IEC 60393-2:2015

IEC 60393-2 ®
Edition 3.0 2015-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Potentiometers for use in electronic equipment –
Part 2: Sectional specification – Lead-screw actuated and rotary preset
potentiometers
Potentiomètres utilisés dans les équipements électroniques –
Partie 2: Spécification intermédiaire – Potentiomètres d'ajustement multitours et
rotatifs
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IEC 60393-2 ®
Edition 3.0 2015-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Potentiometers for use in electronic equipment –

Part 2: Sectional specification – Lead-screw actuated and rotary preset

potentiometers
Potentiomètres utilisés dans les équipements électroniques –

Partie 2: Spécification intermédiaire – Potentiomètres d'ajustement multitours et

rotatifs
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 31.040.20 ISBN 978-2-8322-3060-2

– 2 – IEC 60393-2:2015  IEC 2015
CONTENTS
FOREWORD . 4
1 General . 6
1.1 Scope . 6
1.2 Normative references . 6
1.3 Information to be given in a detail specification . 6
1.3.1 General . 6
1.3.2 Outline drawing and dimensions . 7
1.3.3 Mounting . 7
1.3.4 Style . 7
1.3.5 Resistance law . 7
1.3.6 Ratings and characteristics . 7
1.3.7 Marking . 8
1.3.8 Ordering information . 8
1.3.9 Additional information (not for inspection purposes) . 8
1.4 Marking . 8
1.4.1 General . 8
1.4.2 Marking for potentiometers . 8
1.4.3 Marking for packaging . 8
1.4.4 Additional marking . 8
2 Preferred ratings, characteristics and test severities . 9
2.1 Preferred characteristics . 9
2.1.1 General . 9
2.1.2 Preferred climatic categories . 9
2.1.3 Temperature coefficients and temperature characteristics of resistance . 9
2.1.4 Limits for change in resistance or output voltage ratio . 10
2.1.5 Total mechanical travel . 11
2.2 Preferred values of ratings . 11
2.2.1 General . 11
2.2.2 Nominal total resistance . 11
2.2.3 Tolerances on nominal total resistance . 12
2.2.4 Rated dissipation . 12
2.2.5 Limiting element voltage . 13
2.2.6 Insulation voltage . 13
2.2.7 Limits for insulation resistance . 13
2.3 Preferred test severities . 13
2.3.1 General . 13
2.3.2 Drying . 13
2.3.3 Vibration . 14
2.3.4 Shock . 14
2.3.5 Low air pressure . 14
2.3.6 Change of temperature . 14
3 Quality assessment procedures . 14
3.1 General . 14
3.2 Definitions. 14
3.2.1 Primary stage of manufacture . 14
3.2.2 Structurally similar components . 14

3.2.3 Assessment levels EZ and FZ (zero nonconforming) . 15
3.3 Qualification approval . 15
3.3.1 General . 15
3.3.2 Qualification approval on the basis of the fixed sample size procedure . 15
3.3.3 Tests . 16
3.4 Quality conformance inspection . 23
3.4.1 Formation of inspection lots . 23
3.4.2 Test schedule . 23
3.4.3 Assessment levels . 23
3.5 Delayed delivery . 26
Bibliography . 27

Figure 1 – Rated dissipation curve . 12
Figure 2 – Rated dissipation curve . 13

Table 1 – Temperature coefficients and temperature characteristics of resistance . 10
Table 2 – Limits for change in resistance or output voltage ratio . 11
Table 3 – Fixed sample size test schedule for qualification approval (1 of 7) . 17
Table 4 – Quality conformance inspection: Lot-by-lot inspection . 24
Table 5 – Quality conformance inspection: Periodic testing (1 of 2). 25

– 4 – IEC 60393-2:2015  IEC 2015
INTERNATIONAL ELECTROTECHNICAL COMMISSION
______________
POTENTIOMETERS FOR USE IN ELECTRONIC EQUIPMENT –

Part 2: Sectional specification – Lead-screw actuated
and rotary preset potentiometers

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
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Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
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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 60393-2 has been prepared by IEC technical committee 40:
Capacitors and resistors for electronic equipment.
This third edition cancels and replaces the second edition published in 1989 and constitutes a
technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) revision of the information on the assessment level EZ and FZ (zero nonconforming);
b) complete editorial revision.

