Metallic coatings - Measurement of coating thickness - X-ray spectrometric methods (ISO 3497:2000)

Migrated from Progress Sheet (TC Comment) (2000-07-10): Under revision in ISO - PQ postponed. ++ this document must be processed in // with ISO 3497:1986 rev 5.1 . Resolution of ++ TC to be receivedwithin the month(glg-97-03-21) ++ N 201: New TD (980917)

Metallische Schichten - Schichtdickenmessung - Röntgenfluoreszenz-Verfahren (ISO 3497:2000)

1.1 Diese internationale Norm legt Verfahren zur Messung der Dicke metallischer Schichten nach dem Röntgenfluoreszenz-Verfahren fest. 1.2 Die Meßverfahren, für die diese internationale Norm gilt, sind grundlegende Verfahren, bei denen die flächenbezogene Masse bestimmt wird. Bei bekannter Dichte des Schichtwerkstoffs können die Meßergebnisse auch als längenbezogene Schichtdicke angegeben werden. 1.3 Die Meßverfahren erlauben die gleichzeitige Messung von Schichtsystemen mit bis zu drei Schichten, oder die gleichzeitige Messung der Dicke und Zusammensetzung von Schichten mit bis zu drei Bestandteilen.

Revetements métalliques - Mesurage de l'épaisseur du revetement - Méthodes par spectrométrie de rayons X (ISO 3497:2000)

AVERTISSEMENT : La présente Norme internationale ne traite pas des problèmes de protection du personnel contre les rayons X. Pour tout renseignement sur cet aspect essentiel, il convient de se référer aux Normes internationales et normes nationales, ainsi qu'aux codes locaux, s'il en existe.  La présente Norme internationale spécifie des méthodes de mesurage, par spectrométrie de rayons X, de l'épaisseur des revêtements métalliques.  Les méthodes de mesurage de la présente Norme internationale sont applicables, avant tout, à la détermination de la masse de revêtement par unité de surface. Connaissant la masse volumique du matériau de revêtement, il est possible, également, d'exprimer les résultats mesurés en épaisseur linéaire de revêtement.  Les méthodes de mesurage permettent de mesurer simultanément les systèmes de revêtement ayant jusqu'à trois couches, ou de mesurer simultanément l'épaisseur et les compositions des couches ayant jusqu'à trois composants.  Les plages pratiques de mesurage des matériaux de revêtement indiqués sont largement fonction de la puissance de la fluorescence X caractéristique à analyser et de l'incertitude de mesure tolérée, et peuvent différer selon l'appareillage et le mode opératoire utilisés.

Kovinske prevleke - Merjenje debeline prevleke - Rentgenska spektrometrijska metoda (ISO 3497:2000)

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SIST EN ISO 3497:2002
Kovinske prevleke - Merjenje debeline prevleke - Rentgenska spektrometrijska
metoda (ISO 3497:2000)
Metallic coatings - Measurement of coating thickness - X-ray spectrometric methods
(ISO 3497:2000)
Metallische Schichten - Schichtdickenmessung - Röntgenfluoreszenz-Verfahren (ISO
Revetements métalliques - Mesurage de l'épaisseur du revetement - Méthodes par
spectrométrie de rayons X (ISO 3497:2000)
Ta slovenski standard je istoveten z: EN ISO 3497:2000
17.040.20 Lastnosti površin Properties of surfaces
25.220.40 Kovinske prevleke Metallic coatings
SIST EN ISO 3497:2002 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 3497:2002

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SIST EN ISO 3497:2002
EN ISO 3497
December 2000
ICS 25.220.40
English version
Metallic coatings - Measurement of coating thickness - X-ray
spectrometric methods (ISO 3497:2000)
Revêtements métalliques - Mesurage de l'épaisseur du Metallische Schichten - Schichtdickenmessung -
revêtement - Méthodes par spectrométrie de rayons X (ISO Röntgenfluoreszenz-Verfahren (ISO 3497:2000)
This European Standard was approved by CEN on 15 December 2000.
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 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 Management Centre has the same status as the official
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2000 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 3497:2000 E
worldwide for CEN national Members.

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SIST EN ISO 3497:2002
Page 2
EN ISO 3497:2000
Corrected on 2001-05-16
The text of the International Standard ISO 3497:2000 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 June 2001, and
conflicting national standards shall be withdrawn at the latest by June 2001.
According to the CEN/CENELEC Internal Regulations, the national standards
organizations of the following countries are bound to implement this European
Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany,
Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of the International Standard ISO 3497:2000 was approved by CEN as a
European Standard without any modification.

