ISO 24543:2022

INTERNATIONAL ISO
STANDARD 24543
First edition
2022-09
Non-destructive testing — Acoustic
emission testing — Verification of
the receiving sensitivity spectra
of piezoelectric acoustic emission
sensors
Essais non destructifs — Contrôle par émission acoustique —
Vérification des spectres de sensibilité de réception des capteurs
d’émission acoustique piézoélectriques
Reference number
ISO 24543:2022(E)
© ISO 2022

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ISO 24543:2022(E)
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© ISO 2022
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Published in Switzerland
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ISO 24543:2022(E)
Contents Page
Foreword .v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms.3
5 Overview . 4
5.1 Face-to-face setup — Block diagram . 4
5.2 Laser vibrometer setup — Block diagram . 5
6 General requirements related to hardware . 6
6.1 General . 6
6.2 Requirements related to the function generator (FG) . 6
6.3 Requirements related to the transmitter . 7
6.4 Requirements related to the coupling agent between transmitter and sensor
under test . 8
6.5 Requirements related to the sensor-to-transmitter fixing tool . 8
6.5.1 General . 8
6.5.2 Requirements . 8
6.6 Requirements related to the sensor under test (SUT) . 9
6.6.1 General . 9
6.6.2 Pyroelectric effect . 9
6.6.3 Integrated pre-amplifier . 10
6.6.4 Influence of the pre-amplifier input impedance . 10
6.6.5 Requirements for a list of sensors under test . 10
6.7 Requirements related to the signal cable from sensor to transient recorder. 10
6.7.1 General . 10
6.7.2 Requirement . 10
6.8 Requirements related to the signal cable from the function generator to the
transmitter and to the transient recorder . 10
6.9 Requirements related to the transient recorder for measuring U and U . 11
S F
6.9.1 General . 11
6.9.2 Input impedance . 11
6.9.3 Range, resolution, accuracy, sampling rate and buffer length . 11
6.9.4 Bandwidth .12
6.9.5 Trigger settings .12
6.9.6 Verification — Calibration .12
7 Determination of the receiving sensitivity spectra .12
7.1 General .12
7.2 Formulae for the determination of receiving sensitivity spectra R and R .12
D V
7.3 Relevant spectra for sensor sensitivity verification . 13
7.4 Procedure for sensor sensitivity verification . 14
7.4.1 Preparation . 14
7.4.2 Cable connections for the face-to-face setup . 15
7.4.3 Settings of the function generator in the face-to-face setup .15
7.4.4 Setting of the transient recorder . 16
7.4.5 Trial measurement . 17
7.4.6 Initial crosstalk test . 18
7.4.7 Capturing data of the sensor under test — Stimulation pulse U , sensor
F
response U . 18
S
7.4.8 Calculating and presenting receiving sensitivity spectra . 19
7.4.9 Sensor verification report . 20
7.5 Reproducibility of sensitivity spectra . 21
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ISO 24543:2022(E)
7.5.1 Sensor-to-transmitter coupling . 21
7.5.2 Influence of temperature . 21
7.5.3 Change of the transmitter . 21
8 Determination of the transmitting sensitivity spectra.22
8.1 Formula for the determination of the transmitting displacement sensitivity .22
8.2 Requirements related to the scanning laser vibrometer . 23
8.3 Procedure for the determination of transmitting sensitivities T . 24
D
8.3.1 Preparation . 24
8.3.2 Cable connections for the laser vibrometer setup. 24
8.3.3 Function generator settings for the laser vibrometer setup . 24
8.3.4 Capturing laser vibrometer data . 25
8.3.5 Calculating the displacement results . 25
8.4 After completion of the motion measurement . 26
8.5 Criteria to sort out unsuitable transmitters . 26
8.6 Calibration of the laser vibrometer .28
8.7 Detection of a drift of a transmitting sensitivity .28
Annex A (informative) Examples of templates .30
Annex B (informative) Examples of equipment .32
Annex C (informative) Verification methods for piezoelectric acoustic emission sensors .34
Annex D (informative) Additional information concerning receiving sensitivity
determination .38
Annex E (informative) Additional information concerning transmitting sensitivity
determination .51
Annex F (informative) Adapting R /R to the acoustic impedances of the used materials .58
V D
Bibliography .60
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ISO 24543:2022(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
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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 9, Acoustic emission testing.