The text of this standard is based on the following documents:
FDIS Report on voting
40/2407/FDIS 40/2422/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This International Standard is to be used in conjunction with IEC 60393-1:2008.
A list of all parts in the IEC 60363 series, published under the general title Potentiometers for
use in electronic equipment, can be found on the IEC website.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 6 – IEC 60393-2:2015  IEC 2015
POTENTIOMETERS FOR USE IN ELECTRONIC EQUIPMENT –

Part 2: Sectional specification – Lead-screw actuated
and rotary preset potentiometers

1 General
1.1 Scope
This part of IEC 60393 applies to lead-screw actuated and rotary preset potentiometers,
wirewound and non-wirewound for use in electronic equipment. These potentiometers are
primarily intended for use in circuits for trimming purposes which require infrequent
adjustments.
This part of IEC 60393 prescribes preferred ratings and characteristics and selects from
IEC 60393-1 the appropriate quality assessment procedures, tests and measuring methods. It
provides general performance requirements for this type of potentiometer.
This standard gives the minimum performance requirements and test severities.
1.2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60062, Marking codes for resistors and capacitors
IEC 60068-1:2013, Environmental testing – Part 1: General and guidance
IEC 60068-2-1:2007, Environmental testing – Part 2-1: Tests – Test A: Cold
IEC 60068-2-2:2007, Environmental testing – Part 2-2: Tests – Test B: Dry heat
IEC 60393-1:2008, Potentiometers for use in electronic equipment – Part 1: Generic
specification
IEC 61193-2:2007, Quality assessment systems – Part 2: Selection and use of sampling
plans for inspection of electronic components and packages
1.3 Information to be given in a detail specification
1.3.1 General
Detail specifications shall be derived from the relevant blank detail specification.
Detail specifications shall not specify requirements inferior to those of the generic, sectional
or blank detail specification. When severer requirements are included, they shall be listed in a
subclause of the detail specification and indicated in the test schedules, for example by an
asterisk.
The information given in 1.3.2 and 1.3.4 may, for convenience, be presented in tabular form.

The following information shall be given in each detail specification and the values quoted
shall preferably be selected from those given in the appropriate clause of this sectional
specification.
1.3.2 Outline drawing and dimensions
The detail specification shall incorporate an illustration of the potentiometer being specified.
Where space is insufficient to show the detail dimensions required for inspection purposes,
such dimensions shall appear on a drawing forming an annex to the detail specification.
All dimensions shall preferably be stated in millimetres, however, when the original
dimensions are still given in inches, the converted metric dimensions in millimetres shall be
added.
When the potentiometer is not designed for use on printed boards, this shall be clearly
indicated in the detail specification.
1.3.3 Mounting
The detail specification shall specify the method of mounting to be applied for the voltage
proof and the insulation resistance tests and for the application of the vibration and shock
tests. The potentiometers shall be mounted by their normal means, but the design may be
such that special mounting fixtures are required. In this case the detail specification shall
describe the mounting fixtures and they shall be used for the voltage proof and the insulation
resistance tests and for the application of the vibration and shock tests. For the latter tests
the mounting shall be such that there shall be no parasitic vibration.
1.3.4 Style
See IEC 60393-1:2008, 2.2.2.
The style shall be presented by a double-letter code, e.g. AB, which is arbitrarily chosen for
each detail specification.
The style designation, therefore, has no meaning unless the number of the detail specification
is also given.
1.3.5 Resistance law
The resistance law is generally not verified. If required, the detail specification shall prescribe
the measuring points and the associated limits for the output ratio and shall specify the
position of the corresponding tests in the test schedules.
1.3.6 Ratings and characteristics
1.3.6.1 General
The ratings and characteristics shall be in accordance with the relevant clauses of this
standard together with 1.3.6.2.
1.3.6.2 Nominal total resistance
See IEC 60393-1:2008, 2.3.2.
When products approved according to the detail specification have different ranges, the
following statement should be added:
“The range of values available in each style is given in the register of approvals, available for
.
example on the website http://www.iecq.org/

