ASTM E650/E650M-17

Standard Guide for Mounting Piezoelectric Acoustic Emission Sensors

SIGNIFICANCE AND USE
4.1 The methods and procedures used in mounting AE sensors can have significant effects upon the performance of those sensors. Optimum and reproducible detection of AE requires both appropriate sensor-mounting fixtures and consistent sensor-mounting procedures.
SCOPE
1.1 This document provides guidelines for mounting piezoelectric acoustic emission (AE) sensors.  
1.2 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-May-2017
• ICS: 17.140.01 - Acoustic measurements and noise abatement in general
• Technical Committee: E07 - Nondestructive Testing
• Drafting Committee: E07.04 - Acoustic Emission Method

Relations

• Replaces: ASTM E650/E650M-12 - Standard Guide for Mounting Piezoelectric Acoustic Emission Sensors
• Effective Date: 01-Jun-2017
• Refers: ASTM E1316-24 - Standard Terminology for <?Pub Dtl?>Nondestructive Examinations
• Effective Date: 01-Feb-2024
• Refers: ASTM E1316-19b - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Dec-2019
• Refers: ASTM E1316-19 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Mar-2019
• Refers: ASTM E1316-18 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Jan-2018
• Refers: ASTM E1316-17a - Standard Terminology for Nondestructive Examinations
• Effective Date: 15-Jun-2017
• Refers: ASTM E1316-17 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Feb-2017
• Refers: ASTM E1316-16a - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Aug-2016
• Refers: ASTM E1316-16 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Feb-2016
• Refers: ASTM E1316-15a - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Dec-2015
• Refers: ASTM E1316-15 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Sep-2015
• Refers: ASTM E1316-14e1 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Jun-2014
• Refers: ASTM E1316-14 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Jun-2014
• Refers: ASTM E1316-13d - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Dec-2013
• Refers: ASTM E1316-13c - Standard Terminology for Nondestructive Examinations
• Effective Date: 15-Jun-2013

Overview

ASTM E650/E650M-17 is the Standard Guide for Mounting Piezoelectric Acoustic Emission (AE) Sensors, developed by ASTM International. This guide provides comprehensive recommendations for the proper mounting of piezoelectric acoustic emission sensors to ensure optimal and reproducible sensor performance. The procedures outlined are essential for maximizing acoustic coupling, maintaining sensor stability, and achieving accurate results in nondestructive examinations using acoustic emission technology.

Key Topics

• Sensor Mounting Methods

  • Compression Mounts: Sensors are held in place by force using springs, magnets, screws, or bands. The use of a suitable couplant is highly recommended to enhance acoustic energy transfer.
  • Bonding: Sensors may be affixed to structures using adhesives. The adhesive serves as both a bonding agent and couplant, but compatibility with the sensor, structure, and environment must be ensured.

• Sensor Selection Criteria

  • Correct sensor selection is crucial based on factors such as size, sensitivity, frequency response, compatibility with structure materials, and environmental conditions.
  • For multichannel AE examinations, sensors with similar characteristics should be chosen for consistent data.

• Surface Preparation

  • Proper cleaning and mechanical preparation of contact surfaces are vital for reliable acoustic transmission. This may include removing coatings, degreasing, and treating corrosion, particularly in marine environments.

• Couplant and Bonding Agent Selection

  • The choice of couplant or bonding agent must account for the application environment (temperature, pressure, chemical composition) and ensure chemical compatibility. Optimal acoustic transmission typically requires a thin, void-free layer.

• Mounting Fixture Considerations

  • Fixtures must not introduce extraneous acoustic emissions or block valid signals. They should support the signal cable and isolate the sensor from ground loops to minimize electrical noise.

• Waveguides

  • In challenging environments, waveguides may transmit acoustic signals from the structure to remotely mounted sensors. Their use introduces boundary transitions that may affect signal characteristics.

• Verification of Sensor Response

  • Post-mounting verification of sensor response is necessary using test signals. Periodic and post-test verifications address potential changes in coupling efficiency.