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SIST EN ISO 3497:2002
Third edition
Metallic coatings — Measurement
of coating thickness — X-ray spectrometric
Revêtements métalliques — Mesurage de l'épaisseur du revêtement —
Méthodes par spectrométrie de rayons X
Reference number
ISO 3497:2000(E)
ISO 2000

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SIST EN ISO 3497:2002
ISO 3497:2000(E)
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ii © ISO 2000 – All rights reserved

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SIST EN ISO 3497:2002
ISO 3497:2000(E)
Contents Page
1 Scope .1
2 Terms and definitions .1
3 Principle.3
4 Apparatus .7
5 Factors that influence the measurement results.10
6 Calibration of instrument .14
7 Procedure .16
8 Measurement uncertainty .17
9 Test report .17
Annex A (informative) Typical measuring ranges for some common coating materials .18
© ISO 2000 – All rights reserved iii

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SIST EN ISO 3497:2002
ISO 3497:2000(E)
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
Draft International Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 3497 was prepared by Technical Committee ISO/TC 107, Metallic and other inorganic
coatings, Subcommittee SC 2, Test methods.
This third edition cancels and replaces the second edition (ISO 3497:1990), which has been technically revised.
Annex A of this International Standard is for information only.
iv © ISO 2000 – All rights reserved

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SIST EN ISO 3497:2002
Metallic coatings — Measurement of coating thickness —
X-ray spectrometric methods
1 Scope
WARNING Problems concerning protection of personnel against X-rays are not covered by this
International Standard. For information on this important aspect, reference should be made to current
international and national standards, and to local regulations, where these exist.
1.1 This International Standard specifies methods for measuring the thickness of metallic coatings by the use of
X-ray spectrometric methods.
1.2 The measuring methods to which this International Standard applies are fundamentally those that determine
the mass per unit area. Using a knowledge of the density of the coating material, the results of measurements can
also be expressed as linear thickness of the coating.
1.3 The measuring methods permit simultaneous measurement of coating systems with up to three layers, or
simultaneous measurement of thickness and compositions of layers with up to three components.
1.4 The practical measurement ranges of given coating materials are largely determined by the energy of the
characteristic X-ray fluorescence to be analysed and by the acceptable measurement uncertainty and can differ
depending upon the instrument system and operating procedure used.
2 Terms and definitions
For the purposes of this International Standard, the following terms and definitions apply.
X-ray fluorescence
secondary radiation occurring when a high intensity incident X-ray beam impinges upon a material placed in the
path of the incident beam
NOTE The secondary emission has wavelengths and energies characteristic of that material.
intensity of fluorescent radiation
radiation intensity, x, measured by the instrument, expressed in counts (radiation pulses) per second
saturation thickness
thickness that, if exceeded, does not produce any detectable change in fluorescent intensity
NOTE Saturation thickness depends upon the energy or wavelength of the fluorescent radiation, density and atomic
number of the material and on the angle of incident and fluorescent radiation with respect to the surface of the material.
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SIST EN ISO 3497:2002
ISO 3497:2000(E)
normalized intensity
ratio of the difference in intensity obtained from a coated specimen, x, and an uncoated substrate material, x ,and
the difference obtained from a material of thickness equal to or greater than the saturation thickness, x (see 2.3)
and an uncoated substrate material, x , all measured under the same conditions
NOTE 1 The mathematical relationship is given by:
x �
x is the intensity obtained from the coated specimen;
x is the intensity obtained from uncoated substrate material;
x is the intensity obtained from a material of thickness equal to or greater than the saturation thickness.
NOTE 2 The normalized intensity is independent of measurement and integration time, and intensity of the excitation
(incident radiation). The geometric configuration and the energy of the excitation radiation can influence the normalized count
rate. The value of x is validbetween0and 1.
intermediate coatings
coatings that lie between the top coating and the basis material and are of thicknesses less than saturation for
each of the coatings
NOTE Any coating lying between the top coating and the basis material (substrate) and having a thickness above
saturation should itself be considered the true substrate since the material under such a coating will not affect the measurement
and can be eliminated for measurement purposes.
count rate
number of radiation pulses recorded by the instrument per unit time (see 2.2).
basis material
basis metal
material upon which coatings are deposited or formed
[ISO 2080:1981, definition 134]
material upon which a coating is directly deposited
