Non-magnetic coatings on magnetic substrates - Measurement of coating thickness - Magnetic method (ISO 2178:2016)

ISO 2178:2016 specifies a method for non-destructive measurements of the thickness of non-magnetizable coatings on magnetizable base metals.
The measurements are tactile and non-destructive on typical coatings. The probe or an instrument with integrated probe is placed directly on the coating to be measured. The coating thickness is displayed on the instrument.
In ISO 2178:2016 the term "coating" is used for material such as, for example, paints and varnishes, electroplated coatings, enamel coatings, plastic coatings, powder coatings, claddings.
NOTE          This method can also be applied to the measurement of magnetizable coatings on non-magnetizable base metals or other materials (see ISO 2361).

Nichtmagnetische Überzüge auf magnetischen Grundmetallen - Messen der Schichtdicke - Magnetverfahren (ISO 2178:2016)

Diese Internationale Norm legt ein Verfahren für zerstörungsfreie Schicht¬dicken¬messungen nichtmagnetischer Beschichtungen auf magnetischen Grundmetallen fest.
Es handelt sich um berührende und zerstörungsfreie Messungen auf üblichen Beschichtungen. Der Prüfkopf oder ein Messgerät mit integrierter Sonde wird direkt auf dem zu messenden Überzug aufgesetzt. Das Messgerät gibt die Schichtdicke an.
In dieser Internationalen Norm wird der Begriff „Beschichtung“ verwendet für Werkstoffe, wie z. B. Lacke und Anstrichstoffe, galvanische Überzüge, Email, Kunststoffschichten, Pulverlacke, Umhüllungen.
ANMERKUNG   Dieses Verfahren kann auch bei Messung magnetisierbarer Überzüge auf nichtmagnetisierbaren Grundmetallen oder anderen Werkstoffen angewandt werden (siehe ISO 2361).

Revêtements métalliques non magnétiques sur métal de base magnétique - Mesurage de l'epaisseur du revêtement - Méthode magnétique (ISO 2178:2016)

ISO 2178:2016 spécifie une méthode de mesurage non destructif de l'épaisseur des revêtements non magnétiques sur des métaux de base magnétiques.
Les mesurages réalisés sur des revêtements types sont tactiles et non destructifs. Le palpeur ou un instrument muni d'un palpeur intégré est placé directement sur le revêtement à mesurer. L'épaisseur du revêtement est affichée sur l'instrument.
Dans l'ISO 2178:2016, le terme «revêtement» est utilisé pour des matériaux tels que, par exemple, des peintures et vernis, des revêtements électrolytiques, des revêtements en émaux, des revêtements en matière plastique, des revêtements en poudre, des placages.
NOTE          Cette méthode peut également être appliquée au mesurage de revêtements magnétiques sur des métaux de base non magnétiques ou d'autres matériaux (voir l'ISO 2361).

Nemagnetne prevleke na magnetnih osnovah - Merjenje debeline prevleke - Magnetna metoda (ISO 2178:2016)

Ta mednarodni standard določa metodo za neporušitvene meritve debeline nemagnetnih prevlek na magnetnih osnovnih kovinah.
Meritve, izvedene na običajnih prevlekah, so otipne in neporušitvene. Sondo ali instrument z vgrajeno sondo se položi neposredno na prevleko, ki se meri. Na instrumentu se prikaže debelina prevleke.
V tem mednarodnem standardu se izraz »prevleka« uporablja za materiale, kot so barve in laki, elektrolitske prevleke, emajlirane prevleke, plastične prevleke, praškaste prevleke in obloge.
OPOMBA: Ta metoda se lahko uporablja tudi za merjenje magnetnih prevlek na nemagnetnih osnovnih kovinah ali drugih materialih (glej standard ISO 2361).

