ASTM E1065/E1065M-20

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: E1065/E1065M − 20
Standard Practice for
Evaluating Characteristics of Ultrasonic Search Units
ThisstandardisissuedunderthefixeddesignationE1065/E1065M;thenumberimmediatelyfollowingthedesignationindicatestheyear
of original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.
A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.1 This practice covers measurement procedures for evalu-
1.7 This international standard was developed in accor-
ating certain characteristics of ultrasonic search units (also
dance with internationally recognized principles on standard-
known as “probes”) that are used with ultrasonic testing
ization established in the Decision on Principles for the
instrumentation. This practice describes means for obtaining
Development of International Standards, Guides and Recom-
performance data that may be used to define the acoustic and
mendations issued by the World Trade Organization Technical
electric responses of ultrasonic search units.
Barriers to Trade (TBT) Committee.
1.2 The procedures are designed to measure search units as
individualcomponents(separatefromtheultrasonictestinstru-
2. Referenced Documents
ment) using commercial search unit characterization systems
2.1 ASTM Standards:
or using laboratory instruments such as signal generators,
E1316Terminology for Nondestructive Examinations
pulsers, amplifiers, digitizers, oscilloscopes, and waveform
2.2 ISO Standards:
analyzers.
ISO 10375:1997 Non-destructive Testing—Ultrasonic
1.3 The procedures are applicable to manufacturing accep-
Inspection—Characterization of Search Unit and Sound
tance and incoming inspection of new search units or to
Field
periodic performance evaluation of search units throughout
2.3 Other Document:
their service life.
Standard Methods for Testing Single Element Pulse-Echo
1.4 The procedures in AnnexA1 – AnnexA6 are generally
Ultrasonic Transducers
applicabletoultrasonicsearchunitsoperatingwithinthe0.4to
10 MHz range. Annex A7 is applicable to higher frequency
3. Terminology
immersion search unit evaluation. Annex A8 describes a
3.1 Definitions—For definitions of terms used in this
practice for measuring sound beam profiles in metals from
practice, see Terminology E1316.
contact straight-beam search units. Additional Annexes, such
3.2 Definitions of Terms Specific to This Standard:
as sound beam profiling for angle-beam search units in metal
3.2.1 aperture, n—the dimension(s) of the active area of the
and alternate means for search unit characterization, will be
piezoelectric element of the search unit as established by
added when developed.
experimentation.
1.5 Units—The values stated in either SI units or inch-
3.2.2 bandwidth (BW), n—that portion of the frequency
pound units are to be regarded separately as standard. The
response that falls within given limits.
values stated in each system are not necessarily exact equiva-
3.2.2.1 Discussion—In this text, the limits used are the
lents; therefore, to ensure conformance with the standard, each
-6dB level, as measured from the peak of the frequency
system shall be used independently of the other, and values
response. The equation used for BW is:
from the two systems shall not be combined.
BW 5 f 2 f /f 3100 (1)
~ !
1.6 This standard does not purport to address all of the u 1 c
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
This practice is under the jurisdiction of ASTM Committee E07 on Nonde- the ASTM website.
structive Testing and is the direct responsibility of Subcommittee E07.06 on Available from International Organization for Standardization (ISO), ISO
Ultrasonic Method. Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier,
Current edition approved Jan. 15, 2020. Published February 2020. Originally Geneva, Switzerland, http://www.iso.org.
approved in 1985. Last previous edition approved in 2014 as E1065/E1065M–14. Available from the American Institute of Ultrasonics in Medicine, 14750
DOI: 10.1520/E1065_E1065M-20. Sweitzer Lane, Suite 100, Laurel, MD 20707-5906.