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.
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ISO 24543:2022(E)
Introduction
The proposed method of determining the receiving sensitivity spectra of a piezoelectric acoustic
emission sensor is based on a setup where the face of the sensor under test is directly coupled via a
thin layer of coupling agent to the active face of a piezoelectric transmitter. The transmitter, usually an
ultrasonic probe, stimulates the sensor under test by a particle displacement pulse in normal direction
to the sensor’s face. The displacement pulse is measured by a vibrometer at a number of positions on the
active area of the transmitter. This allows determining the transmitting sensitivity of the transmitter
in absolute units of nm/V and the receiving sensitivity of the sensor under test in absolute units of V/
nm.
The aim is to establish uniformity of acoustic emission testing, to form a basis for data correlation,
and to provide a basis for the uniform interpretation of results obtained by different acoustic emission
testing organizations at different times. For more information about the verification methods for
piezoelectric sensors, see Annex C.
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INTERNATIONAL STANDARD ISO 24543:2022(E)
Non-destructive testing — Acoustic emission testing
— Verification of the receiving sensitivity spectra of
piezoelectric acoustic emission sensors
1 Scope
This document specifies a method for the determination of the receiving sensitivity spectra of a
piezoelectric acoustic emission sensor, in absolute units of volts output per motion input, whereby
the motion can be particle displacement (e.g. in nanometres) or particle velocity (e.g. in millimetres
per second) over a frequency range used for acoustic emission testing, from 20 kHz to about 1,5 MHz,
whereby the sensor is stimulated by a motion pulse in normal direction to the sensor’s face from a
directly coupled piezoelectric transmitter.
This document also specifies a method for the determination of the transmitting sensitivity spectrum
of a piezoelectric transmitter in absolute units, for example, in nanometres output per volt input, by
measuring both the particle displacement pulse over the transmitter’s active face and the transmitter’s
input voltage spectrum, using a scanning laser vibrometer.
This document does not include the known cancellation effects on a sensor’s response, when the angle
of incidence differs from normal (90°) or when the length of the wave passing across the sensor’s
sensitive face is shorter than about 10 times the dimension of the sensor’s sensitive face.
This document does not specify a method to measure the influence of different materials on a sensor’s
sensitivity, but this effect is addressed in Annex F.
NOTE The methods described in this document can be considered for use with other than piezoelectric
sensors, which detect motion at a flat face and work in the same frequency range.
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 12716, Non-destructive testing — Acoustic emission inspection — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 12716 and the following 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/
3.1
transmitter
TM
piezoelectric device that converts an electrical signal to particle motion or pressure
Note 1 to entry: A single-letter TM identifier (TM-id A to Z) may be appended to identify a certain unit of
transmitter.
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ISO 24543:2022(E)
3.2
sensor under test
SUT
piezoelectric acoustic emission sensor whose receiving sensitivity (3.8, 3.9) spectra are verified
Note 1 to entry: A double-digit SUT identifier (SUT-id 00 to 99) may be appended to identify a type of SUT.
3.3
function generator
FG
electronic device for generating the stimulation pulse for the transmitter (3.1)
3.4
transient recorder
TRA
electronic device for waveform capture at two or more signal inputs with trigger input, pre-trigger
capability and personal computer interface
3.5
scanning laser vibrometer
LVM
instrument for non-contacting measurement of particle motion in absolute units of nanometres at a
number of positions on a surface in normal direction
3.6
face-to-face setup
arrangement where the active face of a transmitter (3.1) is directly coupled to the sensitive face of a
sensor under test (3.2) for a reproducible stimulation by an electrical pulse
3.7
laser vibrometer setup
LVM setup
arrangement where a scanning laser vibrometer (3.5) is used to measure the particle displacement pulse
at multiple positions at the free active face of a transmitter (3.1)
3.8
receiving displacement sensitivity
R
D
output voltage spectrum of a sensor in dB minus the particle displacement input spectrum in dB
Note 1 to entry: In this document, 0 dB of particle displacement sensitivity (R ) refers to 1 V/nm,
D
Note 2 to entry: When the term "sensitivity" is clearly related to a sensor under test (3.2), the word "receiving"
can be omitted.
