Method of measurement of current noise generated in fixed resistors

IEC 60195:2016 specifies a method of measurement and associated test conditions to assess the "noisiness", or magnitude of current noise, generated in fixed resistors of any given type. The method applies to all classes of fixed resistors. The aim is to provide comparable results for the determination of the suitability of resistors for use in electronic circuits having critical noise requirements. This edition includes the following significant technical changes with respect to the previous edition:
- harmonization of the allocation of isolation resistors RM in the recommended operating conditions given in Table 2;
- correction of erroneous numeric values of the contribution of system noise, f(T - S) in Table 3;
- addition of advice on the prescription of requirements in a relevant component specification;
- addition of a set of recommended measuring conditions for specimens with a rated dissipation of less than 100 mW;
- complete editorial revision.

Méthode pour la mesure du bruit produit en charge par les résistances fixes

L'IEC 60195:2016 spécifie une méthode de mesure et des conditions d'essai associées pour évaluer l'absence de bruit ou l'amplitude du bruit en charge généré dans des résistances fixes d'un type quelconque. La méthode s'applique à toutes les classes de résistances fixes. Elle a pour but de fournir des résultats comparables pour déterminer l'aptitude des résistances utilisées dans des circuits électroniques dont les exigences relatives au bruit sont critiques. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
- harmonisation de l'affectation des résistances d'isolement RM dans les conditions de fonctionnement recommandées données dans le Tableau 2;
- correction des valeurs numériques erronées de la contribution du bruit du système, f(T - S) dans le Tableau 3;
- ajout d'un conseil pour prescrire des exigences dans une spécification de composant applicable;
- ajout d'un ensemble de conditions de mesure recommandées pour des spécimens dont la dissipation assignée est inférieure à 100 mW;
- révision éditoriale complète.

General Information

Status
Published
Publication Date
06-Apr-2016
Current Stage
PPUB - Publication issued
Start Date
07-Apr-2016
Completion Date
07-Apr-2016
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IEC 60195
Edition 2.0 2016-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Method of measurement of current noise generated in fixed resistors
Méthode pour la mesure du bruit produit en charge par les résistances fixes
IEC 60195:2016-04(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 60195
Edition 2.0 2016-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Method of measurement of current noise generated in fixed resistors
Méthode pour la mesure du bruit produit en charge par les résistances fixes
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 31.040.10 ISBN 978-2-8322-3272-9

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 60195:2016  IEC 2016
CONTENTS

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

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

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

3 Terms and definitions .................................................................................................... 6

4 Method of measurement ................................................................................................ 7

4.1 Noise basics ......................................................................................................... 7

4.1.1 Noise ............................................................................................................. 7

4.1.2 Thermal noise ................................................................................................ 8

4.1.3 Current noise ................................................................................................. 8

4.2 Measurement principle .......................................................................................... 9

4.3 Measurement system .......................................................................................... 10

4.3.1 Proposal of a suitable measuring system ...................................................... 10

4.3.2 Alternative measuring systems ..................................................................... 11

4.4 Measurement system requirements ..................................................................... 11

4.4.1 Input circuit .................................................................................................. 11

4.4.2 Isolation resistor R ..................................................................................... 12

4.4.3 DC voltage source ....................................................................................... 12

4.4.4 DC electronic voltmeter ................................................................................ 12

4.4.5 Calibration resistor R ............................................................................... 12

Cal

4.4.6 Calibration source ........................................................................................ 13

4.4.7 Determination of the calibration voltage ........................................................ 13

4.4.8 AC band-pass amplifier ................................................................................ 15

4.4.9 AC r.m.s. meter ............................................................................................ 16

4.4.10 Test fixture .................................................................................................. 16

4.5 Verification of the measuring system ................................................................... 17

4.5.1 Performance check by measurement of instrument and thermal noise ........... 17

4.5.2 Performance check by comparison of repeated measurements ...................... 17

5 Measurement procedure .............................................................................................. 18

5.1 Ambient conditions .............................................................................................. 18

5.2 Preparation of specimen ...................................................................................... 18

5.3 Procedure ........................................................................................................... 18