*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
E1065/E1065M − 20
where: contact search units. Annex A2 describes the procedure for
obtaining bandwidth characteristics.
f = upper frequency,
u
4.1.2 Relative Pulse-Echo Sensitivity (S )—The relative
f = lower frequency, and
rel
f = center frequency. pulse-echo sensitivity may be obtained from the frequency
c
response data obtained using the sinusoidal burst procedure
Bandwidth is expressed as a percentage.
described in Annex A1. The value is obtained from the
3.2.3 center frequency (f ), n—the frequency value calcu-
c
relationship of the amplitude of the voltage applied to the
lated to be at the center of the bandwidth limits.
searchunitandtheamplitudeofthepulse-echosignalreceived
3.2.4 depth of field (F ), n—as measured on the on-axis
from a specified target. AnnexA3 describes the procedure for
D
profileofafocusedsearchunit,thatportionofthesoundbeam
obtaining pulse-echo sensitivity.
that falls within given limits.
NOTE 1—Values for applied and received power, from which insertion
3.2.5 focal length (F ), n—for focused search units, the
L loss might be determined, are not covered with procedures described in
distance from the lens to the focal point. this practice.
3.2.6 focal point (F ), n—for focused search units, the point 4.1.3 Time Response—The time response provides a means
p
along the acoustic axis of the beam in water at which the peak for describing the radio frequency (rf) response of the wave-
form. A shock excitation, pulse-echo procedure is used to
(maximum) pulse-echo amplitude response is recorded from a
ball target reflector. obtain the response. The time or waveform responses are
recorded from specific targets that are chosen for the type of
3.2.6.1 Discussion—This is also referred to as Y
search unit under evaluation (for example, immersion, contact
3.2.7 frequency response, n—the pulse-echo response of the
straight beam, or contact angle beam). AnnexA4 describes the
search unit measured as a function of frequency. (This term is
procedures for measuring time response.
also referred to as frequency spectrum.)
4.1.4 Electrical Impedance:
3.2.8 nominal frequency (f ), n—the frequency stated on
nom
4.1.4.1 Complex Electrical Impedance—The complex elec-
the label supplied by the manufacturer.
trical impedance may be obtained with commercial impedance
3.2.9 on-axis profile, n—a sequence of measurements made
measuring instrumentation, and these measurements may be
along the acoustic axis of the beam of the search unit.
used to provide the magnitude and phase of the impedance of
3.2.10 peak frequency (f ), n—the frequency value at the the search unit over the operating frequency range of the unit.
p
These measurements are generally made under laboratory
maximum amplitude of the frequency response.
conditions with minimum cable lengths or external accessories
3.2.11 pulse duration, n—the length of the electrical im-
and in accordance with the instructions of the instrument
pulse or sinusoidal burst used to excite the search unit as
manufacturer. The value of the magnitude of the complex
expressed in time or number of cycles.
electrical impedance may also be obtained using values re-
3.2.12 pulse echo sensitivity, n—a measurement that com-
corded from the sinusoidal burst techniques as outlined in
pares the amplitude of the applied voltage with the amplitude
Annex A5.
of the pulse-echo voltage recorded from a specified target.
4.1.4.2 d-c Resistance—Thed-cresistanceofthesearchunit
3.2.13 shock excitation, n—a short electrical impulse that is
may provide information regarding the electrical tuning ele-
applied to the search unit.
ments.Measurementsaremadeacrosstheterminalsoftheunit.
3.2.13.1 Discussion—The impulse is typically a negative-
4.1.5 Sound Field Measurements—The objective of these
going voltage spike of fast rise time and short duration.
measurements is to establish parameters such as the on-axis
Typically generated by spike or square wave pulsers.
and transverse sound beam profiles for immersion flat and
focused search units.