General Information

Status
Published
Publication Date
05-Apr-2016
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Due Date
06-Apr-2016
Completion Date
06-Apr-2016

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SLOVENSKI STANDARD
SIST EN ISO 2178:2016
01-julij-2016
1DGRPHãþD
SIST EN ISO 2178:1999
Nemagnetne prevleke na magnetnih osnovah - Merjenje debeline prevleke -
Magnetna metoda (ISO 2178:2016)

Non-magnetic coatings on magnetic substrates - Measurement of coating thickness -

Magnetic method (ISO 2178:2016)
Nichtmagnetische Überzüge auf magnetischen Grundmetallen - Messen der
Schichtdicke - Magnetverfahren (ISO 2178:2016)

Revêtement métalliques non magnétiques sur métal de base magnétique - Mesurage de

l'epaisseur du revêtement - Méthode maguétique (ISO 2178:2016)
Ta slovenski standard je istoveten z: EN ISO 2178:2016
ICS:
17.040.20 Lastnosti površin Properties of surfaces
25.220.40 Kovinske prevleke Metallic coatings
25.220.50 Emajlne prevleke Enamels
SIST EN ISO 2178:2016 en,fr,de

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

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SIST EN ISO 2178:2016
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SIST EN ISO 2178:2016
EN ISO 2178
EUROPEAN STANDARD
NORME EUROPÉENNE
April 2016
EUROPÄISCHE NORM
ICS 25.220.40; 25.220.50 Supersedes EN ISO 2178:1995
English Version
Non-magnetic coatings on magnetic substrates -
Measurement of coating thickness - Magnetic method (ISO
2178:2016)

Revêtements métalliques non magnétiques sur métal Nichtmagnetische Überzüge auf magnetischen

de base magnétique - Mesurage de l'epaisseur du Grundmetallen - Messen der Schichtdicke -

revêtement - Méthode magnétique (ISO 2178:2016) Magnetverfahren (ISO 2178:2016)
This European Standard was approved by CEN on 27 February 2016.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this

European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references

concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN

member.

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

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

Centre has the same status as the official versions.

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

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

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 2178:2016 E

worldwide for CEN national Members.
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SIST EN ISO 2178:2016
EN ISO 2178:2016 (E)
Contents Page

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

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SIST EN ISO 2178:2016
EN ISO 2178:2016 (E)
European foreword

This document (EN ISO 2178:2016) has been prepared by Technical Committee ISO/TC 107 "Metallic

and other inorganic coatings" in collaboration with Technical Committee CEN/TC 262 “Metallic and

other inorganic coatings” the secretariat of which is held by BSI.

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

identical text or by endorsement, at the latest by October 2016, and conflicting national standards shall

be withdrawn at the latest by October 2016.

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

patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent

rights.
This document supersedes EN ISO 2178:1995.

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

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

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,

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

Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
Endorsement notice

The text of ISO 2178:2016 has been approved by CEN as EN ISO 2178:2016 without any modification

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SIST EN ISO 2178:2016
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SIST EN ISO 2178:2016
INTERNATIONAL ISO
STANDARD 2178
Third edition
2016-03-15
Non-magnetic coatings on magnetic
substrates — Measurement of coating
thickness — Magnetic method
Revêtement métalliques non magnétiques sur métal de base
magnétique — Mesurage de l’epaisseur du revêtement — Méthode
maguétique
Reference number
ISO 2178:2016(E)
ISO 2016
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SIST EN ISO 2178:2016
ISO 2178:2016(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2016, Published in Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form

or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior

written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of

the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2016 – All rights reserved
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SIST EN ISO 2178:2016
ISO 2178:2016(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

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

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

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

4 Principle of measurement .......................................................................................................................................................................... 2

4.1 Basic principle of all magnetic measurement methods ....................................................................................... 2

4.2 Magnetic pull-off method ............................................................................................................................................................... 2

4.3 Magnetic inductive principle ...................................................................................................................................................... 3

4.4 Magnetic flux gauge ............................................................................................................................................................................ 5

5 Factors affecting measurement accuracy ................................................................................................................................... 6

5.1 Basic influence of the coating thickness ........................................................................................................................... 6

5.2 Magnetic properties of the base metal ............................................................................................................................... 6

5.3 Electrical properties of the coating materials .............................................................................................................. 7

5.4 Geometry: base metal thickness .............................................................................................................................................. 7

5.5 Edge effect ................................................................................................................................................................................................... 7

5.6 Geometry: surface curvature ...................................................................................................................................................... 7

5.7 Surface roughness ................................................................................................................................................................................ 8

