EN ISO 16809:2025

SLOVENSKI STANDARD
01-oktober-2025
Neporušitvene preiskave - Ultrazvočno merjenje debeline (ISO 16809:2025)
Non-destructive testing - Ultrasonic thickness determination (ISO 16809:2025)
Zerstörungsfreie Prüfung - Dickenbestimmung mit Ultraschall (ISO 16809:202)
Essais non destructifs - Détermination de l'épaisseur par ultrasons (ISO 16809:2025)
Ta slovenski standard je istoveten z: EN ISO 16809:2025
ICS:
19.100 Neporušitveno preskušanje Non-destructive testing
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 16809
EUROPEAN STANDARD
NORME EUROPÉENNE
June 2025
EUROPÄISCHE NORM
ICS 19.100 Supersedes EN ISO 16809:2019
English Version
Non-destructive testing - Ultrasonic thickness
determination (ISO 16809:2025)
Essais non destructifs - Détermination de l'épaisseur Zerstörungsfreie Prüfung - Dickenbestimmung mit
par ultrasons (ISO 16809:2025) Ultraschall (ISO 16809:2025)
This European Standard was approved by CEN on 14 June 2025.

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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 16809:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 16809:2025) has been prepared by Technical Committee ISO/TC 135 "Non-
destructive testing " in collaboration with Technical Committee CEN/TC 138 “Non-destructive testing”
the secretariat of which is held by AFNOR.
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 December 2025, and conflicting national standards
shall be withdrawn at the latest by December 2025.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 16809:2019.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
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, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 16809:2025 has been approved by CEN as EN ISO 16809:2025 without any modification.

International
Standard
ISO 16809
Third edition
Non-destructive testing —
2025-06
Ultrasonic thickness determination
Essais non destructifs — Détermination de l'épaisseur par
ultrasons
Reference number
ISO 16809:2025(en) © ISO 2025
ISO 16809:2025(en)
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 16809:2025(en)
Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Modes of determination . 1
5 General requirements . 3
5.1 Ultrasonic instruments .3
5.2 Probes .3
5.3 Couplant .3
5.4 Reference blocks .4
5.5 Test objects .4
5.6 Qualification of test personnel .4
6 Application of the techniques. 4
6.1 Surface condition and surface preparation .4
6.2 Technique .5
6.2.1 General .5
6.2.2 Determination during manufacture .5
6.2.3 Determination of residual wall thickness in service .6
6.3 Selection of probe.6
6.4 Selection of ultrasonic instrument .7
6.5 Special test conditions .7
6.5.1 General .7
6.5.2 Materials different from the material of the reference block.7
6.5.3 Determination at temperatures below 0 °C .7
6.5.4 Determination at elevated temperatures .8
6.5.5 Hazardous atmospheres .8
7 Instrument setting . 8
7.1 General .8
7.2 Methods of setting .8
7.2.1 General .8
7.2.2 Ultrasonic instruments with numerical display .9
7.2.3 Ultrasonic instruments with A-scan presentation .9
7.3 Checks of settings .10
8 Influence on accuracy .11
8.1 Operational conditions .11
8.1.1 Surface conditions .11
8.1.2 Temperature of the test object .11
8.1.3 Metallic coating .11
8.1.4 Non-metallic coating . 12
8.1.5 Geometry . 13
8.1.6 Material homogeneity . 13
8.2 Test equipment .14
8.2.1 Resolution .14
8.2.2 Range .14
8.3 Evaluation of accuracy. 15
8.3.1 General . 15
8.3.2 Influencing parameters . 15
8.3.3 Method of calculation . 15
9 Influence of materials .15
9.1 General . 15
9.2 Inhomogeneity . 15
9.3 Anisotropy . 15

iii
ISO 16809:2025(en)
9.4 Sound attenuation . 15
9.5 Surface conditions .16
9.5.1 General .16
9.5.2 Test surface .16
9.5.3 Reflecting surface.16
9.5.4 Corrosion and erosion .17
10 Test report . 17
10.1 General .17
10.2 General information.17
10.3 Test results .18
Annex A (informative) Corrosion in vessels and piping . 19
Annex B (informative) Instrument settings .24
Annex C (informative) Parameters influencing accuracy .27
Annex D (informative) Selection of technique for thickness determination .31
Bibliography .34