Applications

The guidelines documented in ASTM E650/E650M-17 are applicable to a broad range of acoustic emission testing scenarios, particularly where small variations in sensor mounting may impact the reliability and integrity of the results. Typical application sectors include:

• Industrial Nondestructive Testing (NDT): Ensuring the integrity of pressure vessels, pipelines, storage tanks, and structural components.
• Structural Health Monitoring: Monitoring bridges, buildings, and aircraft for crack or flaw detection.
• Research and Development: Laboratory setups requiring highly reproducible and accurate AE measurements.
• Quality Assurance: Standardizing sensor mounting methods in manufacturing and maintenance operations.

Proper adherence to this guide ensures consistent, high-quality acoustic emission data essential for safety, maintenance, and validation processes.

Related Standards

• ASTM E976: Guide for Determining the Reproducibility of Acoustic Emission Sensor Response, providing additional procedures for sensor selection and comparison.
• ASTM E1316: Terminology for Nondestructive Examinations, offering a comprehensive glossary for AE and related NDT terms.

Other closely related guidelines include standards for the calibration, verification, and application of acoustic emission sensors and methods. Referencing these standards ensures a robust framework for deploying AE techniques in industrial and research contexts.

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Keywords: acoustic emission, piezoelectric sensor mounting, ASTM E650, AE sensor installation, nondestructive testing, couplant selection, sensor fixture, acoustic waveguide, sensor verification, standard guide.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E650/E650M − 17
Standard Guide for
Mounting Piezoelectric Acoustic Emission Sensors
This standard is issued under the fixed designation E650/E650M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.
A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* 3.1.3 mounting fixture—a device that holds the sensor in
place on the structure to be monitored.
1.1 This document provides guidelines for mounting piezo-
3.1.4 sensor—a detection device that transforms the particle
electric acoustic emission (AE) sensors.
motion produced by an elastic wave into an electrical signal.
1.2 Units—The values stated in either SI units or inch-
3.1.5 waveguide, acoustic—a device that couples acoustic
pound units are to be regarded separately as standard. The
energy from a structure to a remotely mounted sensor. For
values stated in each system may not be exact equivalents;
example,asolidwireorrod,coupledtoasensoratoneendand
therefore, each system shall be used independently of the other.
to the structure at the other.
Combining values from the two systems may result in non-
conformance with the standard.
3.2 Definitions:
1.3 This standard does not purport to address all of the 3.2.1 For definitions of additional terms relating to acoustic
safety concerns, if any, associated with its use. It is the emission, refer to Terminology E1316.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- 4. Significance and Use
bility of regulatory limitations prior to use.
4.1 The methods and procedures used in mounting AE
1.4 This international standard was developed in accor-
sensors can have significant effects upon the performance of
dance with internationally recognized principles on standard-
those sensors. Optimum and reproducible detection of AE
ization established in the Decision on Principles for the
requires both appropriate sensor-mounting fixtures and consis-
Development of International Standards, Guides and Recom-
tent sensor-mounting procedures.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
5. Mounting Methods
2. Referenced Documents
5.1 The purpose of the mounting method is to hold the
sensor in a fixed position on a structure and to ensure that the
2.1 ASTM Standards:
acoustic coupling between the sensor and the structure is both
E976 Guide for Determining the Reproducibility ofAcoustic
adequate and constant. Mounting methods will generally fall
Emission Sensor Response
into one of the following categories:
E1316 Terminology for Nondestructive Examinations
5.1.1 Compression Mounts—The compression mount holds
3. Terminology
the sensor in intimate contact with the surface of the structure
3.1 Definitions of Terms Specific to This Standard: through the use of force. This force is generally supplied by
3.1.1 bonding agent—a couplant that physically attaches the springs, torqued-screw threads, magnets, tape, or elastic bands.
sensor to the structure. The use of a couplant is strongly advised with a compression
mount to maximize the transmission of acoustic energy