– 8 – IEC 60393-2:2015  IEC 2015
The qualified products list “QPL” style is given in the register of approvals, available, for
example, on the website as stated above.
1.3.7 Marking
The detail specification shall specify the content of the marking on the potentiometer and on
the package. Deviations from 1.4 of this sectional specification shall be specifically stated.
1.3.8 Ordering information
The detail specification shall indicate that the following information, in clear or in coded form,
is required when ordering:
a) nominal total resistance and tolerance on nominal total resistance;
b) resistance law (if other than linear);
c) number and issue reference of the detail specification and style reference.
1.3.9 Additional information (not for inspection purposes)
The detail specification may include information which is not required to be verified by the
inspection procedure, such as circuit diagrams, curves, drawings and notes needed for the
clarification of the detail specification.
1.4 Marking
1.4.1 General
When coding is used for nominal resistance, tolerance and date of manufacture, the method
shall be selected from those given in IEC 60062.
The information given in the marking is normally selected from the following list. The relative
importance of each item is indicated by its position in the list:
a) nominal total resistance;
b) tolerance on nominal total resistance;
c) resistance law (if other than linear);
d) detail specification and style reference;
e) year and month (or week) of manufacture;
f) manufacturer's name and/or trademark;
g) manufacturer’s type designation.
1.4.2 Marking for potentiometers
The potentiometer shall be clearly marked with a) and b) of 1.4.1 and with as many of the
remaining items as is practicable. Any duplication of information in the marking of the
potentiometer should be avoided.
1.4.3 Marking for packaging
The package containing the potentiometer(s) shall be clearly marked with all the information
listed in 1.4.1 and below.
a) quantity
b) country origin
1.4.4 Additional marking
Any additional marking shall be so applied that no confusion can arise.