3.9
receiving velocity sensitivity
R
V
output voltage spectrum of a sensor in dB minus the particle velocity input spectrum in dB
Note 1 to entry: In this document, 0 dB of particle velocity sensitivity (R ) refers to 1 Vs/mm.
V
Note 2 to entry: When the term "sensitivity" is clearly related to a sensor under test (3.2), the word "receiving"
can be omitted.
3.10
transmitting displacement sensitivity
T
D
output displacement spectrum of a transmitter (3.1) in dB minus its input voltage spectrum in dB
Note 1 to entry: In this document, 0 dB of particle displacement sensitivity (T ) refers to 1 nm/V.
D
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ISO 24543:2022(E)
Note 2 to entry: When the term "sensitivity" is clearly related to a transmitter, the word "transmitting" can be
omitted.
3.11
transmitting velocity sensitivity
T
V
output velocity spectrum of a transmitter (3.1) in dB minus its input voltage spectrum in dB
Note 1 to entry: In this document, 0 dB of particle velocity sensitivity (T ) refers to 1 mm/Vs.
V
Note 2 to entry: When the term "sensitivity" is clearly related to a transmitter, the word "transmitting" can be
omitted.
3.12
Han2SQ
designation of a specific time window function applied to the input of the fast Fourier transform on the
response of an acoustic emission sensor or of a laser vibrometer to a displacement pulse
Note 1 to entry: See D.2.3.
4 Symbols and abbreviated terms
D displacement signal measured by LVM and converted to a spectrum with 0 dB referring to 1 pm
peak; “D” may be appended by a TM-id (A to Z), a ring-id (1 to 5), and a window-id, see W7 below
FFT fast Fourier transform, a method to convert a time-series signal into a frequency spectrum
MS/s mega samples per second; “1 MS” means "1 million samples"
20
NOTE: If a quantity of memory is given in "MS", "1 MS" usually means "2 " (1 048 576) samples.
N number of a ring of measurement positions in range 1 to 5, see 8.2
R
N largest ring number N of measurement positions (see Figure 6) covering the sensitive face of
RL R
a type of SUT, for correct T selection, recorded in Table A.2
D
r radius of ring number N in mm, see 8.2
R R
R signal-to-stimulation ratio spectrum in dB, see Formula (4); the recommended naming of a
SS
specific R data file begins with "S", followed by the SUT-id (00 to 99), the TM-id (A to Z) and
SS
a window-id, see W7 below
R drift detection sensitivity spectrum of drift detection sensor 1, for the verification of a trans-
VDD1
mitting sensitivity drift, see 8.7 c) 1)
R drift detection sensitivity spectrum of drift detection sensor 2, for the verification of a trans-
VDD2
mitting sensitivity drift, see 8.7 c) 1)
R drift reference sensitivity spectrum of drift detection sensor 1, determined with a transmitter’s
VDR1
sensitivity determination according to 8.7 a)
R drift reference sensitivity spectrum of drift detection sensor 2, determined with a transmitter’s
VDR2
sensitivity determination according to 8.7 a)
R spectrum difference R minus R of drift detection sensor 1, see 8.7 c) 2)
VΔ1 VDD1 VDR1
R spectrum difference R minus R of drift detection sensor 2, see 8.7 c) 2)
VΔ2 VDD2 VDR2
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ISO 24543:2022(E)
U transmitter voltage in face-to-face setup, stimulated by a function generator and measured by
F
a transient recorder in the time domain, then transformed into the spectrum F(U ) in dB, with
F
0 dB referring to a sine wave of 1 mV peak
U transmitter voltage in LVM setup, stimulated by a function generator and measured by the
L
LVM in the time domain, then transformed into the spectrum F(U ) in dB, with 0 dB referring
L
to a sine wave of 1 mV peak
U sensor output voltage, also called “sensor response”, measured by a transient recorder in the
S
time domain, then converted into the spectrum F(U ) in dB, with 0 dB referring to a sine wave
S
of 1 mV peak