NOTE For a single or first coating the substrate is identical with the basis material; for a subsequent coating the
intermediate coating is the substrate.
[ISO 2080:1981, definition 630]
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SIST EN ISO 3497:2002
ISO 3497:2000(E)
3.1 Basis of operation
A relationship exists between mass per unit area of the coating (and thus the linear coating thickness if the density
is known) and the secondary radiation intensity. This relationship, for any practical instrument system, is first
established by calibrating using calibration standards having coatings of known mass per unit area. If the coating
material density is known, such standards can have coatings given in linear thickness units, provided that the
actual density value is also given.
NOTE The coating material density is the density as-coated, which may or may not be the theoretical density of the coating
material at the time the measurement is made. If this density differs from the density of the calibration standards, a factor that
reflects this difference is used and documented in the test report.
The fluorescent intensity is a function of the atomic number of the elements. Providing the top coating, intermediate
coating (if present) and the substrate are of different elements or a coating consists of more than one element,
these elements will generate radiation characteristics for each of them. A suitable detector system can be adjusted
to select either one or more energy bands, enabling the equipment to measure thickness and/or composition of
either the top coating or the top and some intermediate coatings simultaneously.
3.2 Excitation
3.2.1 General
The measurement of the thickness of coatings by X-ray spectrometric methods is based on the combined
interaction of the coating (or coatings) and substrate with an intense, often narrow, beam of polychromatic or
monochromatic X-radiation. This interaction results in generating discrete wavelengths or energies of secondary
radiation which are characteristic of the elements composing the coating(s) and substrate.
The generated radiation is obtained from a high voltage X-ray tube generator or from suitable radioisotopes.
3.2.2 Generation by a high voltage X-ray tube
Suitable excitation radiation will be produced by an X-ray tube if sufficient potential is applied to the tube and stable
conditions apply. Applied voltages are in the order of 25 kV to 50 kV for most thickness requirements but voltages
down to 10 kV may be necessary in order to measure low atomic number coating materials. For some applications
the use of a primary filter, located between the X-ray tube and the specimen, decreases the measurement
The chief advantages of this method of excitation are
� the ability to create, by collimation, a very high intensity beam on a very small measurement area;
� the ease of control for personnel safety requirements;
� the potential stability of emission obtainable by modern electronic methods.
3.2.3 Generation by a radioisotope
Only a few radioisotopes emit gamma radiation in the energy band suitable for coating thickness measurement.
Ideally, the excitation radiation is of slightly higher energy (shorter in wavelength) than the desired characteristic
X-rays. The advantages of radioisotope generation include the possibility of a more compact construction of the
instrument, due mainly to there being no need for cooling. In addition, the radiation, unlike that from high voltage
X-ray generators, is essentially monochromatic and there is low background intensity.
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SIST EN ISO 3497:2002
ISO 3497:2000(E)
The major technical disadvantages when compared with the X-ray tube method are
� the much lower intensity that is obtained, which prohibits measurements on small areas;
� the short half-life of some radioisotopes;
� personnel protection problems associated with high intensity radioisotopes (the high voltage X-ray tube can
simply be switched off).
3.3 Dispersion
3.3.1 General
The secondary radiation resulting from the exposure of a coated surface to X-ray radiation often contains
components additional to those required for the measurement of coating thickness. The desired components are
separated by either wavelength or energy dispersion.
3.3.2 Wavelength dispersion
The wavelength characteristic of either coating or substrate is selected using a crystal spectrometer. Typical
characteristic emission data for commonly used crystals are available in published form from various national
3.3.3 Energy dispersion
X-ray quanta are usually specified in terms of wavelength or equivalent energies. The relationship between the
wavelength, �, in nanometres, and energy E, in kiloelectron-volts (keV), is given by
�� E = 1,239 842 7.
3.4 Detection
The type of detector used for wavelength dispersive systems can be a gas-filled tube, a solid state detector or
scintillation counter connected to a photomultiplier.
The most suitable detector for receiving fluorescent photons and used in energy dispersive systems is selected by
the instrument designer according to the application. In the energy band of about 1,5 keV to 100 keV,
measurements can be made in normal atmosphere without helium gas or vacuum.
Fluorescent radiation of different characteristic energies passes into the energy dispersive detector and then on to
a multi-channel analyser that is adjusted to select the correct energy band.
3.5 Thickness measurement