3.2.14 transverse profile, n—sequence of measurements
4.1.5.1 Annex A6 and Annex A8 of this practice describe
made along a line perpendicular to the acoustic axis of the
waysformakingsoundfieldmeasurementsforbothimmersion
beam of the search unit.
flatandfocusedsearchunitsinwaterandcontactstraight-beam
3.2.15 sinusoidal burst, n—also known as tone burst.
search units in metal. The literature discusses several ways for
3.2.16 waveform duration, n—the time interval or duration
making these measurements, but the techniques described are
over which the unrectified signal or echo from a specified
relatively simple and easily performed.
target exceeds a selected amplitude level as related to the
4.1.5.2 Means are recommended for making measurements
maximum amplitude of the signal or echo (for example,−20
in an immersion tank, thereby allowing either pulse-echo (ball
or−40 dB).
target) or hydrophone receiver techniques to be followed. The
goal is to provide measurements to evaluate the characteristics
4. Summary of Practice
of search units or to identify changes that may occur as a
4.1 The acoustic and electrical characteristics which can be
function of time or use, or both.
describedfromthedataobtainedbyproceduresoutlinedinthis
4.1.5.3 None of the measurements of sound beam patterns
practice are described as follows:
areintendedtodefinelimitsofperformance.Theyaredesigned
4.1.1 Frequency Response—Thefrequencyresponsemaybe
to provide a common means for making measurements that
obtained from one of two procedures: (a) shock excitation and
may be used to define the initial and inservice performance.
(b) sinusoidal burst. Annex A1 describes procedures for
obtaining frequency response for immersion and zero-degree NOTE 2—No procedure is given for measuring sound beam profile
E1065/E1065M − 20
characteristics for angle-beam search units. Several potential approaches
5.6 While these procedures relate to many of the significant
are being considered, but have not yet gained subcommittee agreement
parameters, others that may be important in specific applica-
(1).
tions may not be treated. These might include power handling
NOTE 3—Frequency Response Displays. The frequency responses in
capability,breakdownvoltage,wearpropertiesofcontactunits,
Fig. 1 and Fig. 2 and throughout the text are displayed as a linear
amplitude (not logarithmic) response as a function of frequency (the use
radio-frequency interference, and the like.
oflogarithmicformatsisvalidandpermissible).Therecordingshowsonly
the positive component or envelope of the responses. While this is the 5.7 Care must be taken to ensure that comparable measure-
normal display for a spectrum analyzer, the sinusoidal burst response is
ments are made and that users of the practice follow similar
shown as only one-half of the actual sinusoidal wave.
procedures. The conditions specified or selected (if optional)
may affect the test results and lead to apparent differences.
5. Significance and Use
5.8 Interpretation of some test results, such as the shape of
5.1 This practice is intended to provide standardized proce-
thefrequencyresponsecurve,maybesubjective.Smallirregu-
duresforevaluatingultrasonicsearchunits.Itisnotintendedto
define performance and acceptance criteria, but rather to larities may be significant. Interpretation of the test results is
provide data from which such criteria may be established. beyond the scope of this practice.
5.2 These procedures are intended to evaluate the charac-
5.9 Certain results obtained using the procedures outlined
teristics of single-element piezoelectric search units.
may differ from measurements made with ultrasonic test
instruments.These differences may be attributed to differences
5.3 Implementation may require more detailed procedural
in the nature of the experiment or the electrical characteristics
instructions in a format of the using facility.
of the instrumentation.
5.4 The measurement data obtained may be employed by
users of this practice to specify, describe, or provide a
5.10 The pulse generator used to obtain the frequency
performance criteria for procurement and quality assurance, or
response and time response of the search unit must have a rise
service evaluation of the operating characteristics of ultrasonic
time, duration, and spectral content sufficient to excite the
search units. All or portions of the practice may be used as
search unit over its full bandwidth, otherwise time distortion
determined by the user.
and erroneous results may result.
5.5 Themeasurementsaremadeprimarilyunderpulse-echo
conditions. To determine the relative performance of a search 6. Typical Results Obtainable from Tests Described in
unit as either a transmitter or a receiver may require additional Annex A1 – Annex A5
tests.
6.1 Fig. 1 illustrates some of the typical results that may be
obtained using shock excitation techniques. Values for fre-
quencyresponse,peakfrequency,bandwidth,bandwidthcenter
5 frequency, and time response may be obtained.