iv
ISO 16809:2025(en)
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 135, Non-destructive testing, Subcommittee
SC 3, Ultrasonic testing, in collaboration with the European Committee for Standardization (CEN) Technical
Committee CEN/TC 138, Non-destructive testing, in accordance with the Agreement on technical cooperation
between ISO and CEN (Vienna Agreement).
This third edition cancels and replaces the second edition (ISO 16809:2017), which has been technically
revised.
The main changes are as follows:
— terminology in the document has been modified, changing "measurement" to "determination";
— terminology has been aligned with ISO 16831;
— ultrasonic instruments with A-scan presentation that conform with ISO 22232-1 can be used to determine
wall thicknesses;
— all figures have been improved.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

v
International Standard ISO 16809:2025(en)
Non-destructive testing — Ultrasonic thickness determination
1 Scope
This document specifies principles for determination of the thickness of metallic and non-metallic materials
using the contact technique or immersion technique, based on measurement of the time of flight of ultrasonic
pulses only.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 5577, Non-destructive testing — Ultrasonic testing — Vocabulary
ISO 16831, Non-destructive testing — Ultrasonic testing — Characterization and verification of ultrasonic
equipment for the determination of thickness
ISO 22232-1, Non-destructive testing — Characterization and verification of ultrasonic test equipment — Part
1: Instruments
ISO 22232-2, Non-destructive testing — Characterization and verification of ultrasonic test equipment — Part
2: Probes
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5577 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Modes of determination
The thickness of a test object is determined by accurately measuring the time required for a short ultrasonic
pulse generated by a transducer to travel through the thickness of the material once, twice or several times.
The material thickness is calculated by multiplying the known sound velocity of the material of the test object
with the measured time of flight and dividing by the number of times the pulse transits the material wall.
This principle can be accomplished by applying one of the following modes (see Figure 1).
a) Mode 1: measure the time of flight from an initial excitation pulse to a first returning echo, minus a zero-
point correction to account for the thickness of the probe's wear plate or delay path and the couplant
layer (single-echo mode).
b) Mode 2: measure the time of flight from the end of a delay line to the first back wall echo (single-echo
delay line mode).
c) Mode 3: measure the time of flight between back wall echoes (multiple-echo mode).