2 Preferred ratings, characteristics and test severities
2.1 Preferred characteristics
2.1.1 General
The values given in the detail specification shall preferably be selected from the following:
2.1.2 Preferred climatic categories
The potentiometers covered by this standard are classified into climatic categories according
to the general rules given in IEC 60068-1:2013, Annex A.
The lower and upper category temperature and the duration of the damp heat, steady state
test shall be chosen from the following:
Lower category temperature: –65 °C, –55 °C, –40 °C, –25 °C and –10 °C.
Upper category temperature +70 °C, +85 °C, +100 °C, +125 °C and +155 °C.
Duration of the damp heat, steady state test: 4, 10, 21 and 56 days.
The severities for the cold and dry heat tests are the lower and upper category temperatures
respectively. Because of the construction of some potentiometers these temperatures will
occur between two of the preferred temperatures given in IEC 60068-2-1:2007 and
IEC 60068-2-2:2007. In this case the nearest preferred temperature within the actual
temperature range of the potentiometer shall be chosen for this severity.
2.1.3 Temperature coefficients and temperature characteristics of resistance
The limits of change in resistance for the preferred temperature characteristics of resistance
are given in Table 1.
Each line in the table gives the preferred temperature coefficients and corresponding
temperature characteristics for 20 °C to 70 °C and limits of change in resistance for
measurement of the temperature characteristics of resistance (see IEC 60393-1:2008, 4.14)
on the basis of the category temperature ranges of 2.1.2.
Different portions of the resistance range may be covered by different temperature
characteristics (or coefficients) of resistance although they appear in a single detail
specification.
If measurements at additional temperatures are required, they shall be specified in the detail
specification.
– 10 – IEC 60393-2:2015  IEC 2015
Table 1 – Temperature coefficients and temperature characteristics of resistance
Tempera- Temperature Temperature characteristics of resistance
ture characteristics (limits of resistance change in percentage)
coeffi- of resistance %
cients of
Reference temperature/ Reference temperature/
resistance
Lower category temperature Upper category temperature
–6
10 /K % °C °C
a
20 °C / 70 °C 20/85 20/100 20/125 20/155
+20/–65 +20/–55 +20/–40 +20/–25 +20/–10
–5,2/ –8,4/ –10,8/
–800/ –4/ +6,8/ +6/ +4,8/ +3,6/ +2,4/ –6,4/
– – –
–2 500 –12,5 –20
+21,3 +18,75 +15 +11,3 +7,5
16,25 26,25 33,75
–4,2/
–400/ –2/ +3,4/ +3/ +2,4/ +1,8/ +1,2/ –2,6/ –3,2/ –5,4/
–
–1 000 –5 +8,5 +7,5 +6 +4,5 +3 –6,5 –8 –13,5
10,25
–150/ -0,75/ +1,3/ +1,13/ +0,9/ +0,68/ +0,45/ –0,98/ –1,2/ –1,58/ –2,02/
– 600 -3 –3,9 –4,8 –6,3 –8,2
+5,1 +4,5 +3,6 +2,7 +1,8
±1 000 ±5 ±8,5 ±7,5 ±6 ±4,5 ±3 ±6,5 ±8 ±10,5 ±13,5
±500 ±2,5 ±4,3 ±3,75 ±3 ±2,25 ±1,5 ±3,25 ±4 ±5,25 ±6,75
±250 ±1,25 ±2,15 ±1,88 ±1,5 ±1,13 ±0,75 ±1,62 ±2 ±2,62 ±3,38
±150 ±0,75 ±1,3 ±1,15 ±0,9 ±0,68 ±0,45 ±0,98 ±1,2 ±1,6 ±2,05
±100 ±0,5 ±0,85 ±0,75 ±0,6 ±0,45 ±0,3 ±0,65 ±0,8 ±1,05 ±1,35
±50 ±0,25 ±0,43 ±0,375 ±0,3 ±0,23 ±0,15 ±0,325 ±0,4 ±0,525 ±0,675
±25 ±0,125 ±0,215 ±0,188 ±0,15 ±0,113 ±0,075 ±0,162 ±0,2 ±0,262 ±0,34
a
Potentiometers having an upper category temperature of 85 °C need not be measured between 20 °C and
70 °C.
2.1.4 Limits for change in resistance or output voltage ratio
The preferred combinations of limits for change in resistance or output voltage ratio in each of
the tests listed in the heading of Table 2 are as indicated in the lines of the table.

Table 2 – Limits for change in resistance or output voltage ratio
Stability 4.38 4.34 4.30 4.43.2 4.22 4.35
class Climatic Change of Robustness Electrical Thrust and Vibration
sequence temperature of terminals endurance pull on shaft
%
at 70 °C
4.39 4.33 4.34
Damp heat, Resistance to 4.43.3 Change of
steady state soldering heat Electrical temperature
4.37
endurance at
4.40 4,35
upper category Shock
Mechanical Vibration
temperature
endurance
4.37
4.43.2 Shock
Electrical
endurance at
70 °C
4.43.3
Electrical
endurance at
upper category
temperature
∆ R between
U U
ab ab
a, b a, b
c terminations
∆ ∆
∆ R between terminals a and c
a c
a and b
U U
ac ac
±(10 % R + 0,5 Ω) ±(5 % R + 0,1 Ω) ±(5 % R + 0,1 Ω) ±(15 % R + 0,5 Ω) ±5 % ±7,5 %
±(5 % R + 0,1 Ω) ±(3 % R + 0,1 Ω) ±(2 % R + 0,1 Ω) ±(7,5 % R + 0,1 Ω) ±2 % ±3 %
±(3 % R + 0,1 Ω) ±(2 % R + 0,1 Ω) ±(1 % R + 0,05 Ω) ±(5 % R + 0,1 Ω) ±1 % ±2 %
±(2 % R + 0,1 Ω) ±(2 % R + 0,1 Ω) ±(1 % R + 0,05 Ω) ±(3 % R + 0,1 Ω) ±1 % ±2 %
The clause numbers in the table refer to IEC 60393-1:2008.
a
For wirewound potentiometers, the value of resolution specified in the detail specification shall be added to
the permissible output ratio limits or the permissible change in resistance limits for all tests.
U
ab
b
The setting stability change in the output voltage ratio ∆ shall be expressed in percent of the total
U
ac
applied voltage.
c
∆R indicate the value of change in resistance.