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
this test method.
FIG. 1 Test Data Available from Shock Excitation Procedure
E1065/E1065M − 20
FIG. 2 Test Data Available from Sinusoidal Burst Technique
6.2 Fig. 2 illustrates the typical results obtained using the 7. Keywords
sinusoidal burst technique. Values may be obtained for fre-
7.1 aperture; bandwidth; characterization; contact testing;
quencyresponse,peakfrequency,bandwidth,bandwidthcenter
depth of field; focal point; frequency response; immersion
frequency,relativepulse-echosensitivity,andmagnitudeofthe
testing; peak frequency; search unit; sound beam profile; time
electrical impedance from the data recorded with this tech-
response; ultrasound
nique.
ANNEXES
(Mandatory Information)
A1. MEASUREMENT OF FREQUENCY RESPONSE
A1.1 Introduction—The frequency response (also known as generator driving impedance, search unit impedance, pulse
as frequency spectrum) is a measure of the amplitude of the
shape, and measurement systems. The measurement system to
pulse-echo response from a given target as a function of
be used for search unit evaluation should be established by
frequency. This response is used as the basis for establishing
users of the practice.
other operating parameters of the search unit, including peak
A1.2 Shock Excitation Technique—The shock excitation
frequency, center frequency (see Annex A2), bandwidth (see
AnnexA2),andsensitivity(seeAnnexA3).Sketchesoftypical technique for obtaining frequency response is based on the
response curves are shown in Fig. A1.1. These sketches are principlethatashockpulseappliedtothesearchunitproduces
used to describe two conditions: (a) a response that is sym-
a broad spectrum of energies and that the echo from a given
metricalaboutacenterfrequency,and(b)aconditioninwhich
targetreflectsthefrequencydistributionthatischaracteristicof
the frequency response is asymmetrical.
that search unit. Measurements may be made using either the
analog or digitized rf waveform. Fig. A1.2 describes typical
A1.1.1 Two means are described for obtaining the fre-
components used to measure frequency response of an rf
quencyresponse:(a)shockexcitation,and(b)sinusoidalburst.
analog waveform. The system consists of a search unit, shock
The responses obtained using these procedures provide similar
results; however, reproducibility is dependent on factors such pulsegenerator(pulser),preamplifier(receiver),electronicgate
E1065/E1065M − 20
[a] Symmetrical-Response Curve
[b] Asymmetrical-Response Curve
FIG. A1.1 Frequency-Response Curves
that can be adjusted to capture the echo waveform, display digitized rf waveform. The system consists of a search unit,
oscilloscope, and spectrum analyzer. Fig. A1.3 describes typi- pulser, receiver, gate that can be adjusted to capture the echo
cal components used to measure the frequency response of a waveform, analog to digital converter (digitizer), Fourier
E1065/E1065M − 20
FIG. A1.2 Block Diagram of Shock Excitation System Used to Obtain Analog rf Waveform Information
FIG. A1.3 Block Diagram of Shock Excitation System Used to Obtain Digitized rf Waveform Information
transform calculator, and display. To make the measurement, formisinputtotheFouriertransformcalculatoranddisplayed,
an excitation pulse is applied to the search unit and an echo is (seeFig.A1.3).Theresultantspectrumdescribesthefrequency
obtainedfromaspecifictarget.Thegatedechoismonitoredon
response of the search unit.
an oscilloscope to ensure that only the desired rf waveform is
NOTE A1.1—Special Notice for Frequency Response Measurements.
analyzed. The gated analog rf waveform is input to the
With correct settings, the results from the shock excitation and sinusoidal
burst procedures will produce similar results. However, because of the
spectrum analyzer, (see Fig. A1.2). The gated digitized wave-
E1065/E1065M − 20
multiplevariablesassociatedwithelectroniccomponentsandadjustments,
A1.3.1 Fig. A1.4 is a block diagram for a system designed
some differences may result. Users of the practice must identify the
for displaying and recording the frequency response. The
parameters that will be used to make the measurements.