3.1.2 couplant—a material used at the structure-to-sensor
through the sensor-structure interface.
interface to improve the transfer of acoustic energy across the
5.1.2 Bonding—The sensor may be attached directly to the
interface.
structure with a suitable adhesive. In this method, the adhesive
acts as the couplant. The adhesive must be compatible with the
This guide is under the jurisdiction of ASTM Committee E07 on Nondestruc-
structure, the sensor, the environment, and the examination
tive Testing and is the direct responsibility of Subcommittee E07.04 on Acoustic
Emission Method.
procedure.
Current edition approved June 1, 2017. Published June 2017. Originally
approved in 1985. Last previous edition approved in 2012 as E650 - 12. DOI:
6. Mounting Requirements
10.1520/E0650-17.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
6.1 Sensor Selection—The correct sensors should be chosen
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
to optimally accomplish the AE examination objective. Selec-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. tion parameters to be considered are as follows: size,
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E650/E650M − 17
sensitivity, frequency response, surface-motion response, envi- completely removable from the surface after examination. In
ronmental compatibility, background noise, source location general, the selection of the couplant is as important from an
requirements, and material properties of the structure under environmental standpoint as it is from the acoustical stand-
examination. When a multichannel acoustic-emission exami- point.
nation is being conducted, a subset of sensors with character-
6.3.2 For sensors that are primarily sensitive to particle
istics similar to each other should be selected. See Guide E976
motionperpendiculartotheirface,theviscosityofthecouplant
for methods of comparing sensor characteristics.
is not an important factor. Most liquids or greases will work as
6.1.1 If the examination objective is to include AE source
a couplant if they wet the surfaces of both the structure and the
location, sensor selection may be governed by the material
sensor. For those few sensors which are sensitive primarily to
properties of the structure and may affect subsequent sensor
motion in the plane of their face, very high-viscosity couplant
spacing due to attenuation. It may be necessary to evaluate
or a rigid bond is recommended.
attenuation effects as part of the pre-examination procedure. If
6.3.2.1 Testing has shown that in most cases, when working
performed, the attenuation data shall be retained as part of the
at frequencies below 500 kHz, most couplants will suffice.
experimental record.
However, due to potential loss of high frequency (HF) spectra
6.1.2 When a multichannel acoustic-emission examination
whenworkingabove500kHz,alowviscositycouplantorrigid
is being conducted, a subset of sensors with characteristics
bond, relative to sensor motion response, is recommended.
similar to each other should be selected. See Guide E976 for
Additionally, when spectral response above 500 kHz is needed,
methods of comparing sensor characteristics.
itisrecommendedthatFFTbeperformedtoverifyadequacyof
HF response.
6.2 Structure Preparation—The contacting surfaces should
6.3.3 The thickness of the couplant may alter the effective
be cleaned and mechanically prepared. This will enhance the
sensitivity of the sensor. The thinnest practical layer of
detection of the desired acoustic waves by assuring reliable
continuous couplant is usually the best. Care should be taken
couplingoftheacousticenergyfromthestructuretothesensor.
that there are no entrapped voids in the couplant. Unevenness,
Preparation of these surfaces must be compatible with the
suchasataperfromonesideofthesensortotheother,canalso
constructionmaterialsusedinboththesensorandthestructure.
reduce sensitivity or produce an unwanted directionality in the
Possible losses in acoustic energy transmission caused by
coatings such as paint, encapsulants, loose-mill scale, weld sensor response.
spatter, and oxides as well as losses due to surface curvature at 6.3.4 A useful method for applying a couplant is to place a
the contact area must be considered.
small amount of the material in the center of the sensor face,
6.2.1 The location of each sensor should be measured and then carefully press the sensor on to the structure surface,
marked accordingly on the structure and recorded as part of the spreading the couplant uniformly from the center to the outside
examination record. of the sensor face. Typically, this will result in a small band
6.2.2 If surface preparation requires removing paint from a (fillet) of couplant around the outside circumference of the