2.1.5 Total mechanical travel
The preferred values shall be:
a) for lead-screw actuated preset potentiometers:
2 to 25 turns;
b) for single-turn rotary preset potentiometers:
the angle shall be specified in the detail specification.
2.2 Preferred values of ratings
2.2.1 General
The values given in detail specifications shall preferably be selected from the following:
2.2.2 Nominal total resistance
See IEC 60393-1:2008, 2.3.2.
– 12 – IEC 60393-2:2015  IEC 2015
2.2.3 Tolerances on nominal total resistance
The preferred tolerances on nominal total resistance are:
±30 %, ±25 %, ±20 %, ±10 % and ±5 %.
2.2.4 Rated dissipation
The preferred values of rated dissipation at 70 °C are:
0,05 W, 0,063 W, 0,1 W, 0,125 W, 0,15 W, 0,2 W, 0,25 W, 0,3 W, 0,5 W, 0,75 W and 1 W.
The derated values of dissipation at temperatures in excess of 70 °C shall be as indicated by
the curve as shown in Figure 1.
Percentage of the
Area of recommended
rated dissipation
operation
Upper category
Lower category + 70 °C
temperature
temperature
IEC
Figure 1 – Rated dissipation curve
A smaller (or larger) area of operation may be given in the detail specification. In this event,
the detail specification shall state the maximum allowable dissipation at temperature other
than 70 °C. All break points on the curve shall be verified by test.
A derating curve having examples of smaller areas of operation (carbon composition) is given
in Figure 2.
Percentage of the
rated dissipation
(1) (2) (3)
LCT UCT
+ 50 °C   + 70 °C  + 85 °C  +  100 °C
IEC
The differences between (1), (2) and (3) depend on the substrate, whereby
(1) = Phenolic resin (multi-layer),
(2) = Resin molded and
(3) = Alumina
Key:
LCT = Lower category temperature
UCT = Upper category temperature
Figure 2 – Rated dissipation curve
2.2.5 Limiting element voltage
The preferred values of limiting element voltage d.c. or a.c. (r.m.s.) are:
100 V, 125 V, 150 V, 200 V, 250 V and 300 V.
2.2.6 Insulation voltage
The detail specification shall prescribe the value of the insulation voltage, rounded off to the
nearest 10 V. The numerical value of the insulation voltage shall be:
Normal air pressure: ≥1,42 times the limiting element voltage.
Low air pressure (at 8 kPa): ≥two-thirds the value at normal air pressure.
2.2.7 Limits for insulation resistance
Unless otherwise specified in the detail specification the insulation resistance shall be not
less than 1 GΩ after dry heat tests and 100 MΩ after humidity tests.
2.3 Preferred test severities
2.3.1 General
Test severities given in the detail specification shall preferably be selected from the following:
2.3.2 Drying
See IEC 60393-1:2008, 4.3, Procedure 1 shall be used.