3.5.1 Emission method
If the intensity of the characteristic radiation from the coating is measured, the intensity increases with increasing
thickness up to the saturation thickness. See Figure 1 a).
When the X-ray emission method is used, the equipment is adjusted to receive a selected band of energies
characteristic of the coating material. Hence thin coatings produce low intensities and thick coatings produce high
3.5.2 Absorption method
If the intensity of the characteristic radiation from the substrate is measured, the intensity decreases with increasing
thickness. See Figure 1 b).
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SIST EN ISO 3497:2002
ISO 3497:2000(E)
The X-ray absorption method uses the band of energies characteristic of the substrate material. Hence thin
coatings result in high intensities and thick coatings produce low intensities. In practice, care has to be taken to
ensure that no intermediate coating is present.
The absorption characteristic is similar to the inverse of the emission characteristic.
a) X-ray emission method b) X-ray absorption method
Figure 1 — Schematic illustrations of the relationship between intensity or count rate and coating
3.5.3 Ratio method
It is possible to combine X-ray absorption and emission when coating thicknesses are expressed as a ratio of the
respective intensities of substrate and coating materials. Measurements by the ratio method are largely
independent of the distance between the test specimen and the detector.
3.5.4 Measurement
For both methods described in 3.5.1 and 3.5.2, the normalized count-rate system is usually used in many
commercially available instruments adjusted so that the count-rate characteristic of the uncoated substrate is zero
and that of an infinitely thick sample of the coating material is unity. All measurable thicknesses therefore produce
count rates that lie within the normalized count-rate range of 0 to 1. See Figure 2.
In all cases, the best or most sensitive range of measurement lies approximately between 0,3 and 0,8 on the
normalized count-rate scale. Thus for best measurement accuracy over the whole thickness range, it is
advantageous to use calibration standards having count-rate characteristics of 0,3 and 0,8. With some equipment
other standards may be necessary in order to ensure precision at other thicknesses. Since the relative uncertainty
of calibration of standards increases as thickness decreases, it is essential to establish the correct mathematical
relationship for the thin end of the range by suitable use of standards having thicker coatings but lower
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SIST EN ISO 3497:2002
ISO 3497:2000(E)
1 Linear range
2 Logarithmic range
3 Hyperbolic range
NOTE 0 = Count rate from saturated (uncoated) substrate material; 1 = count rate from saturated (infinite) coating material.
Figure 2 —Schematic illustration of the relationship between mass per unit area and normalized count rate
3.6 Absorber for secondary radiation
When measuring coating/substrate material combinations that have widely differing energies (energy dispersive
systems), the ratio of saturated coating to uncoated substrate count-rate characteristics is very high (10:1 is
typical). In such cases, it is not always essential to have calibration standards having a similar or the same
substrate (since the substrate material will not radiate in the same energy band as the coating material). When the
uncoated substrate/infinite coating count-rate ratio is 3:1 (for coating/substrate combinations having similar
energies) it is often helpful to use an “absorber” selected to absorb the radiation of one of the materials, usually that
of the substrate material. This absorber is usually placed manually or automatically between the surface being
measured and the detector.
3.7 Mathematical deconvolution
When using a multi-channel analyser a mathematical deconvolution of the secondary radiation spectra can be used
to extract the intensities of the characteristic radiation. This method can be used when the energies of the detected
characteristic radiations do not differ sufficiently, e.g. characteristic radiation from Au and Br. This method is
sometimes described as ‘numerical filtering’ in order to distinguish it from the filtering method (see 3.6).
3.8 Multilayer measurements
It is possible to measure more than one coating layer provided that the characteristic X-ray emissions of the inner
layers are not completely absorbed by the outer layers. In an energy dispersive system the multi-channel analyser
is set to receive two or more distinct energy bands characteristic of two or more materials.
3.9 Alloy composition thickness measurement
Certain alloys and compounds, for example Sn-Pb, can be measured simultaneously for composition and
thickness. In some cases this method can also be used under the conditions described in 3.8, e.g., Au on Pd/Ni on
a Cu alloy substrate. Since the thickness measurement of an alloy or compound is dependent upon alloy
composition, it is essential either to know or assume the composition before thickness measurement or to be able
to measure the composition.
NOTE Assumed compositions can introduce errors in thickness measurements.
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SIST EN ISO 3497:2002
ISO 3497:2000(E)
Some coatings can form alloys by interdiffusion with the substrate. The presence of such alloy layers can add to