5.3.1 General ....................................................................................................... 18

5.3.2 Calibration ................................................................................................... 18

5.3.3 Measurement of system noise S ................................................................... 18

5.3.4 Measurement of total noise T ....................................................................... 19

5.4 Precautions ......................................................................................................... 22

6 Evaluation of measurement results ............................................................................... 22

6.1 Term for the contribution of system noise ............................................................ 22

6.2 Determination of the current-noise index A ......................................................... 24

6.3 Determination of the current-noise voltage ratio CNR ......................................... 25

6.4 Accuracy ............................................................................................................. 26

6.5 Requirements ...................................................................................................... 26

7 Information to be given in the relevant component specification .................................... 26

Annex A (informative) Letter symbols and abbreviations ..................................................... 27

A.1 Letter symbols .................................................................................................... 27

---------------------- Page: 4 ----------------------
IEC 60195:2016  IEC 2016 – 3 –

A.2 Abbreviations ...................................................................................................... 27

Annex X (informative) Cross-reference for references to the prior revision of this

standard ............................................................................................................................. 28

Bibliography ....................................................................................................................... 29

Figure 1 – Block schematic of a suitable measuring system ................................................. 11

Figure 2 – Typical transfer function of the band-pass amplifier ............................................. 16

Figure 3 – Contribution of system noise, f(T – S) .................................................................. 23

Table 1 – Permissible limits of system noise ........................................................................ 17

Table 2 – Recommended operating conditions (1 of 2) ......................................................... 20

Table 3 – Numeric values of the contribution of system noise, f(T – S) .................................. 24

Table X.1 – Cross reference for references to the 1 edition of this standard ....................... 28

---------------------- Page: 5 ----------------------
– 4 – IEC 60195:2016  IEC 2016
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
METHOD OF MEASUREMENT OF CURRENT
NOISE GENERATED IN FIXED RESISTORS
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

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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

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services carried out by independent certification bodies.

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

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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 60195 has been prepared by IEC technical committee 40:

Capacitors and resistors for electronic equipment.

This second edition cancels and replaces the first edition published in 1965 and constitutes a

technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:

• harmonization of the allocation of isolation resistors R in the recommended operating

conditions given in Table 2;

• correction of erroneous numeric values of the contribution of system noise, f(T − S) in

Table 3;
• addition of advice on the prescription of requirements in a relevant component
specification;

• addition of a set of recommended measuring conditions for specimens with a rated

dissipation of less than 100 mW;
---------------------- Page: 6 ----------------------
IEC 60195:2016  IEC 2016 – 5 –
• complete editorial revision.
The text of this standard is based on the following documents:
FDIS Report on voting
40/2431/FDIS 40/2458/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 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 website 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.
---------------------- Page: 7 ----------------------
– 6 – IEC 60195:2016  IEC 2016
METHOD OF MEASUREMENT OF CURRENT
NOISE GENERATED IN FIXED RESISTORS
1 Scope

This International Standard specifies a method of measurement and associated test

conditions to assess the "noisiness", or magnitude of current noise, generated in fixed

resistors of any given type. The method applies to all classes of fixed resistors. The aim is to

provide comparable results for the determination of the suitability of resistors for use in

electronic circuits having critical noise requirements.

The current noise in resistive materials reflects the granular structure of the resistive material.

For some resistor technologies utilizing homogenous layers it is regarded as providing an

indication of defects, which are considered as a root cause for abnormal ageing of the

component under the influence of temperature and time.

The method described in this International Standard is not a general specification requirement

and therefore is applied if prescribed by a relevant component specification, or, if agreed

between a customer and a manufacturer.
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 60068-1:2013, Environmental testing – Part 1: General and guidance
3 Terms and definitions
For the purposes of this document the following terms and definitions apply.
3.1
current-noise

combination of all random fluctuations of current flow in a resistor which are not attributed to

thermal agitation of the charge carriers (thermal noise) and which depend on the applied

direct current
3.2
current-noise index

logarithmic index of the ratio of the open circuit r.m.s. current-noise voltage in a frequency

decade, in µV, over the d.c. voltage applied under test, in V, used to express the “noisiness”