– 14 – IEC 60393-2:2015  IEC 2015
2.3.3 Vibration
See IEC 60393-1:2008, 4.35, with the following details:
Frequency range: 10 Hz to 55 Hz, or
10 Hz to 500 Hz, or
10 Hz to 2 000 Hz.
Amplitude: 0,75 mm or acceleration 100 m/s (whichever is the less severe)
Sweep endurance: Total duration: 6 h
The detail specification shall prescribe the mounting method to be used. (See 1.3.3)
2.3.4 Shock
See IEC 60393-1:2008, 4.37, with the following details:
Pulse shape: Half-sine
Acceleration: 500 m/s
Pulse duration: 11 ms
Severity: 3 successive shocks to be applied in each of the three directions (total
3 shocks)
The detail specification shall prescribe the mounting method to be used (see 1.3.3).
2.3.5 Low air pressure
See IEC 60393-1:2008, 4.38.5, with the following details:
Air pressure: 8 kPa.
2.3.6 Change of temperature
See IEC 60393-1:2008, 4.34, with the following details:
The duration of the exposure at the extremes of temperature shall be 30 min.
3 Quality assessment procedures
3.1 General
See IEC 60393-1:2008, Clause H.1.
3.2 Definitions
3.2.1 Primary stage of manufacture
For preset potentiometers, primary stage of the manufacture is:
– For film types: The deposition of the resistive film on the substrate.
– For carbon composition types: The process which produces the greatest change
polymerization of the binder.
– For wire-wound types: The winding of the resistance wire on the mandrel insulation or
insulated.
3.2.2 Structurally similar components
Preset potentiometers are considered as being structurally similar if they are potentiometers
produced with the same or similar processes and materials, and that have the same nominal

dimensions but have different resistance values and temperature characteristics (or
coefficients) of resistance.
3.2.3 Assessment levels EZ and FZ (zero nonconforming)
Assessment levels EZ and FZ meet the requirements of “zero nonconforming” approach. They
have been introduced to align the assessment procedures and levels with current industry
practices by prescribing the permitted number of nonconforming items (acceptance number) c
as zero.
Therefore the sample size for lot-by-lot testing is determined by IEC 61193-2:2007, Table 1.
3.3 Qualification approval
3.3.1 General
The procedures for qualification approval testing are given in IEC 60393-1:2008, Clause H.5.
The schedule to be used for qualification approval testing on the basis of lot-by-lot and
periodic test is given in 3.4.
The procedure using a fixed sample size schedule is given in 3.3.2 and 3.3.3 below.
3.3.2 Qualification approval on the basis of the fixed sample size procedure
Sampling
The fixed sample size procedure is described in IEC 60393-1:2008, H.5.3 b). The sample
shall be representative of the range of values for which approval is sought. This may or may
not be the complete range covered by the detail specification.
The sample shall consist of specimens having the highest and lowest resistance values for
which approval is being sought. It should also include the specimens having the critical
resistance value, if this is within the range being submitted. When approval is being sought
for more than one temperature coefficient (or characteristics) of resistance, the sample shall
contain specimens representative of the different temperature coefficients (or characteristics)
of resistance. In a similar manner, the sample should contain a proportion of specimens of the
different resistance values having the closest tolerance for which approval is being sought.
The proportion of specimens having the different characteristics shall be proposed by the
manufacturers chief inspector and shall be to the satisfaction of a certification body (for example
IECQ CB).
Spare specimens are permitted as follows:
a) One per resistance value and one per each temperature coefficient or temperature
characteristic value which may be used to replace the permitted nonconforming items in
Group 0.
b) One per resistance value and one per each temperature coefficient or temperature
characteristic value which may be used to replace specimens which are nonconforming
because of incidents not attributable to the manufacturer. The number given in Group 0
assume that all groups are applicable.
When additional groups are introduced into the qualification approval test schedule, the
number of specimens required for Group 0 shall be increased by the same number as that
required for the additional groups.

