2018 – 11 –
Annex A
(normative)
Experimental verification of the frequency aging performance
Assumption:
Frequency aging can generally be expressed as
(t,T)= g(t)⋅ h(T)
where
is the relative frequency change due to aging;
t is the time, usually in days;
T is the temperature in K;
g(t) describes the time dependence of the frequency aging;
h(T) describes the temperature dependence of the frequency aging,
and with:
g(t)= b + b⋅log(b ⋅t+1) (logarithmic fit)
0 1 2
1 1
2 3
g(t)= c + c ⋅t+ c ⋅t + c ⋅t (polynomial fit)
0 1 2 3
and
 
 
1 1
 
 
E ⋅ −
 
 T T 
ref
 
h(T)= a⋅exp
 
 
 
 

with k = Boltzmann’s constant (k ≈ 8.617·10 eV/K), and the temperatures given in k, where

T = 298 K.
ref

The fitting parameters b , b , b (and/or c , c , c , c ) and a , and E are determined by the

0 1 2 0 1 2 3 1 a
procedure indicated in Table A.1:
---------------------- Page: 13 ----------------------
– 12 – IEC 62884-3:2018 © IEC 2018
Table A.1 – Procedure for the determination of the frequency aging parameters
Procedure SPXO, VCXO, TCXO OCXO, high-stability TCXO, and
high-reliability oscillators
Aging test procedure passive active

Reflow Solder test 2x ROHS-profile (IEC 61760-1)* 2x RoHS -profile (IEC 61760-1)* if

applicable
Initial pre-aging 48 hours at > 20K above upper OCXO: 48 hours active aging.

(time and temperature) operating temperature, but T Others: 48 hours at > 20K above

< upper storage temperature upper operating temperature, but T
≤ upper operable temperature
Sample size per lot ≥ 30* OCXO: ≥ 5*
(from one production lot) depending on needed confidence Others: 10*
depending on needed confidence
level
level
Number of aging temperatures 3 OCXO: 1
Others: 3
Recommended aging +85 °C, +105 °C, +125 °C, +150 °C* OCXO: +25 °C
temperatures depending on application, Others: +85 °C, +105 °C, +125 °C*
T < specified upper storage depending on application,
temperature T < specified upper operating
temperature
Recommend temperature for (+25 ± 1) °C, OCXO: (+25±3) °C
measurement measurement > 1 hour after removal Others: (+25±1) °C, measurement
from temperature chamber. > 1 hour after removal from
temperature chamber. Avoid thermal
Avoid thermal shocks
shocks
Recommended aging time 500, 1 000, 2 000* hours OCXO: 30 days
depending on needed confidence Others: 500, 1 000, 2 000* hours
level depending on needed confidence
level
Test intervals After 48 h stabilization: OCXO: After 48 h stabilization:

(in “logarithmic” steps) 24 h, 72 h, 250 h, 500 h, 750 h, minimum 4 times per week (7 days)

1 000 h(, 1 500 h, 2 000 h) at intervals of at least 20 hours
Others: After 48 h stabilization:
24 h, 72 h, 250 h, 500 h, 750 h,
1 000 h, (1 500 h, 2 000h)
Algorithms to determine g(t) and Least square fitting** Least square fitting**
h(T) g(t): log fit and polynomial fit, g(t): log fit and polynomial fit,
Polynomial fit – only if Polynomial fit – only if sum of least
sum of least squares (SLQ) squares (SLQ)< 5 times SLQ of
< 5 times SLQ of Logarithmic fit Logarithmic fit
h(T): least square fitting h(T): least square fitting
Result: E Result: E
a a
E may vary with time. E may vary with time.
a a
Use E for t ≥ 500h Use E for t ≥ 500 h
a a
* Unless otherwise specified

** For monotonic aging, all measurements shall be used for the curve fitting. If the aging trend is not

monotonic, the measurement period shall be extended up to 40 days or longer after the extremum in the

aging trend, and the measurements form 12 days after the extremum is reached to the end of the aging

measurement period shall be fit to the above functions for g(t).
---------------------- Page: 14 ----------------------
IEC 62884-3:2018 © IEC 2018 – 13 –
Bibliography
IEC 60068-1, Environmental testing – Part 1: General and guidance
IEC 60068-2-14, Environmental testing – Part 2-14: Tests – Tes
...