of an individual resistor

Note 1 to entry: The current-noise index is expressed in dB. The ratio between µV and V is not considered in this

index, leading to its value being 120 dB less than the mathematical current-noise index A ′. This practical index

follows the history of prior revisions of this method.
---------------------- Page: 8 ----------------------
IEC 60195:2016  IEC 2016 – 7 –
3.3
mathematical current-noise index
A ′

logarithmic index of the ratio of the open circuit r.m.s. current-noise voltage in a frequency

decade over the d.c. voltage applied under test, established in consistent units and their

multiples

Note 1 to entry: The mathematical current-noise index is expressed in dB. This index has been introduced for the

mathematical derivation of the considered parameters.
3.4
current-noise voltage ratio
CNR

ratio of the open circuit r.m.s. current-noise voltage in a frequency decade over the d.c.

voltage applied under test, established in µV/V, used to express the “noisiness” of an

individual resistor
3.5
flicker noise
pink noise

random fluctuation present in most electronic devices and typically related to internal

properties of the respective device, which depends on direct current and has a power spectral

density inversely proportional to the frequency
3.6
noise

random fluctuation in an electrical signal having instantaneous amplitude values which, due to

their distribution in a random manner, can only be predicted in terms of probability statements

3.7
shot noise

random fluctuation in electric current due to the flowing current consisting of discrete charges,

which is independent of temperature and has nearly constant power spectral density

throughout the frequency spectrum
3.8
thermal noise

random fluctuation generated by the thermal agitation of the charge carriers (usually the

electrons) inside an electrical conductor at equilibrium, which is independent of any applied

voltage and has nearly constant power spectral density throughout the frequency spectrum

Note 1 to entry: Thermal noise is also referred to as Johnson noise or as Nyquist noise.

4 Method of measurement
4.1 Noise basics
4.1.1 Noise

Noise appears as a spontaneous fluctuating voltage e (t) with instantaneous amplitude

values.

Noise voltage is a statistically independent random variable, where for most kinds of noise the

frequency distribution of amplitudes follows a Gaussian distribution curve. Therefore noise

voltage cannot be predicted except in terms of probability statements.

Usually the characteristic of principal interest is not the instantaneous amplitude value but the

"time-averaged" value.
---------------------- Page: 9 ----------------------
– 8 – IEC 60195:2016  IEC 2016

The measurement of amplitude commonly used and adopted for this International Standard is

the effective (r.m.s.) voltage E observed in a particular frequency pass-band.
4.1.2 Thermal noise

The thermal noise of a resistor is a fluctuating voltage caused by the random motion of

thermally agitated charges, which is present in all resistors. The root mean-square value of

the fluctuating voltage appearing at the open-circuit terminals of a resistor, which would be

indicated by the measuring system, may be calculated using Nyquist’s equation:
E = e = 4 ⋅ k ⋅T ⋅ R ⋅ ∆f
th th
where

E is the effective voltage (r.m.s. voltage) of the thermal noise in a given bandwidth;

e is the momentary voltage of the thermal noise in a given bandwidth;
–23
k is the Boltzmann constant, k ≈ 1,38 × 10 J/K;
T is the absolute temperature;
R is the resistance;
∆f is the bandwidth of the effective band-pass filter of the measuring system.

The presence of thermal noise cannot be ignored because the thermal noise of the resistor

under test is frequently a major source of interference in the measurement.
4.1.3 Current noise

The presence of direct current in a fixed resistor causes an increase in the observed total

noise above the level attributed to thermal noise. Regardless of its originating nature, this

excess noise is referred to as current noise.
2 2 2
E = E + E
t th c
where
E is the effective voltage of the total noise in a given bandwidth;
E is the effective voltage of the thermal noise in a given bandwidth;
E is the effective voltage of the current noise in a given bandwidth.

Hence, the current noise is the geometric difference between the total noise and the thermal

noise
2 2 2
E = E − E
c t th

The effective current-noise voltage per 1 Hz bandwidth is substantially inversely proportional

to frequency
[e( f )] ~
where
e(f) is the momentary voltage of the current noise as a function of frequency;
I is the d.c. current passing through the resistor;
---------------------- Page: 10 ----------------------
IEC 60195:2016  IEC 2016 – 9 –
f is the frequency for which the current noise voltage is considered.