the measurement uncertainty.
4 Apparatus
See Figures 3, 4 and 5.
1 Test specimen 4 Absorber 7 Incident X-ray beam
2 Collimator 5 X-ray generator 8 Characteristic fluorescent X-ray beam for detection and analysis
3 Detector 6 Specimen support
High voltage
Figure 3 — Schematic representation of an X-ray tube
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SIST EN ISO 3497:2002
ISO 3497:2000(E)
1 Test specimen 4 Absorber 7 Incident X-ray beam
2 Collimator 5 X-ray generator 8 Characteristic fluorescent X-ray beam for detection and analysis
3 Detector 6 Specimen support
High voltage
Figure 4 — Schematic representation of an X-ray tube with a solid specimen support
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SIST EN ISO 3497:2002
ISO 3497:2000(E)
1 Test specimen 4 Characteristic fluorescent X-ray beam for detection and analysis
2 Radioisotope and collimator 5 Absorber
3 Incident X-ray beam 6 Detector
Figure 5 — Schematic representation of a radioisotope as primary X-ray source
4.1 Primary X-ray source, being either an X-ray tube or a suitable radio isotope either of which shall be capable
of exciting the fluorescent radiation to be used for measurement.
4.2 Collimator, in the form of a precisely dimensioned aperture or apertures, which, in theory, can be of any
shape. The aperture size and shape determines the incident X-ray beam dimensions at the surface of the coating
being measured. Current commercial instruments have collimator apertures that are circular, square or rectangular.
4.3 Detector, for receiving the fluorescent radiation from the measured specimen and converting this into an
electrical signal that is passed on for evaluation. The evaluating unit is set to select one or more energy bands
characteristic of the top, intermediate and/or substrate materials.
4.4 Evaluating unit, for processing the incoming data according to its software program and thus determining the
mass per unit area or coating thickness of the test specimen.
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SIST EN ISO 3497:2002
ISO 3497:2000(E)
NOTE Fluorescent X-ray equipment suitable for measuring coating thickness in accordance with this International
Standard is available commercially. Equipment designed specifically for coating thickness measurement is of the energy
dispersive kind and usually comes with a microprocessor for converting the intensity measurement to mass per unit area or
thickness, for storing calibration data and for computing various statistical measurements.
The essential components of an X-ray fluorescence coating thickness measuring apparatus include a primary X-ray source, a
collimator, a support for the test specimen, a detector and an evaluating system. The source, collimator and detector are usually
in a geometrically-fixed relation to each other. If the atomic numbers of the coating and substrate materials are very close, it
may be necessary to introduce an absorber that will absorb the characteristic fluorescent energy of one of the materials, e.g. the
5 Factors that influence the measurement results
5.1 Counting statistics
5.1.1 The production of X-ray quanta is random with respect to time. This means that during a fixed time interval
the number of quanta emitted will not always be the same. This gives rise to the statistical error that is inherent in
all radiation measurements. In consequence, an estimate of the count rate based on a short counting period (e.g.
1 s or 2 s) can be appreciably different from an estimate based on a longer counting period, particularly if the count
rate is low. This error is independent of other sources of error, such as those arising from mistakes on the part of
the operator or from the use of inaccurate standards. To reduce the statistical error to an acceptable level, it is
necessary to use a counting interval long enough to accumulate a sufficient number of counts. When an energy
dispersive system is used, it should be recognized that a significant portion of the intended counting period may be
consumed as dead time, i.e. time during which the count-rate capacity of the system is exceeded. It is possible to
correct for dead time losses by following the manufacturer’s instructions for the particular instrumentation.
5.1.2 The standard deviation, s, of this random error closely approximates to the square root of the count rate
and the accumulation time; i.e.,
s �
X is the count-rate;
t is the accumulation time (measuring time) in seconds.
95 % of all measurements lie in the interval:
Xs��22uuX X s
5.1.3 The standard deviation of the thickness measurement is not the same as the standard deviation of the
count rate but is related to it by a function that is dependent upon the slope of the calibration curve at the point of
measurement. Most commercially available X-ray fluorescence thickness instruments display the standard
deviation in micrometres or as a percentage of mean thickness.
Using the method of deconvolution (numerical filtering) an additional contribution to the standard deviation of the
count rate comes from the mathematical algorithm.
5.2 Calibration standards
Thickness standards for calibration measurement are available. However, it cannot be guaranteed that the
accuracy of such standards is higher than 5 % (the value is lower in specific cases). Due to roughness, porosity
and d

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