metalsurface,thepaintmayberemovedwithagrinderorother sensor.
mechanical means, down to bare metal. The area of paint
6.3.5 In some applications, it may be impractical to use a
removal should be slightly larger than the diameter of the
couplant because of the nature of the environment (for
sensor. If the metal surface is smooth, sandpaper may be used
example, very high temperatures or extreme cleanliness re-
to roughen the surface prior to bonding.
quirements). In these situations, a dry contact may be used,
6.2.2.1 After paint removal, the surface should be cleaned
provided sufficient mechanical force is applied to hold the
with a degreaser and wiped clean with a cloth.
sensor against the structure. The necessary contact pressure
6.2.2.2 If corrosion is present on the structure, additional
must be determined experimentally. As a rough guide, this
cleaning may include using a conditioner (mild acid) and
pressure should exceed 0.7 MPa [100 psi].
neutralizer to minimize potential corrosion beneath the sensor
6.3.6 Great care must be taken when bonding a sensor to a
after mounting.
structure. Surface deformation, that can be
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E650/E650M − 12 E650/E650M − 17
Standard Guide for
Mounting Piezoelectric Acoustic Emission Sensors
This standard is issued under the fixed designation E650/E650M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.
A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope*
1.1 This document provides guidelines for mounting piezoelectric acoustic emission (AE) sensors.
1.2 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated
in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values
from the two systems may result in non-conformance with the standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
E976 Guide for Determining the Reproducibility of Acoustic Emission Sensor Response
E1316 Terminology for Nondestructive Examinations
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 bonding agent—a couplant that physically attaches the sensor to the structure.
3.1.2 couplant—a material used at the structure-to-sensor interface to improve the transfer of acoustic energy across the
interface.
3.1.3 mounting fixture—a device that holds the sensor in place on the structure to be monitored.
3.1.4 sensor—a detection device that transforms the particle motion produced by an elastic wave into an electrical signal.
3.1.5 waveguide, acoustic—a device that couples acoustic energy from a structure to a remotely mounted sensor. For example,
a solid wire or rod, coupled to a sensor at one end and to the structure at the other.
3.2 Definitions:
3.2.1 For definitions of additional terms relating to acoustic emission, refer to Terminology E1316.
4. Significance and Use
4.1 The methods and procedures used in mounting AE sensors can have significant effects upon the performance of those
sensors. Optimum and reproducible detection of AE requires both appropriate sensor-mounting fixtures and consistent
sensor-mounting procedures.
5. Mounting Methods
5.1 The purpose of the mounting method is to hold the sensor in a fixed position on a structure and to ensure that the acoustic
coupling between the sensor and the structure is both adequate and constant. Mounting methods will generally fall into one of the
following categories:
This guide is under the jurisdiction of ASTM Committee E07 on Nondestructive Testing and is the direct responsibility of Subcommittee E07.04 on Acoustic Emission
Method.
Current edition approved June 15, 2012June 1, 2017. Published July 2012June 2017. Originally approved in 1985. Last previous edition approved in 20072012 as
E650 - 97E650 - 12.(2007). DOI: 10.1520/E0650-12.10.1520/E0650-17.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E650/E650M − 17
5.1.1 Compression Mounts—The compression mount holds the sensor in intimate contact with the surface of the structure
through the use of force. This force is generally supplied by springs, torqued-screw threads, magnets, tape, or elastic bands. The
use of a couplant is strongly advised with a compression mount to maximize the transmission of acoustic energy through the
sensor-structure interface.
5.1.2 Bonding—The sensor may be attached directly to the structure with a suitable adhesive. In this method, the adhesive acts
as the couplant. The adhesive must be compatible with the structure, the sensor, the environment, and the examination procedure.
6. Mounting Requirements
6.1 Sensor Selection—The correct sensors should be chosen to optimally accomplish the acoustic-emissionAE examination
objective. SensorSelection parameters to be considered are as follows: size, sensitivity, frequency response, surface-motion