function generator is adjusted to produce sinusoidal bursts
NOTEA1.2—Pulsergeneratorsusedforshockexcitationofsearchunits
across the range of frequencies anticipated for the operating
aresometimesdesignedtohavelowdrivingor onimpedancesandhigh off
impedances. Generally, the duration of the pulse can be adjusted to frequency of the search unit (for example, 1 to 5MHz for
provideamaximumenergytransfertoasearchunit.Asthepulseduration
2.5MHz, 1 to 10MHz for 5MHz, etc.). The generator pulse
and the output impedance of the generator may influence the actual
width is adjusted to provide a minimum pulse duration of 15
spectrumdeliveredtothesearchunit,caremustbeexercisedtoensurethat
cycles at the lowest measurement frequency. The sinusoidal
the spectrum of energies applied is sufficient to accurately describe the
burst (see Fig. A1.4, Position A) is applied to the search unit,
frequency response of the search unit. Operating parameters of the pulser
shouldbeestablishedbyusersofthepractice.Theelectricalimpedanceof
andthepulse-echoresponsefromagiventargetisrecordedfor
the receiver used can have an influence on the frequency response. The
a specific frequency. The frequency of the bursts is stepped
input impedance of the receiver should be known to reduce the potential
through the frequency range, and the pulse-echo voltage
adverse influence.
response is recorded at each frequency. The returning echo is
NOTE A1.3—For measurement of frequency response, a digitizer
capable of providing a minimum of ten samples per cycle at the nominal gated (Position B) to the center one-half of the echo response
frequency of the search unit is recommended. A sufficient number of
to ensure that transients from the generator or electronics do
cycles should be sampled to reliably reproduce the spectrum of the echo
not influence the measurements. Both the amplitude of the
waveform. Averaging a number of waveforms increases the reliability of
applied voltage and the amplitude of the echo response are
measurements. Specific requirements may be established between the
plotted as a function of frequency (Position C).
supplier and user.
NOTEA1.4—When using the shock excitation technique, the returning
A1.3.2 Influence of Generator Output—Commercial sinu-
echo should be gated such that the gate is wider than the echo to ensure
soidal burst generators typically are designed to provide a
that the rising and decaying portions or the waveform are included in the
frequency response analysis. If a portion of the time response is excluded
constant-voltage output into a 50ohm resistance load. When
from the frequency response, this should be clearly documented by
these generators are loaded by an ultrasonic search unit, the
showing the gate position and width relative to the waveform.
output driving voltage may vary with frequency, depending on
the impedance of the search unit.
A1.3 Sinusoidal Burst Technique—Theprincipleistoapply
a sinusoidal burst of a known voltage and frequency to the A1.3.2.1 Recording Procedure—The initial step in the sinu-
search unit and determine its pulse-echo response. By varying soidal burst recording procedure is to terminate the generator
thefrequencyofthesinusoidalburstacrosstheoperatingrange with a 50ohm resistive load and establish that the output
of the search unit and recording the echo response at each voltage is constant over the frequency range of interest. Once
frequency, a plot of the acoustic frequency is obtained (2). this is established, the 50ohm resistor is removed and the
FIG. A1.4 Block Diagram of a Sinusoidal Burst System (Frequency Response)
E1065/E1065M − 20
of a digitizer with the capability of 10 samples per cycle. For the higher
search unit is connected. The frequency response is obtained
frequencies, this recommendation may be modified by the users, but the
without further adjustment of the generator drive voltage. The
digitize capability employed must be documented.
frequency response and the applied voltage are recorded,
The positioning of the gates is essential for accurately analyzing the
thereby showing the influence of the electrical impedance of
frequency response of the search unit. Fig. A1.6 describes examples for
the search unit:
positioning the gate settings for the digitizer. The gate start should be set
at the initiation of the waveform. The gate end should be set at a position
A1.4 Specific Procedures—The sinusoidal burst and shock that encompasses the entire waveform to the 20 dB level. Waveform A
would indicate an approximate 100% bandwidth, while Waveform D
excitation procedures are applicable to nearly all types of
would indicate a bandwidth of approximately 10%.