SLOVENSKI STANDARD
SIST IEC/TR 61916:1999
01-april-1999
Electrical accessories - Harmonization of general rules
Electrical accessories - Harmonization of general rules
Petit appareillage - Harmonisation des règles générales
Ta slovenski standard je istoveten z: IEC/TR 61916
ICS:
29.120.01 (OHNWULþQDGRGDWQDRSUHPD Electrical accessories in
QDVSORãQR general
SIST IEC/TR 61916:1999 en

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

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SIST IEC/TR 61916:1999
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SIST IEC/TR 61916:1999
RAPPORT
CEI
TECHNIQUE – TYPE 3
IEC
61916
TECHNICAL
Première édition
REPORT – TYPE 3
First edition
1998-09
Petit appareillage –
Harmonisation des règles générales
Electrical accessories –
Harmonization of general rules
 IEC 1998 Droits de reproduction réservés  Copyright - all rights reserved

Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in

utilisée sous quelque forme que ce soit et par aucun any form or by any means, electronic or mechanical,

procédé, électronique ou mécanique, y compris la photo- including photocopying and microfilm, without permission in

copie et les microfilms, sans l'accord écrit de l'éditeur. writing from the publisher.

International Electrotechnical Commission 3, rue de Varembé Geneva, Switzerland
Telefax: +41 22 919 0300 e-mail: inmail@iec.ch IEC web site http: //www.iec.ch
CODE PRIX
Commission Electrotechnique Internationale
PRICE CODE U
International Electrotechnical Commission
Pour prix, voir catalogue en vigueur
For price, see current catalogue
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SIST IEC/TR 61916:1999
61916/TR © IEC:1998 – 3 –
CONTENTS
Page

FOREWORD ................................................................................................................... 7

INTRODUCTION ............................................................................................................. 9

Clause

1 General.................................................................................................................... 11

1.1 Scope.............................................................................................................. 11

1.2 Reference documents...................................................................................... 11

2 Resistance to heat .................................................................................................... 13

2.1 Requirements.................................................................................................. 13

2.2 Tests............................................................................................................... 13

3 Screws, current carrying parts and connections (electrical and mechanical)............... 17

3.1 Definitions....................................................................................................... 19

3.1.1 Tapping for thread-forming screw....................................................... 19

3.1.2 Tapping for thread-cutting screw ........................................................ 19

3.2 Requirements.................................................................................................. 21

3.3 Tests............................................................................................................... 25

4 Resistance to abnormal heat and to fire .................................................................... 27

4.1 Requirements.................................................................................................. 27

4.2 Tests............................................................................................................... 29

4.2.1 Object of the test ............................................................................... 29

4.2.2 General description of the test............................................................ 29

4.2.3 Description of test apparatus.............................................................. 29

4.2.4 Degree of severity.............................................................................. 31

4.2.5 Calibration of the thermocouple.......................................................... 33

4.2.6 Preconditioning.................................................................................. 33

4.2.7 Initial measurements.......................................................................... 33

4.2.8 Test procedure................................................................................... 33

4.2.9 Observations and measurements ....................................................... 35

4.2.10 Evaluation of test results .................................................................... 35

4.2.11 Information to be given in the relevant specification............................ 35

5 Resistance of insulating materials to tracking ............................................................ 39

5.1 Definitions....................................................................................................... 41

5.1.1 Tracking............................................................................................ 41

5.1.2 Electrical erosion............................................................................... 41

5.1.3 Comparative tracking index (CTI) ....................................................... 41

5.1.4 Proof tracking index (PTI) .................................................................. 41

5.2 Requirements.................................................................................................. 41

5.3 Tests............................................................................................................... 41

5.3.1 Test specimens.................................................................................. 41

5.3.2 Conditioning....................................................................................... 43

5.3.3 Test apparatus................................................................................... 43

5.3.4 Procedure.......................................................................................... 45

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SIST IEC/TR 61916:1999
61916/TR © IEC:1998 – 5 –
Clause Page

6 Resistance to rusting ................................................................................................ 51

6.1 Requirements.................................................................................................. 51

6.2 Test................................................................................................................. 51

7 Legibility, durability and indelibility of marking ........................................................... 51

7.1 Requirements.................................................................................................. 53

7.2 Test................................................................................................................. 53

8 Screw-type terminals for connecting conductors ........................................................ 53

9 Criteria for tests in accessory standards.................................................................... 53

10 Tolerances............................................................................................................... 55

11 Mechanical strength – Free fall ................................................................................. 55

11.1 Requirements.................................................................................................. 55

11.2 Tests............................................................................................................... 55