ISO 16809:2025(en)
d) Mode 4: measure the time of flight for a pulse travelling from the transmitter to a receiver in contact
with the back wall (through-transmission mode).
a) Mode 1 b) Mode 2
c) Mode 3 d) Mode 4
Key
A transmit/receive probe D transmitter pulse indication
A transmit probe E to E back wall echoes
1 1 3
A receive probe F interface echo
ISO 16809:2025(en)
A dual-transducer probe G delay path
B test object H received pulse
C time of flight I interface
NOTE The interface echo is typically not visible for mode 1.
Figure 1 — Modes of determination
5 General requirements
5.1 Ultrasonic instruments
The ultrasonic instrument shall fulfil the requirements of ISO 16831 or ISO 22232-1, depending on the
type of instrument. The following types of ultrasonic instruments shall be used to perform thickness
determination:
a) dedicated ultrasonic instruments for the determination of thickness with only numerical display
showing the determined thickness value;
b) dedicated ultrasonic instruments for the determination of thickness with numerical display showing
the determined thickness value and A-scan presentation;
c) ultrasonic instruments not limited to thickness determination but designed primarily for the detection
of discontinuities with A-scan presentation. The operator reads the position of a signal on the time
base of the display, or this type of ultrasonic instrument can also include a gate and numerical display
showing the determined thickness value.
See 6.4 for the selection of ultrasonic instrument.
5.2 Probes
The probe(s) shall initially be in accordance with ISO 22232-2. The following types of probes shall be used
(these are generally longitudinal wave straight-beam probes):
— dual-transducer probes;
— single-transducer probes.
See 6.3 for the selection of probe.
5.3 Couplant
a) Acoustic contact between the probe(s) and the test object shall be provided, normally by application of a
fluid or gel.
b) The couplant shall not have any adverse effect on the test object, the equipment or represent a health
hazard to the operator.
c) The couplant shall be chosen to suit the surface conditions and the irregularities of the surface to ensure
adequate coupling.
d) Different coupling media can be used, but their type shall be compatible with the materials to be tested.
Examples are:
— water, possibly containing an agent, e.g. wetting, anti-freeze, corrosion inhibitor;
— contact paste;
— oil;
ISO 16809:2025(en)
— grease;
— cellulosic paste containing water.
e) The characteristics of the coupling medium shall remain constant throughout the verification, the
setting operations and the testing.
f) The coupling medium shall be suitable for the temperature range in which it will be used.
g) After testing is completed, the coupling medium shall be removed if its presence will adversely affect
subsequent operations or use of the test object.
For the use of the couplant in special test conditions, see 6.5.
5.4 Reference blocks
a) The equipment shall be set using one or more samples or reference blocks representative of the test
object, i.e. having comparable dimensions, material and structure.
b) The thicknesses of the blocks or the steps should cover the range of thickness to be determined.
c) The thickness or the sound velocity, or both, of the reference blocks shall be known.
5.5 Test objects
a) The test object shall allow for ultrasonic wave propagation.
b) There shall be free access to each individual area to be tested.
c) The surface of the area to be tested shall be free of all dirt, grease, lint, scale, welding flux and spatter,
oil or other extraneous matter that can interfere with the testing.
d) If the surface is coated, the coating shall have good adhesion to the material. Otherwise it shall be
removed.
e) When testing through coating, its thickness and sound velocity need to be known unless mode 3 is used.
For further details, see 6.1 and Clause 8.
5.6 Qualification of test personnel
a) An operator performing ultrasonic thickness determination according to this document shall have a
basic knowledge of the physics of ultrasound, and a detailed understanding and training related to
ultrasonic thickness determination.
b) In addition, the operator shall have knowledge of the product and material to be tested.
c) It is recommended that personnel is qualified in accordance with ISO 9712 or equivalent.
6 Application of the techniques
6.1 Surface condition and surface preparation
Using the pulse-echo technique means that the ultrasonic pulse needs to pass the test surface between test
object and the probe at least twice: when entering the object and when leaving it.
Therefore, a clean and even contact area with at least twice the probe's diameter is preferred. Poor contact
will result in loss of energy, distortion of signals and sound path.
a) To enable sound propagation all loose parts and non-adherent coatings shall be removed by brushing or
grinding.
ISO 16809:2025(en)
b) Attached layers, like colour coating, plating, enamels, may stay on the object, but only a few ultrasonic
instruments are able to exclude these layers from the thickness determination.
c) Very often, thickness determination needs to be done on corroded surfaces, e.g. storage tanks and
pipelines.
To increase the accuracy in this case, the test surface should be ground within an area at least two times
the probe's diameter.
This area should be cleaned from corrosion products.
When grinding, care should be taken not to reduce the thickness below the minimum acceptable value.
6.2 Technique
6.2.1 General
The task of ultrasonic thickness determination can be separated into two application areas:
— determination during manufacture;
— determination of residual wall thickness in service.
Each area has its own special conditions which require special techniques.
Using knowledge of the material, geometry and approximate thickness to be determined and the required
accuracy, the most suitable test equipment and mode shall be selected as follows (Annex D gives guidance):
a) depending on the thickness and the material, frequencies from 100 kHz with through-transmission
technique on highly attenuative materials up to 50 MHz on thin metal sheets shall be used;
b) if dual-transducer probes are used, then compensation for V-path error is required;
c) on curved test objects, the diameter of the probe contact area shall be significantly smaller than the
diameter of the test object.
The accuracy of the thickness determination depends on how accurate the time of flight can be measured,
on the measurement mode for the time difference (zero crossing, flank-to-flank, peak-to-peak), on the mode
of determination (with multiple echoes, mode 3, the accuracy is higher than with modes 1 and 2), and on the
frequencies which can be used (higher frequencies provide higher accuracy than lower frequencies because
of the more accurate time measurement).
d) Ultrasonic thickness determination is often required over an area of the test object. Where this is the
case, consideration shall be given to the spacing between testing locations.
e) Such spacing shall be even and the use of a grid is recommended.
f) The grid size shall be selected to give a balance between the confidence in the results, detection of local
thickness variations and the work content involved.
To determine the thickness ultrasonically means measuring the time of flight and then calculating the
thickness assuming a constant sound velocity (see Clause 7).
If the sound velocity is not constant within the path the ultrasonic pulse has travelled, the accuracy of the
determination will be severely affected.
6.2.2 Determination during manufacture
6.2.2.1 Modes 1, 2 and 3
a) Where the pulse-echo mode is used, the flow charts in Figures D.1 and D.2 give guidance on the selection
of the best technique and equipment.