The effective current noise voltage for a given bandwidth is calculated by integrating the

current noise voltage over the frequency band
2 2
E = [e( f )] df
~ df
 
2 2
 
~ I ln
 
 
where
E is the effective voltage of the current noise in a given bandwidth;
f is the lower cut-off frequency of the ideal band-pass;
f is the upper cut-off frequency of the ideal band-pass.

If the mean-square voltage is inversely proportional to frequency, then ideal rectangular pass-

bands having equal ratios of upper to lower band-pass limits transmit equal amounts of noise

voltage from a given noise source.

A resistor exhibiting current noise may be represented as a noise source having a zero-

impedance current-noise voltage generator connected in series with an independent thermal-

noise voltage generator and with a noise-free resistor.
4.2 Measurement principle
E is, in general, closely proportional to the applied d.c. test voltage
The current noise voltage

U . It is recommended, however, to apply a harmonized set of operating conditions in order to

ensure the most comparable measurements for all resistors.

Table 2 gives a set of operating conditions recommended for the testing of resistors with

resistances in the range of 100 Ω to 22 MΩ. The values given therein also avoid overloading

the specimen and the input circuit.

The frequency dependence of noise voltages requires the prescription of a frequency pass-

band to be used in this measurement, which is an ideal rectangular pass-band of one

frequency decade, geometrically centered at 1 000 Hz.

The measurement results in the mathematical current noise index in a frequency decade, A ′,

as follows:
 
 
A = 20lg dB
 
 
 
where

E ′ is the effective open circuit current-noise voltage in a frequency decade, given in V;

U is the d.c. voltage applied to the resistor under test, given in V.
---------------------- Page: 11 ----------------------
– 10 – IEC 60195:2016  IEC 2016

The typical magnitude of the current-noise voltage being in the microvolt range rather than in

a volt range is reflected in the prevalent current noise index in a frequency decade, A ,

 E 
 c 
A = 20lg dB
 
 
where

E is the effective open circuit current-noise voltage in a frequency decade, given in µV;

U is the d.c. voltage applied to the resistor under test, given in V.

The ratio between µV and V, which results in an offset of 120 dB, is neglected in the

traditional definition of the current noise index A , hence the following relationship applies:

A = A − 120 dB .
1 1

Since the current-noise power spectrum approximates to a 1/f frequency characteristic, the

index and the ratio provides an estimate of current noise in any frequency decade.

4.3 Measurement system
4.3.1 Proposal of a suitable measuring system
Figure 1 shows a block schematic of a suitable measuring system.

A three-position switch may be used to access any of the three modes of operation normally

followed in the measurement procedure:
• calibration;
• measurement of system noise;
• measurement of total noise.

The input circuit consists of the resistor under test R , the isolation resistor R and the

T M

calibration resistor R , where the isolation resistor R is required to reduce the shunting

Cal M

effect of the d.c. supply system on the noise generated in the resistor under test.

---------------------- Page: 12 ----------------------
IEC 60195:2016  IEC 2016 – 11 –
N rms
G R
Cal
BPA
IEC
Key
P DC voltage source
G Calibration source, f = 1 kHz
S Three position switch Position 1: Calibration
Position 2: System noise
Position 3: Total noise
R Isolation resistor
R Calibration resistor, R = 1 Ω
Cal Cal
R Resistor under test
U Test voltage, d.c.
BPA Band-pass amplifier with adjustable gain
U Noise voltage, a.c. r.m.s.
N rms
Figure 1 – Block schematic of a suitable measuring system

The following content of this International Standard refers to this suitable measuring system,

unless otherwise specified.
4.3.2 Alternative measuring systems

The proposal of a measuring system in 4.3.1 intends to unify the test and measurement

procedures used for the assessment of the current noise generated in fixed resistors. This

system, however, is not necessarily the only system which can be used, except when

specifically designated as referee or reference methods.
The provider and user of a
...

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