U average of 4 or 6 responses U from one SUT, stimulated by 4 or 6 transmitters, in per cent of
SAV% S
its maximum peak-to-peak voltage, see Figure 7
U deviation of the response U from U , with U in per cent of its maximum peak-to-peak
SΔ% S SAV% S
voltage, see Figure 7
F(D) FFT of the time signal D
F(U ) FFT of the time signal U
F F
F(U ) FFT of the time signal U
L L
F(U ) FFT of the time signal U
S S
W5 identifier for a 4 µs main-pulse time window
W7 identifier for a 50 µs time window
W8 identifier for a 100 µs time window
W9 identifier for a 200 µs time window
5 Overview
5.1 Face-to-face setup — Block diagram
The block diagram of the face-to-face setup is shown in Figure 1 a). Numerical keys identify the blocks
and alphabetical keys the interfaces. In this clause, the keys of Figure 1 are referenced in brackets.
The function generator (1) delivers the stimulation pulse U at the signal output (A) with a constant
F
repetition rate.
The signal U (A) is connected to the input (D) of transmitter (2), and to the input channel B (J) of
F
transient recorder (4). The electrical pulse stimulates a motion pulse at the transmitter’s active face
(E). This face is acoustically coupled via a thin layer of coupling agent (F) to the sensitive face (G) of the
sensor under test (3). The sensor’s signal output (H) delivers the sensor response U , which is connected
S
to the input channel A (I) of transient recorder (4). The transient recorder signal capture is triggered
at (K) by trigger output signal “Sync” (B) of function generator (1). The transient recorder (4) is under
control of a personal computer (5) via interfaces (L) and (M).
The data captured of each trigger are read out via (L) and (M) by personal computer (5) and shown at
the PC display in the time interval of the stimulation pulse, usually 200 milliseconds.
Stimulation pulse U (A) is shown in Figure D.1.
F
Examples of sensor responses U (H) of three types of sensors are shown in Figure D.6. to Figure D.8.
S
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ISO 24543:2022(E)
Not shown in Figure 1 is the fixture needed to align the centres of sensor and transmitter and to apply
a force on the interface (E–F–G). The force required depends on properties of the coupling agent and on
other forces that can apply, e.g. from the cable. A force of 10 N is recommended.
The operator may manipulate the fixture in order to see, if the coupling is stable or can be improved.
If satisfied with the reproducibility of the signal, the operator stops the capture repetition and stores
the latest acquired signal into a properly named file.
a) Face-to-face setup b) Laser vibrometer setup
Key
1 function generator (FG) with signal output key F coupling agent at the TM-to-SUT interface, also called
A, sync output key B and trigger input key C "couplant", see ISO 12716:2001, 2.15
2 transmitter with pulse input key D and G SUT input motion at its sensitive face, from key E in
displacement output at its active face key E face-to-face setup
3 sensor under test (SUT) with displacement H SUT output signal U to key I in face-to-face setup
S
sensitive input key G and response voltage
output key H
4 transient recorder (TRA) with channel A input I TRA input channel A, measures U from key H
S
key I, channel B input key J, trigger input key K,
and PC interface key L
5 personal computer (PC) with interface key M J TRA input channel B, measures U from key A
F
6 laser scan positioning unit for 21 positions at the K TRA trigger input from key B
active transmitter face key E
7 scanning laser vibrometer (LVM) with optical L TRA to PC interface, TRA-side
input key N, reference voltage input key O, and
trigger output key P
A FG output signal U in face-to-face setup, U in M PC in-/output from/to key L in face-to-face setup or
F L
LVM setup, the stimulation pulse key Q in LVM setup
B FG trigger output “Sync” to key K, open in LVM N LVM laser beam sequentially positioned by key 6 to
...