ISO 16809:2025(en)
b) Thickness determination on clean parallel surfaces may be carried out with simple ultrasonic
instruments for thickness determination with numerical display [type 5.1 a)].
c) On composite materials which generate echoes in addition to the back wall echo, it is recommended that
ultrasonic instruments with A-scan presentation [type 5.1 b) or 5.1 c)] be used to select the correct echo
for the thickness determination.
6.2.2.2 Mode 4
If the material is highly attenuative and large thicknesses need to be tested, no pulse-echo technique can be
used, i.e. only through-transmission (mode 4) is applicable.
a) Two probes on opposite sides of the test object shall then be used.
b) The ultrasonic instrument therefore shall allow for operation with separate transmitter and receiver
(TR mode).
c) In most cases, the frequency shall be lower than 1 MHz.
d) Special low-frequency ultrasonic instruments from type c) in 5.1 with low-frequency probes shall be used.
6.2.3 Determination of residual wall thickness in service
During in-service testing, thickness determinations need to be taken on materials that are subject to
corrosion or erosion. The surfaces can be rough and contain pitting or other imperfections (see Annex A)
which are areas of low reflectivity.
a) For these applications, the use of dual-transducer probes and ultrasonic instruments with A-scan
presentation is recommended.
b) The sensitivity shall be set manually to detect the poor reflecting areas.
c) Where it is necessary to take a lot of thickness determinations, the readings shall be values with the
information on the location of the test position. Data logging software can therefore be applied.
d) With in-service testing, the environmental conditions are very important. Equipment can be needed
which can withstand high temperatures and harsh environments or has special electrical shielding.
The flowcharts in Figures D.3 and D.4 give guidance on thickness determination in-service.
6.3 Selection of probe
Having chosen a suitable testing technique according to 6.2, i.e. a general decision for a probe type (single-
or dual-transducer) has been made, there are other parameters that need to be considered when matching
the probe to the test conditions.
Wide-band probes offer a shorter pulse than narrow-band probes, thus giving a suited flank or peak for the
time-of-flight measurement, giving a better resolution when testing thin sheets or coatings.
Additionally, a wide frequency band always gives a stable echo even when attenuating materials need to
be tested.
a) Probe size and frequency shall be chosen to cover the thickness range by a narrow sound beam to get an
echo from a well-defined area.
b) For dual-transducer probes the focal range shall cover the expected thickness range.
c) When determining small thicknesses:
1) a delay path shall be used;

ISO 16809:2025(en)
2) a dual-transducer probe with small focal distance may be used.
d) The material of the delay path shall be chosen to generate a suitable interface echo. Using the same
material as the test object does not generate an interface echo.
When the material of the delay path has a lower acoustic impedance than the material to be tested, e. g.
a plastics delay line on metals or when using immersion, there is a phase shift of the interface echo.
This shall be taken into account in order to obtain correct results. Some ultrasonic instruments do this
correction automatically.
e) When testing on hot surfaces, the delay path shall act as a thermal barrier.
The material chosen for the delay path shall withstand the temperatures of the test object. The influence
of the temperature on the acoustical properties of the delay path needs to be known (drift of sound
attenuation and velocity).
Data sheets of the probe manufacturers show the range of temperatures a probe is suitable for and the
time it can be used on those temperatures.
6.4 Selection of ultrasonic instrument
Selection of ultrasonic instruments of type 5.1 a), b) or c) shall be made as follows:
a) ultrasonic instruments of type 5.1 a) shall be used for modes 1, 2 and 3 only (see Clause 4) and may be
preset by the manufacturer to work only in one of the modes 1, 2 or 3 (see Clause 4) and shall satisfy the
conditions given in 6.2.2.1 or 6.2.3 depending on the application area (manufacture or in service).
b) ultrasonic instruments of type 5.1 b) shall be used for modes 1, 2 and 3 only (see Clause 4) and shall
satisfy the conditions given in 6.2.2.1 or 6.2.3 depending on the application area (manufacture or in
service);
c) ultrasonic instruments of type 5.1 c) may be used for all modes 1 to 4 (see Clause 4) and shall satisfy the
conditions given in 6.2.2 or 6.2.3 depending on the application area (manufacture or in service).
See also Annex D.
6.5 Special test conditions
6.5.1 General
a) Attention is drawn that legislative procedures governing the safe use of chemicals and electrical
equipment apply.
b) Where there is a requirement for high-accuracy determination, the standard or reference blocks used
shall be at the same temperature as the test object.
6.5.2 Materials different from the material of the reference block
The use of reference blocks of material different from the test object is not recommended, see Tables B.1 and B.2.
6.5.3 Determination at temperatures below 0 °C
a) For tests below 0 °C, the couplant chosen shall retain its acoustic characteristics and have a freezing
point below the test temperature.
b) Most probes are rated for use between −20 °C and +60 °C. At temperatures below −20 °C, specially
designed probes can be required and contact time shall be limited as recommended by the manufacturer.