Figure 2.1 – Ball pressure test apparatus ......................................................................... 15

Figure 2.2 – Jointed test finger ........................................................................................ 17

Figure 3.1 – Thread-forming screw .................................................................................. 19

Figure 3.2 – Thread-cutting screw.................................................................................... 19

Figure 4.1 – Glow-wire and position of the thermocouple.................................................. 37

Figure 4.2 – Test apparatus (example)............................................................................. 39

Figure 5.1 – Electrode ..................................................................................................... 47

Figure 5.2 – Electrode arrangement ................................................................................. 47

Figure 5.3 – Example of test apparatus............................................................................ 47

Figure 5.4 – Example of test circuit .................................................................................. 49

Table 1 – Torque per thread diameter .............................................................................. 25

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SIST IEC/TR 61916:1999
61916/TR © IEC:1998 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
ELECTRICAL ACCESSORIES –
HARMONIZATION OF GENERAL RULES
FOREWORD

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

all national electrotechnical committees (IEC National Committees). The object of the 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, the IEC publishes International Standards. 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. The 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 the 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 National Committees.

3) The documents produced have the form of recommendations for international use and are published in the form

of standards, technical reports or guides and they are accepted by the National Committees in that sense.

4) In order to promote international unification, IEC National Committees undertake to apply IEC International

Standards transparently to the maximum extent possible in their national and regional standards. Any

divergence between the IEC Standard and the corresponding national or regional standard shall be clearly

indicated in the latter.

5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any

equipment declared to be in conformity with one of its standards.

6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject

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

The main task of the IEC technical committees is to prepare International standards. In

exceptional circumstances, a technical committee may propose the publication of a technical

report of one of the following types:

• type 1, when the required support cannot be obtained for the publication of an International

Standard, despite repeated efforts;

• type 2, when the subject is still under technical development or where for any other reason

there is the future but not immediate possibility of an agreement on an International

Standard;

• type 3, when a technical committee has collected data of a different kind from that which is

normally published as an International Standard, for example "state of the art".

Technical reports of types 1 standards 2 are subject to review within three years of publication

to decide whether they can be transformed into International Standards. Technical reports of

type 3 do not necessarily have to be reviewed until the data they provide are considered to be

no longer valid or useful.

IEC 61916 which is a technical report of type 3 has been prepared by IEC technical committee

23: Electrical accessories.
The text of this technical report is based on the following documents:
Committee draft Report on voting
23/239/CDV 23/245/RVC

Full information on the voting for the approval of this technical report can be found in the report

on voting indicated in the above table.
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SIST IEC/TR 61916:1999
61916/TR © IEC:1998 – 9 –
INTRODUCTION

Many rules in the Standards established by TC 23 and its eight subcommittees are identical.

An harmonization is required as far as principle and redaction are concerned.

During the general meeting of TC 23, held in Stockholm in June 1980 (see PV2341/TC23

item VIII), the question of "General Rules" in TC 23 was discussed. It was decided to create a

Coordinating Group which would have as main task to harmonize the so-called "General

Rules". This work was carried out during the ensuing years by TC 23, following proposals by

the Coordinating Group, during the meetings of Zurich (26 Jan, 1984/RM2661/TC23 item V),

Rome (27/29 Nov, 1985/RM2879/TC23 items VIII and IX), Brussels (9 Apr, 1987/RM3073/TC23

annex AI), Adelaide (28 Oct, 1988/RM3118/TC23 appendix A), Beijing (26 Oct, 1990/

RM3520/TC23 item VII). This document was modified by document 23/239/CDV and approved

after voting (see 23/245/RVC)

The purpose of this work is to gain time and avoid repeating discussions within TC 23 and its

subcommittees and finally, to have harmonized rules on the same subjects in all the Standards

published by TC 23 and its subcommittees.

These recommendations are meant as a guide. Consequently, each subcommittee may use

whole or part of the document which is not meant to be compulsory.

In publishing these recommendations, TC 23 wishes to spread the information so that other

committees of the IEC may use these recommendations, if necessary.
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SIST IEC/TR 61916:1999
61916/TR © IEC:1998 – 11 –
ELECTRICAL ACCESSORIES –
HARMONIZATION OF GENERAL RULES
1 General
1.1 Scope

This technical report provides recommendations and test requirements applicable to electrical

accessories. It aims to harmonize general rules for the preparation of international standards in

this field. It gives to that effect recommendations which are intended to be used as a guide.