5.8 Cleanliness: lift-off effect ................................................................................................................................................................ 8

5.9 Probe pressure ........................................................................................................................................................................................ 8

5.10 Probe tilt ....................................................................................................................................................................................................... 8

5.11 Temperature effects ............................................................................................................................................................................ 9

5.12 External electromagnetic fields ................................................................................................................................................ 9

6 Calibration and adjustment of the instrument ..................................................................................................................... 9

6.1 General ........................................................................................................................................................................................................... 9

6.2 Thickness reference standards ................................................................................................................................................. 9

6.3 Methods of adjustment .................................................................................................................................................................10

7 Measurement procedure and evaluation .................................................................................................................................10

7.1 General ........................................................................................................................................................................................................10

7.2 Number of measurements and evaluation ...................................................................................................................11

8 Uncertainty of the results .........................................................................................................................................................................11

8.1 General remarks .................................................................................................................................................................................11

8.2 Uncertainty of the calibration of the instrument ...................................................................................................12

8.3 Stochastic errors .................................................................................................................................................................................13

8.4 Uncertainties caused by factors summarized in Clause 5 .............................................................................. 13

8.5 Combined uncertainty, expanded uncertainty and final result ..................................................................14

9 Precision ....................................................................................................................................................................................................................14

9.1 General ........................................................................................................................................................................................................14

9.2 Repeatability (r) ..................................................................................................................................................................................14

9.3 Reproducibility limit (R) ..............................................................................................................................................................15

10 Test report ................................................................................................................................................................................................................15

Annex A (informative) Basic principle of all measurement methods .............................................................................17

Annex B (informative) Basic performance requirements for coating thickness gauges which

are based on the magnetic method described in this International Standard .................................19

Annex C (informative) Examples of experimental estimation of factors affecting the

measurement .......................................................................................................................................................................................................21

Annex D (informative) Example of uncertainty estimation (see Clause 8) ...............................................................26

Annex E (informative) Basics of the determination of the uncertainty of a measurement of

the used measurement method corresponding to ISO/IEC Guide 98-3 ...................................................29

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SIST EN ISO 2178:2016
ISO 2178:2016(E)

Annex F (informative) Table of the student factor ..............................................................................................................................31

Annex G (informative) Details on precision ...............................................................................................................................................32

Bibliography .............................................................................................................................................................................................................................37

iv © ISO 2016 – All rights reserved
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SIST EN ISO 2178:2016
ISO 2178:2016(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

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

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the meaning of ISO specific terms and expressions related to conformity

assessment, as well as information about ISO’s adherence to the WTO principles in the Technical

Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information

The committee responsible for this document is ISO/TC 107, Metallic and other inorganic coatings.

This third edition cancels and replaces the second edition (ISO 2178:1982), which has been technically

revised.
© ISO 2016 – All rights reserved v
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SIST EN ISO 2178:2016
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SIST EN ISO 2178:2016
INTERNATIONAL STANDARD ISO 2178:2016(E)
Non-magnetic coatings on magnetic substrates —
Measurement of coating thickness — Magnetic method
1 Scope

This International Standard specifies a method for non-destructive measurements of the thickness of

non-magnetizable coatings on magnetizable base metals.

The measurements are tactile and non-destructive on typical coatings. The probe or an instrument with

integrated probe is placed directly on the coating to be measured. The coating thickness is displayed on

the instrument.

In this International Standard the term “coating” is used for material such as, for example, paints and

varnishes, electroplated coatings, enamel coatings, plastic coatings, powder coatings, claddings.

NOTE This method can also be applied to the measurement of magnetizable coatings on non-magnetizable

base metals or other materials (see ISO 2361).
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document. For dated

references, only the edition cited applies. For undated references, the latest edition of the referenced

document (including any amendments) applies.

ISO 2064, Metallic and other inorganic coatings — Definitions and conventions concerning the measurement

of thickness
ISO 4618, Paints and varnishes — Terms and definitions

ISO 5725-1:1994, Accuracy (trueness and precision) of measurement methods and results — Part 1: General

principles and definitions

ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in

measurement (GUM:1995)
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 2064 and ISO 4618 and the

following apply.
3.1
adjustment of a measuring system

set of operations carried out on a measuring system so that it provides prescribed indications

corresponding to given values of a quantity to be measured

Note 1 to entry: Adjustment of a measuring system can include zero adjustment, offset adjustment, and span

adjustment (sometimes called gain adjustment).