– 16 – IEC 60393-2:2015  IEC 2015
3.3.3 Tests
The complete series of tests specified in Table 3 are required for the approval of
potentiometers covered by one detail specification. The tests of each group shall be carried
out in the given order.
The whole sample shall be subjected to the tests of Group 0 and then divided for the other
groups.
Specimens found non-conforming during the test of Group 0 shall not be used for the other
groups.
"One nonconforming item" is counted when a potentiometer has not satisfied the whole or a
part of the tests of a group.
The approval is granted when the number of nonconforming items does not exceed the
specified number of permissible nonconforming items for each group or sub-group and the
total number of permissible non-conformances.
In Table 3 the fixed sample size test schedule is given. It includes details of sampling and
permissible nonconforming items for different tests for groups of tests and gives, together with
the details of the test contained in IEC 60393-1:2008, Clause 4, and Clause 2 of this standard,
a complete summary of test conditions and performance requirements.
It is indicated in Table 3, where, for the test methods, test conditions and/or performance
requirements, a choice shall be made in the detail specification.
The conditions of test and the performance requirements for the fixed sample size test
schedule shall be identical to those prescribed in the detail specification for quality
conformance inspection.
Table 3 – Fixed sample size test schedule for qualification approval (1 of 7)
D Sample size Performance
a
and criterion of requirements
Subclause number
or a
b
Conditions of test
a
acceptability
and test
b
ND
n c
g
GROUP 0
ND 114 0
4.4.1 Visual As in 4.4.1
examination
Legible marking and as
specified in the detail
specification
4.6 Element   As in 4.6.3
resistance
4.4.2 Dimensions   See detail specification
(gauging)
Resistance between a and b
4.7 Terminal R ≤ . Ω
resistance
Resistance between b and c
R ≤ . Ω
4.4.4 Total mechanical  - Lead screw styles
≥70 % of total mechanical
travel Effective operating turns.
travel
- Rotary styles
See detail specification
4.4.6 Effective electrical - Lead screw styles
≥70 % of the measured
travel  total mechanical travel
- Rotary styles See detail specification
c
4.5 Continuity    As in 4.5.1 or 4.5.2
4.15 Rotational noise Method B or Method C  ≤ . % or . Ω
As in 4.12.5
4.12 Voltage proof
(Insulated
Normal air pressure
potentiometers
h
only)
Spare specimens  5
GROUP 1
D 20 0
4.18 Starting torque See detail specification
4.32 Solderability            Solder bath method  Good tinning as evidenced
by free flowing of the
Temperature and duration:
solder with wetting of the
SnPb: (235 ± 5) °C, (2 ± 0,5) s terminals.
SnAgCu: (245 ± 5) °C, (3 ± 0,3) s
4.45 Solvent Solvent:  See detail specification
resistance of the Solvent temperature: .

marking Method 1
(if applicable) Rubbing material: cotton wool
Legible marking
Recovery: .
4.14 Temperature Lower category  ∆R/R ≤ . %
characteristic of temperature/20 °C
resistance
20 °C / 70 °C  ∆R/R ≤ . %
20 °C / Upper category
∆R/R ≤ . %
temperature
4.21 Locking torque Output voltage ratio
U
ab
(if applicable)
∆ ≤ . %
U
ac
Visual examination
As in 4.21.2
– 18 – IEC 60393-2:2015  IEC 2015
Table 3 (2 of 7)
D Sample size Performance
a
and criterion of requirements
Subclause number or
a
b
Conditions of test
a
acceptability
and test
N
b
n c
D
4.20 End stop torque  - For types fitted with end  As in 4.20.1
stops: As specified in
4.20.1
Not less than five times
the upper limit of the
starting torque (Unless
otherwise stated by the
detail specification)
As in 4.20.2
- For types fitted with
slipping clutches:
As specified in 4.20.2
4.22 Thrust and pull on Only the thrust shall be
shaft applied. The pull is not
applicable
- Half of the specimens
As specified in 4.22.2 As in 4.22.2

Continuity
- Remaining specimens
As in 4.22.3
As specified in 4.22.3
U
ab
Setting stability (output
∆ ≤ . %
voltage ratio) (as in
U
ac
4.17.2.1)
4.40 Mechanical Number of cycles: 200
endurance Rate:
(potentiometers)
- Rotary types: 5 to 10
cycles per minute
- Lead screw types:.
As in 4.40.6
Visual examination
∆R ≤ ±(. % + . Ω)
Element resistance
Starting torque . mN･m to . mN･m
Rotational noise,
Method B or Method C Method B: ≤ . % or . Ω
(whichever is greater)
Method C: ≤ . Ω
GROUP 2 D 24 0
(12 of 0
the
sample)
4.30 Robustness of The test appropriate to the
terminals type of terminal
Visual examination As in 4.30.8
Element resistance
∆R ≤
...