1.2 Reference documents

IEC 60051 (all parts), Direct acting indicating analogue electrical measuring instruments and

their accessories

IEC 60068-2-32:1975, Basic environmental testing procedures – Part 2: Tests. Test Ed: Free fall

Amendment 2 (1990)

IEC 60112:1979, Method for determining the comparative and the proof tracking indices of solid

insulating materials under moist conditions
IEC 60228:1978, Conductors of insulated cables
IEC 60584-1:1995, Thermocouples – Part 1: Reference tables

IEC 60669-1:1993, Switches for household and similar fixed-electrical installations – Part 1:

General requirements

IEC 60695-2-1/0:1994, Fire hazard testing – Part 2: Test methods – Section 1/sheet 0: Glow-

wire test methods – General

IEC 60695-2-1/1:1994, Fire hazard testing – Part 2: Test methods – Section 1/sheet 1: Glow-

wire end product test and guidance

IEC 60898:1995, Electrical accessories – Circuit breakers for overcurrent protection for

household and similar installations

IEC 60998-1:1990, Connecting devices for low voltage circuits for household and similar

purposes – Part 1: General requirements

IEC 60998-2-1:1990, Connecting devices for low voltage circuits for household and similar

purposes – Part 2-1: Particular requirements for connecting devices as separate entities with

screw-type clamping units

IEC 60999 (all parts), Connecting devices – Safety requirements for screw-type and screwless-

type clamping units for electrical copper conductors

ISO 1456:1988, Metallic coatings – Electrodeposited coatings of nickel plus chromium and of

copper plus nickel plus chromium

ISO 2081:1986, Metallic coatings – Electroplated coatings of zinc on iron or steel

ISO 2093:1986, Electroplated coatings of tin – Specification and test methods
ISO 4046:1978, Paper, board, pulp and related terms – Vocabulary
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SIST IEC/TR 61916:1999
61916/TR © IEC:1998 – 13 –
2 Resistance to heat

The following guiding document which, after study by the Co-ordinating Group and TC 23 (see

RM2879/TC23 item VIII), was circulated as 23(Sec)143, is applicable to the clauses covering

requirements and tests to determine the resistance to heat of accessories. These

recommendations are in accordance with IEC 60669-1: Switches for household and similar

fixed electrical installations – Part 1: General requirements. 2nd ed.,1993.
The text includes two clauses:
– Requirements (clause 2.1)
– Tests (clause 2.2)
For editing purposes the order and the numbers may be altered if necessary
2.1 Requirements

Accessories including enclosures, if any, shall be sufficiently resistant to heat.

Compliance is checked by the tests of clause 2.2.
2.2 Tests
Verification of resistance to heat

a) for accessories, with the exception of the parts, if any, covered by items b) and c), by the

tests of 2.2.1, 2.2.2 and 2.2.4

b) for boxes, separable covers and cover plates, by the test of 2.2.2. This test is unnecessary

if there is an ageing test.

c) for accessories having an enclosure made of natural or synthetic rubber or a mixture of

both, by the test of 2.2.4

2.2.1 The specimens are kept for 1 h in a heating cabinet at a temperature of (100 ± 2) °C.

During the test, they shall not undergo any change impairing their further use, and sealing

compound, if any, shall not flow to such an extent that live parts are exposed.

After the test, the specimens are allowed to cool down to approximately room temperature.

When the standard finger, as shown in figure 2.1, is applied with a force not exceeding 5 N,

there shall be no access to live parts when the accessories are mounted as for normal use.

After the test, marking shall still be legible.

Discolouration, blisters or slight displacements of the sealing compound are disregarded

provided that safety is not impaired.

2.2.2 The specimens are submitted to a test, which is identical to the one described in 2.2.1,

the only difference being that the specimens are kept for 1 h in a heating cabinet at a

temperature of (70 ± 2) °C.
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SIST IEC/TR 61916:1999
61916/TR © IEC:1998 – 15 –

2.2.3 Parts of insulating material necessary to retain current-carrying parts and parts of the

earthing circuit in position are subjected to a ball-pressure test by means of the apparatus

shown in figure 2.1, except that insulating parts to retain the earthing terminals on a box shall

be tested as specified in 2.2.4.

Before the test is started, the ball and the support on which the specimen shall be placed, are

brought to the temperature specified. The part under test shall be placed on a 3 mm thick steel

plate in direct contact with it, so as to be supported to withstand the test force.