Note 2 to entry: Adjustment of a measuring system should not be confused with calibration, which is a

prerequisite for adjustment.

Note 3 to entry: After an adjustment of a measuring system, the measuring system shall usually be recalibrated.

Note 4 to entry: Colloquially the term “calibration” is frequently but falsely used instead of the term “adjustment”.

In the same way, the terms “verification” and “checking” are often used instead of the correct term “calibration”.

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SIST EN ISO 2178:2016
ISO 2178:2016(E)

[SOURCE: ISO/IEC Guide 99:2007, 3.11 (also known as “VIM”), modified – Note 4 to entry has been added.]

3.2
calibration

operation that, under specified conditions, in a first step, establishes a relation between the quantity

values with measurement uncertainties provided by measurement standards and corresponding

indications with associated measurement uncertainties and, in a second step, uses this information to

establish a relation to obtain a measurement result from indication

Note 1 to entry: A calibration may be expressed by a statement, calibration function, calibration diagram,

calibration curve, or calibration table. In some cases, it may consist of an additive or multiplicative correction of

the indication with associated measurement uncertainty.

Note 2 to entry: Calibration should not be confused with adjustment of a measuring system, often mistakenly

called “self-calibration”, nor with verification of calibration.

Note 3 to entry: Often, the first step alone in the above definition is perceived as being calibration.

[SOURCE: ISO/IEC Guide 99:2007, 2.39 (also known as “VIM”)]
4 Principle of measurement
4.1 Basic principle of all magnetic measurement methods

The magnetic flux density close to a magnetic field source (permanent magnet or electromagnet)

depends on the distance to a magnetizable base metal. This phenomenon is used to determine the

thickness of a non-magnetic coating applied to the base metal.
NOTE 1 Annex A describes the physical background of this effect in more detail.

All the methods covered by this International Standard evaluate the magnetic flux density to determine

the thickness of the coating. The strength of the magnetic flux density is converted into corresponding

electrical currents, electrical voltages or mechanical forces depending on the method used. The values

are either pre-processed by digital means or are directly displayed on a usefully scaled gauge.

NOTE 2 The methods described in 4.3 and 4.4 can also be combined in one and the same probe with another

method, e.g. with the eddy current method according to ISO 2360 or ISO 21968.

Annex B describes the basic performance requirements for coating thickness gauges based on the

magnetic method described in this International Standard.
4.2 Magnetic pull-off method

The magnetic flux density of a permanent magnet and thus the attraction force between a permanent

magnet and a magnetizable base metal decreases with increasing distance. In this way, the attraction

force is a direct measure for the coating thickness of interest.

Instruments working with the magnetic pull-off method consist of at least three units:

— a permanent magnet;
— a pull-off device with continuously increasing pull-off force;

— a display or scale for the coating thickness, which is calculated from the pull-off force.

The pull-off force can be generated by different types of springs or an electromagnetic device.

Some instruments are able to compensate the influence of gravity and allow measurements in all

positions.

All other instruments may only be used in the position specified by the manufacturer.

2 © ISO 2016 – All rights reserved
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SIST EN ISO 2178:2016
ISO 2178:2016(E)

The location of measurement shall be clean and free from liquid or pasty coatings. The permanent

magnet shall be free from particles.

Electrostatic charging can cause additional forces on the permanent magnet or the measuring system

and is therefore to be avoided or shall be discharged before the measurement.
Figure 1 shows a magnetic pull-off gauge.
Key
1 base metal
2 coating
3 magnet
4 scale
5 spring
Figure 1 — Magnetic pull-off gauge
4.3 Magnetic inductive principle

The electrical inductivity of a coil changes when an iron core is inserted into the coil or when an iron

object, e.g. a plate, approaches the coil. Therefore, the electrical inductivity can be used as a measure of

the distance between the coil and a ferromagnetic substrate or as a measure of the coating thickness, if

the coil is placed onto a coated magnetizable base metal.