searchunits.Theproceduresforevaluatingthecharacterization
of various styles are outlined as follows: A1.4.1.2 Focused Search Units—Aball target may be used
to obtain the frequency response of spherically focused search
A1.4.1 Immersion—Fig. A1.5 shows the test setup for
units. The ball should have a diameter that is at least 10
obtaining frequency response for immersion units.
wavelengthsinwater(forexample,15mm[ ⁄8in.]at1MHzin
A1.4.1.1 Flat Search Units—Flatornonfocusedsearchunits
water). Users may specify frequency response be measured on
areadjustedsothatthedistancefromthefaceofthesearchunit
flat plates or rods for cylindrically focused search units. The
to the target (Z ) is a known value (typically 25mm [1in.] or
o
distance Z should be adjusted for maximum amplitude re-
o
50mm [2in.]).Aflat and smooth glass block with dimensions
sponse from the target. Care must be taken to ensure that no
not smaller than 50 by 50mm [2 by 2in.] by 25mm [1in.]
internal reflections from the reflector or creeping wave signals
thick is recommended as the target. A manipulator is used to
around the balls or rods are included in the recorded response,
adjust for a maximum amplitude response from the target.
as these can distort the response.
(a)Thinner blocks may be used for higher frequency
search units. Thicker blocks may be used for lower frequency
A1.4.2 Contact Straight Beam—Measurements for contact
or larger diameter search units, or both, as agreed upon by
straight-beam search units are made with the unit coupled to
users of this practice.
the test block. Couplant shall be machine oil or other specified
(b)Alltargetsortestblocksmusthaveamaterialthickness
fluid. Fig. A1.7 shows the test setup for contact straight-beam
that is greater than the sinusoidal burst pulse duration of the
search units.A38mm [1 ⁄2in.] flat (32µin.) aluminum block,
excitation voltage.
or a block of other suitable material and dimension, may be
used for the frequency response measurements. The back
NOTE A1.5—Guideline for Analyzing Frequency Response. Ultrasonic
surface of the block is used as the target and the echo response
search units used for nondestructive evaluation typically fall with a range
of100kHzto100MHz.Forshockexcitation,NoteA1.3recommendsuse from this surface is recorded.
FIG. A1.5 Test Setup for Immersion Search Units
E1065/E1065M − 20
FIG. A1.6 Digitizer Gate Positioning
FIG. A1.7 Test Setup for Contact Straight-Beam Search Units
NOTE A1.6—Caution: The immersion procedure is not valid for
A1.4.2.1 Thinner blocks may be used for higher frequency
evaluating contact straight-beam search units that incorporate a hard
search units. Thicker blocks may be used for lower frequency
wear-face plate.
or larger diameter search units, or both, as agreed upon by
users of this practice.
A1.4.2.2 All targets or test blocks must have a material
thicknessthatisgreaterthanthesinusoidalburstpulseduration
of the excitation voltage.
E1065/E1065M − 20
A2. BANDWIDTH AND CENTER FREQUENCY MEASUREMENTS
A2.1 The bandwidth (BW) (sometimes referred to as func- f 1f
l u
f 5 (A2.1)
c
tional or operational bandwidth) of a search unit is a selected 2
portion of the frequency response of the search unit.