NOTE – When it is not possible to carry out the test on the specimens, the test should be carried out on a piece at

least 2 mm thick which is cut out of the specimen. If this is not possible, up to and including four layers, each cut

out of the same specimen, may be used, in which case the total thickness of the layers should be not less than

2,5 mm.

The surface of the part to be tested is placed in the horizontal position and a steel ball of 5 mm

diameter is pressed against the surface with a force of 20 N.

The test lead and the supporting means shall be placed within the heating cabinet for a

sufficient time to ensure that they have attained the stabilized testing temperature before the

test commences.
The test is made in a heating cabinet at a temperature of (125 ± 2) °C.

After 1 h, the ball is removed from the specimen which is then cooled down within 10 s to

approximately room temperature by immersion in cold water.

The diameter of the impression caused by the ball is measured and shall not exceed 2 mm.

2.2.4 Parts of insulating materials not necessary to retain current-carrying parts and parts of

the earthing circuit in position, even though they are in contact with them, are subjected to a

ball-pressure test in accordance with 1.2.3, but the test is made at a temperature of

(75 ± 2) °C, or (40 ± 2) °C plus the highest temperature rises determined for the relevant part

during the test of clause "Temperature rise test", whichever is the higher.
Figure 2.1 – Ball-pressure test apparatus
This figure is extracted from IEC 60695-10-2, 1st ed. 1995-08, p. 10.
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SIST IEC/TR 61916:1999
61916/TR © IEC:1998 – 17 –
Material: metal, except where otherwise specified
Linear dimensions in millimetres
Tolerances on dimensions without specific tolerance:
on angles
on linear dimensions: up to 25 mm:
−00, 5
over 25 mm: ±0,2

Both joints shall permit movement in the same plane and the same direction through an angle

of 90° with a 0° to +10° tolerance.
Dimensions in millimetres
Figure 2.2 – Jointed test finger
This figure is extracted from IEC 60529, 2nd ed., 1989-11, p. 58.
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SIST IEC/TR 61916:1999
61916/TR © IEC:1998 – 19 –
3 Screws, current carrying parts and connections (electrical and mechanical)

The following guiding document, which after study by the Coordinating Group and TC 23 (see

RM2879/TC23 item VIII), was circulated as 23(Sec)144, is applicable to the clauses covering

the requirements and tests of screws, current carrying part and connections (electrical and

mechanical) of accessories. These recommendations are in accordance with IEC 60669-1:

Switches for household and similar fixed-electrical installations – Part 1: General requirements,

and IEC 60898: Circuit breakers for overcurrent protection of household and similar

installations, 2nd ed. 1995.
The text includes three clauses as follows:
– Definitions (clause 3.1)
– Requirements (clause 3.2)
– Tests (clause 3.3)
For editing purposes, the order and numbers may be altered, if necessary.
3.1 Definitions
3.1.1 Tapping for thread-forming screw

A tapping screw having an uninterrupted thread which by screwing-in forms a thread by

displacing material in the cavity.
An example of a thread-forming screw is shown in figure 3.1.
Figure 3.1 – Thread-forming screw
3.1.2 Tapping for thread-cutting screw

A screw having an interrupted thread which, by screwing-in, makes a thread by removing

material from the cavity.
An example of thread-cutting screw is shown in figure 3.2.
Figure 3.2 – Thread-cutting screw
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SIST IEC/TR 61916:1999
61916/TR © IEC:1998 – 21 –
3.2 Requirements

3.2.1 Connections, electrical or mechanical, using screws and nuts, shall withstand the

mechanical stresses occurring in normal use.

Screws and nuts which transmit contact pressure and which are operated when connecting and

mounting an accessory during installation, and/or which are likely to be operated during the life

of the accessory, shall be in engagement with a metal thread.
Screws for connecting external conductors shall not be tapping screws.

Screws and nuts operated when mounting the accessory during installation, and/or which are

likely to be operated during the life of the accessory, shall not be of the thread cutting type.

NOTE – Screws and nuts which are operated when mounting the accessory include screws for fixing cover of cover

plates, etc., but not connecting means for screwed conduits and screws for fixing the base of the accessory.

Compliance is checked by inspection and by the test of clause 3.3.

NOTE – Attention is drawn to the fact that screwed connections also have to comply with the requirements

applicable to the accessory.

3.2.2 For screws in engagement with a thread of insulating material and screws of insulating

material, which are used for the installation of the accessory and/or which are likely to be

operated during the life of the accessory, correct introduction of the screw into the screw hole

or nut shall be ensured.