There are many different electronic methods to evaluate changes of the electrical inductivity or

the reaction of a coil system to a ferromagnetic substrate. Magnetic induction probes for thickness

measurements of coatings on magnetizable materials can consist of one or more coils. Most often two

coils are used (see Figure 2): the first (primary coil) to generate a low frequency alternating magnetic

field and the second (secondary coil) to measure the resulting induced voltage U. If the probe is placed

on a coated magnetizable material (µ > 1) the magnetic flux density (see Annex A) and the induced

voltage of the secondary coil vary as a function of the coating thickness. The function between the

induced voltage and the coating thickness is nonlinear and depends on the permeability µ of the base

metal. It is usually determined by a calibration. Calibration curves that assign a coating thickness to the

induced voltages can be stored in the gauge.

Different designs and geometries of these kind of probes are used. Very often both coils are

employed together with a highly magnetizable core in order to increase the sensitivity of the probes

and to concentrate the field. In this way, both the coating area, which contributes to the thickness

measurement, and the influence of the geometry of the coated component are reduced (see 5.5 and 5.6).

On the contrary, a two pole probe (see Figure 3) has a wide and open field distribution. The two-pole

probe has area integrating properties, while a one-pole probe measures locally.
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SIST EN ISO 2178:2016
ISO 2178:2016(E)

Usually the frequency of the generated field is below the kilohertz range, which avoids eddy current

generation if the coatings are conductive. Therefore, both conductive and nonconductive coatings can

be measured by means of this principle.
Key
1 iron core of the probe I exciting current
2 low frequency alternating magnetic field t coating thickness
3 steel/iron substrate U = f(t) measurement signal
4 coating
Figure 2 — Schematic of the magnetic induction principle
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SIST EN ISO 2178:2016
ISO 2178:2016(E)
Key
1 iron core of the probe 4 coating
2 coil system 5 base metal
3 probe tip
Figure 3 — Schematic of a two pole probe
4.4 Magnetic flux gauge

The magnetic flux density close to a magnet depends on the magnetic properties of the substances in

the magnetic field. The magnetic flux density decreases if the fraction of non-magnetizable substances

increases relative to magnetizable substances. This fact is used in magnetic flux gauges (see Figure 4).

The coating (4) is non-magnetizable; the base metal (3) is magnetizable. A magnet (1) creates a

magnetic field. Its field lines pass through both the coating and the base metal. A magnetic flux detector

(5) placed close to the magnet outputs electrical signals, which depends on the coating thickness.

NOTE 1 Magnetic flux detectors are Hall-sensors or magneto resistive sensors.
NOTE 2 The magnet can be a permanent magnet or an electromagnet.
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SIST EN ISO 2178:2016
ISO 2178:2016(E)
Key
1 permanent magnet U output voltage
2 static magnetic field a measurement signal
3 base metal
4 coating
5 Hall element as magnetic flux detector
Figure 4 — Flux gauge using a Hall probe

The electric signals of the flux detector are further processed by electronic means. The function

between flux detector output and the coating thickness is nonlinear and depends on the permeability

µ of the base metal. It is usually determined by calibration. Calibration curves that assign a coating

thickness to the electric detector output can be stored in the gauge.
5 Factors affecting measurement accuracy
5.1 Basic influence of the coating thickness

The sensitivity of a probe, i.e. the measurement effect, decreases with increasing thickness within the

measurement range of the probe. In the lower measurement range this measurement uncertainty (in

absolute terms) is constant, independent of the coating thickness. The absolute value of this uncertainty

depends on the properties of the probe system and the used sample materials, e.g. the homogeneity of

the base metal permeability, the base metal roughness and the sample surface roughness. In the upper

measurement range of the probe the uncertainty becomes relative to the thickness and is approximately

a constant fraction of that thickness.
5.2 Magnetic properties of the base metal
The permeability of the base metal causes the measurement effect of this method.

The relationship between coating thickness and the measured value depends strongly on the

permeability of the base metal. Consequently, calibration procedures and measurements shall be

made on the same material. Different materials with different permeabilities can cause more or fewer

6 © ISO 2016 – All rights
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