ISO 16809:2025(en)
6.5.4 Determination at elevated temperatures
a) For tests above 60 °C, a high-temperature probe is required and the couplant shall be designed for use at
the test temperature.
b) It is also recommended that, when using equipment with A-scan representation, it should have a “freeze”
mode to allow the operator to assess the signal response.
c) The probe contact time shall be limited to the minimum time necessary to achieve a test result as
recommended by the manufacturer.
6.5.5 Hazardous atmospheres
a) In the determination of thickness in hazardous atmospheres, applicable safety regulations and
standards can exist.
b) In explosive atmospheres, the probe, cable and equipment combination shall be classified as intrinsically
safe and relevant safety certification and documentation shall be checked and completed prior to use.
NOTE Typically standard ultrasonic equipment is not intrinsically safe.
c) In corrosive atmospheres, the couplant shall not react adversely with the environment and shall retain
its acoustic properties.
7 Instrument setting
7.1 General
It should be noted that this clause covers only the setting of the ultrasonic instrument. The verification of
the equipment characteristics is not considered but can be performed according to the design specification.
Ultrasonic instruments do not measure thickness; they measure time of flight. The thickness is calculated
by the application of a factor which is the sound velocity of the material according to Formula (1).
dv=×tm/ (1)
where
d is the determined thickness;
v is the sound velocity of the material;
t is the measured time;
m is the number of transits (single thickness) through the test object (see Figure 1).
NOTE For mode 1 and mode 2 m is equal to 2, for mode 3 m is a multiple of 2, for mode 4 m is equal to 1.
a) The instrument setting shall be carried out with the same equipment (ultrasonic instrument, probe,
cable) as that which will be used for testing.
b) The instrument setting shall be carried out in accordance with the manufacturer’s instructions or other
valid standards or procedures.
7.2 Methods of setting
7.2.1 General
a) The method for setting the ultrasonic instrument shall suit the mode of determination and the
equipment and probe in use.
ISO 16809:2025(en)
b) The setting shall be carried out under comparable operating conditions as those of the thickness
determination.
Annex B gives guidance on the selection of methods for setting ultrasonic instruments.
Differences exist between the setting of an ultrasonic instrument with numerical display [types 5.1 a) and
b)] and an ultrasonic instrument with A-scan presentation [type 5.1 c)].
7.2.2 Ultrasonic instruments with numerical display
If ultrasonic instruments of type 5.1 c) are used with a gate and numerical display, then they can also be
used according to this subclause.
Many ultrasonic instruments with numerical display can be used in modes 1, 2 and 3.
The setting of the ultrasonic instrument may be achieved in either of two ways:
a) by adjusting the displayed reading such that it agrees with the known dimensions of the reference blocks;
b) adjusting or setting the material velocity on the ultrasonic instrument to agree with the known velocity
of the test object.
7.2.3 Ultrasonic instruments with A-scan presentation
Refer to ISO 16811 for information regarding the time-base setting of an ultrasonic instrument with A-scan
presentation.
If ultrasonic instruments of type 5.1 c) are used with a gate and numerical display, then they can also be
used according to 7.2.2.
When using mode 1 with an ultrasonic instrument with A-scan presentation.
a) The horizontal time base shall be set such that the transmission pulse indication is displayed at or
before the zero point and the first back wall echo from the reference block is displayed at a position on
the screen corresponding to the known thickness, for different thicknesses of the reference block(s).
b) If the ultrasonic instrument has a numerical display, this may also be used.
When using mode 2 with an ultrasonic instrument with A-scan presentation:
c) Set the transmission pulse indication such that it is off the screen and the interface echo is at the zero
point on the graticule.
d) Then set the first back wall echo to be at the mark relating to the known thickness of the reference block.
When using mode 3 with an ultrasonic instrument with A-scan presentation:
e) Set the first back-wall echo to be at the mark relating to the known thickness of the reference block.
th
f) Then set the n back wall echo to be at the mark relating to n times the known thickness of the reference
block, with n being the number of subsequent backwall echoes.
g) When determining the thickness of the test object, the zero point
...