A2.4 Bandwidth is then calculated as follows:
A2.2 The lower and upper frequency values (f and f
l u
BW 5 f 2 f /f 3100 ~percentage! (A2.2)
~ !
u l c
respectively) of the bandwidth are defined as the values at
whichtheamplitudeofthepulse-echoresponsehasfallen6dB A2.5 By way of example, the bandwidth for the frequency
below the peak of the frequency response curve (f ) (see Fig. responses shown in Fig. A1.1 (a) and (b) are as follows:
p
A1.1). The peak is chosen as the reference even though it may
A2.5.1 Symmetrical Curve (Fig. A1.1 (a)):
not be at the center frequency (f ). Bandwidth measurements
c
f 5 4.016.1 /2 55.05 MHz (A2.3)
~ !
c
are determined by locating the peak response and then select-
BW 5 ~6.1 24.0!/5.05 3100 542% (A2.4)
ing the f and f values.
l u
A2.5.2 Asymmetrical Curve (Fig. A1.1 (b)):
A2.3 Bandwidth calculations are based on determining the
f 5 3.418.2 /2 55.8 MHz (A2.5)
~ !
c
center frequency, f , in MHz, of the bandwidth as described as
c
follows: BW 5 ~8.2 23.4!/5.8 3100 583% (A2.6)
A3. RELATIVE PULSE-ECHO SENSITIVITY
A3.1 Relative pulse-echo sensitivity (S ) is defined as S 520log~0.2/2.0!5220db
rel rel
follows:
Example B:
S 520logV /V expressedindB (A3.1)
~ !
rel e a
f fif V 52.0 V (A3.3)
nom p a
where V is the peak-to-peak voltage response of the echo
e
from the specific reflector as defined in Annex A1, and V is
V 50.1 V
a
e
the peak-to-peak voltage applied to the search unit. Both V
a
S 520log~0.1/2.0!5226db
andV aremeasuredatthenominalfrequency(f ),asstated rel
e nom
NOTE A3.1—Relative pulse-echo sensitivity measurements may be
by the manufacturer’s label.
made with either analog or digitized rf echo waveforms.
NOTE A3.2—No procedure is given in this practice for determining
A3.1.1 Sinusoidal Burst Procedure—Fig.A3.1describesthe
sensitivity using shock excitation procedures.
data for establishing S from the test results obtained with the
rel
sinusoidal burst procedure. The value for S is established at
rel
A3.2 Search unit sensitivity comparisons made with ultra-
f . In the example shown:
nom
sonic instruments may vary from the values obtained with this
Example A:
procedure and they may vary between types of flaw detectors.
f 5 f V 52.0 V (A3.2) Search unit responses are influenced by the impedance of the
nom p a
pulser, impedance of the search unit and coaxial cable, and the
V 5200mV
e input impedance of the receiver.
E1065/E1065M − 20
FIG. A3.1 Measurement of Sensitivity from Sinusoidal Burst Frequency Response Curve
A4. MEASUREMENT OF TIME RESPONSE
A4.1 Time Response—Thetimeresponseofasearchunitis can be defined. Example is shown in Fig. 1. The terms and
established from the rf waveform of the echo received from a parameters selected in the quantitative description of wave-
given target using the pulse-echo procedure. This response is forms (for example, waveform duration, resolution, and damp-
used as the basis for evaluating other operating and recovery ing) should be defined and agreed upon by users of this
parameters of the search unit such as waveform duration and practice.Waveformdurationmaybemeasuredasaleveleither
damping (Standard Methods forTesting Single Element Pulse- 20 or 40 dB below the peak of the pulse-echo response.As the
Echo Ultrasonic Transducers). Typical examples of waveform time response can be influenced by the input electronics and
duration are shown in Fig. A4.1. impedanceofthereceiver,caremustbetakentoensurethatthe
receiver input is not saturated and that the impedance is high
A4.2 Procedure—The procedure for measuring the time
enough(forexample,500ohmsorgreater)toaccuratelyrecord
response employs the shock excitation techniques defined in
the echo signal.
A1.2 and the procedures outlined in A1.4. Fig. A1.2 and Fig.
NOTEA4.1—This practice does not describe a procedure for obtaining
A1.3 illustrate the setup for pulse-echo procedure. Fig. A1.5 “time response” using the sinusoidal burst excitation procedure.