Screws of insulating materials shall not be used in cases when the replacement with metal

screws could impair the insulation of the accessory.
Compliance is checked by inspection and by manual test.

NOTE – The requirements with regard to correct introduction are met if introduction of the screw in a slanting

manner is prevented, for example by guiding the screw by the part to be fixed, by a recess in the female thread or

by the use of a screw with the leading thread removed.

3.2.3 Screws and rivets, which serve as electrical as well as mechanical connections, shall be

locked against loosening or turning.
Compliance is checked by inspection and manual test.

NOTE – Spring washers may provide satisfactory locking. For rivets, a non-circular shank or an appropriate notch

may be sufficient. Sealing compound which softens on heating provides satisfactory locking only for screw

connections not subjected to torsion in normal use.

3.2.4 Electrical connections shall be so designed that contact pressure is not transmitted

through insulating material other than ceramic, pure mica or other material with characteristics

no less suitable, unless there is sufficient resiliency in the metallic parts to compensate for any

possible shrinkage or yielding of the insulating material.
Compliance is checked by inspection.

NOTE – The suitability of the material is considered as regards the stability of the dimensions.

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SIST IEC/TR 61916:1999
61916/TR © IEC:1998 – 23 –

3.2.5 Current-carrying parts, including those of terminals (also earthing terminals), shall be of

a metal having, under the conditions occurring in the equipment, mechanical strength,

electrical conductivity and resistance to corrosion adequate for their intended use.

Compliance is checked by inspection and, if necessary, by chemical analysis.

Examples of suitable metals, when used within a permissible temperature range and under

normal conditions of chemical pollution are:
– copper;

– an alloy containing at least 58 % copper for part that are worked cold or at-least 50 %

copper for other parts;

– stainless steel containing at least 13 % chromium and not more than 0,09 % carbon;

– steel provided with an electroplated coating of zinc according to ISO 2081, the coating

having a thickness of at least:
• 5 μ (ISO service condition 1) for ordinary equipment
• 8 μ (ISO service condition 2) for drip-proof and splash-proof equipment
• 12 μ (ISO service condition 3) for jet-proof and watertight equipment;

– steel provided with an electroplated coating of nickel and chromium according to ISO 1456,

the coating having a thickness of at least:
• 10 μm (ISO service condition 1) for ordinary equipment
• 20 μm (ISO service condition 2) for drip-proof and splash-proof equipment
• 30 μm (ISO service condition 3) for jet-proof and watertight equipment;

– steel provided with an electroplated coating of tin, according to ISO 2093, the coating

having a thickness equal to at least that specified for:
• 12 μ (ISO service condition 1) for ordinary equipment
• 20 μ (ISO service condition 2) for drip-proof and splash-proof equipment
• 30 μ (ISO service condition 3) for jet-proof and watertight equipment

Parts which may be subjected to mechanical wear, shall not be made of steel provided with

an electroplated coating;

– steel provided with an electroplated coating of zinc is only permitted for prime current-

carrying parts if no fixed connection is intended to be made. For connection, an

electroplated coating of zinc is permissible only on parts which do not participate directly in

current transmission, such as screws or washers used for certain types of terminals in

which they transmit only the contact pressure.

NOTE 1 – This requirement is not intended to apply to contacts, magnetic circuits, heating elements, bimetallic

components, shunts, parts of electronic devices, etc.

NOTE 2 – Screws, nuts, washers, clamping plates and similar parts of terminals are not regarded as current-

carrying parts.

NOTE 3 – New requirements to be verified by a test for determining the resistance to corrosion are under

consideration. These requirements should permit other materials to be used if suitably coated.

Under moist conditions, metals having a great difference of electrochemical potential with

respect to each other, shall not be used in contact with each other.
Compliance is checked by inspection.
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SIST IEC/TR 61916:1999
61916/TR © IEC:1998 – 25 –

3.2.6 Thread-forming screws and thread-cutting screws shall not be used for the connection

of current-carrying parts. Thread-forming screws and thread cutting screws may be used to

provide earthing continuity, provided that it is not necessary to disturb the connection in normal

use and at least two screws are used for each connection.
Compliance is checked by inspection.

NOTE – The use of thread-forming screws without displacing of material which are operated when mounting the

switch are under consideration.
3.3 Tests

Compliance with the requirements of 3.2.1 is checked by inspection and by the foll

...

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