response, and environmental and material compatibility. environmental compatibility, background noise, source location
requirements, and material properties of the structure under examination. When a multichannel acoustic-emission examination is
being conducted, a subset of sensors with characteristics similar to each other should be selected. See Guide E976 for methods of
comparing sensor characteristics.
6.1.1 If the examination objective is to include AE source location, sensor selection may be governed by the material properties
of the structure and may affect subsequent sensor spacing due to attenuation. It may be necessary to evaluate attenuation effects
as part of the pre-examination procedure. If performed, the attenuation data shall be retained as part of the experimental record.
6.1.2 When a multichannel acoustic-emission examination is being conducted, a subset of sensors with characteristics similar
to each other should be selected. See Guide E976 for methods of comparing sensor characteristics.
6.2 Structure Preparation—The contacting surfaces should be cleaned and mechanically prepared. This will enhance the
detection of the desired acoustic waves by assuring reliable coupling of the acoustic energy from the structure to the sensor.
Preparation of these surfaces must be compatible with the construction materials used in both the sensor and the structure. Possible
losses in acoustic energy transmission caused by coatings such as paint, encapsulants, loose-mill scale, weld spatter, and oxides
as well as losses due to surface curvature at the contact area must be considered.
6.2.1 The location of each sensor should be measured and marked accordingly on the structure and recorded as part of the
examination record.
6.2.2 If surface preparation requires removing paint from a metal surface, the paint may be removed with a grinder or other
mechanical means, down to bare metal. The area of paint removal should be slightly larger than the diameter of the sensor. If the
metal surface is smooth, sandpaper may be used to roughen the surface prior to bonding.
6.2.2.1 After paint removal, the surface should be cleaned with a degreaser and wiped clean with a cloth.
6.2.2.2 If corrosion is present on the structure, additional cleaning may include using a conditioner (mild acid) and neutralizer
to minimize potential corrosion beneath the sensor after mounting.
6.2.2.3 If the structure is located in a marine environment, soluble salts (e.g. chlorides, nitrates, sulfates) may still reside on
the steel surface even after cleaning. These types of salts attract moisture from the air, and may result in additional corrosion
beneath the sensor and failure of the bond. As such, a liquid soluble salt remover is recommended as an additional step in surface
preparation prior to sensor mounting.
6.3 Couplant or Bonding Agent Selection:
6.3.1 The type of couplant or bonding agent should be selected with appropriate consideration for the effects of the environment
(for example, temperature, pressure, composition of gas, or liquid environment) on the couplant and the constraints of the
application. It should be chemically compatible with the structure and not be a possible cause of corrosion. In some cases, it may
be a requirement that the couplant be completely removable from the surface after examination. In general, the selection of the
couplant is as important from an environmental standpoint as it is from the acoustical standpoint.
6.3.2 For sensors that are primarily sensitive to particle motion perpendicular to their face, the viscosity of the couplant is not
an important factor. Most liquids or greases will work as a couplant if they wet the surfaces of both the structure and the sensor.
For those few sensors which are sensitive primarily to motion in the plane of their face, very high-viscosity couplant or a rigid
bond is recommended.
6.3.2.1 Testing has shown that in most cases, when working at frequencies below 500 kHz, most couplants will suffice.
However, due to potential loss of high frequency (HF) spectra when working above 500 kHz, a low viscosity couplant or rigid
bond, relative to sensor motion response, is recommended. Additionally, when spectral response above 500 kHz is needed, it is
recommended that FFT be performed to verify adequacy of HF response.
6.3.3 The thickness of the couplant may alter the effective sensitivity of the sensor. The thinnest practical layer of continuous
couplant is usually the best. Care should be taken that there are no entrapped voids in the couplant. Unevenness, such as a taper
from one side of the sensor to the other, can also reduce sensitivity or produce an unwanted directionality in the sensor response.
6.3.4 A useful met
...