NOTE A4.2—For accurate measurement of the time response of a
and Fig. A1.7 illustrate the test configuration for immersion
digitized rf waveform, an 8-bit digitizer is needed.Asufficient number of
and contact straight-beam search units.
samplespercycleshouldbetakenthatacurvethroughthesampledvalues
provides a smooth waveform that resembles the original analog wave-
A4.3 Time Response Terms and Parameters—A photo-
form. For reliable measurement of peak or low-level waveforms, a
graphorprintoutoftherfwaveformfromtheCRTcanbeused
minimum sampling of 36 samples per cycle is recommended. An 8-bit
to described the time response of the search unit. This record
digitizer is inherently limited to displaying 48 dB of dynamic range and
onlyhalfofthisrangeisusableforevaluatinganrfwaveform,toevaluate
shouldprovideascaledtimebasefromwhichthemeasurement
low level signals may require increasing the gain of the amplifier.
Averaging a number of waveforms increases the reliability. Specific
See AIUM Standard Methods (2.2).
requirements may be established between the supplier and user.
E1065/E1065M − 20
FIG. A4.1 Time Responses (Waveform Duration)
A5. ELECTRICAL IMPEDANCE MEASUREMENTS
A5.1 The magnitude and phase of the electrical impedance ment of the applied current as a function of frequency. The
of a search unit may be determined using an impedance meter. value for the magnitude of the electrical impedance is deter-
The magnitude of the electrical impedance of the search unit mined at the nominal frequency of the search unit (f ).
nom
may be determined using the sinusoidal burst technique and
Z?5 V /I (A5.1)
?
a a
measuring the voltage and current applied to the search unit.
where V is the applied voltage and I is the applied current
a a
A5.1.1 Electrical Impedance to be Measured with an Im-
at f . Fig.A5.1 shows a sketch of the responses from which
nom
pedance Meter—Refer to the instruction manual for the im-
the impedance measurements are measured. For using the
pedance meter being used for procedures to obtain the magni-
sinusoidalbursttechnique,measurementsshallbemadewitha
tude and phase angle of the complex impedance of the unit
coaxial cable attached to the search unit. For purposes of this
being measured.
practice, a 1.2 m [4 ft] long cable is recommended.
A5.1.2 Electrical Impedance to be Measured with Sinusoi-
dal Burst Technique—Fig. A1.4 describes the block diagram NOTE A5.1—All impedance measurements are to be made under
conditionsthatapplyappropriateloadingtothefaceofthesearchunit.As
used for measuring the frequency response of a search unit.
examples, immersion units should be measured in water; contact units
The same electrical setup may be used for measuring the
should be coupled to a metal block. No coupling load (impedance
magnitude of the electrical impedance of the search unit. The
measurements in air) may be advisable when uniform hard face coupling
voltageprobeprovidesameasurementoftheappliedvoltageas
is difficult to achieve. Precautions should be made to ensure that no
afunctionoffrequency.Thecurrentprobeprovidesameasure- standing wave interference occurs in the water tank or test block.
FIG. A5.1 Typical Voltage and Current Recordings for Determining Magnitude of Search Unit Impedance
E1065/E1065M − 20
A6. MEASUREMENT OF SOUND FIELD PARAMETERS
A6.1 Introduction—This section describes procedures for broad so that no adverse response is introduced by the
measuring sound field parameters of immersion flat and
hydrophone. A hydrophone may be a miniature search unit
focused search units. Either analog or digital equipment may
withasmallpiezoelectricelementormaybeconstructedusing
be used.
appropriate commercial immersion search units by attaching a
sound-absorbing mask (for example, cork) which has a small
A6.2 Test Setup—This procedure outlines a means for
centerpinholetothefaceofthesearchunit.Fig.A6.3describes
employing a pulse-echo technique using a ball target reflector.
the hydrophone with the sound-absorbing mask.
A second procedure using a hydrophone receiver is also
described. For purposes of this practice, the transmission
A6.3 Immersion Flat (Nonfocused) Search Units—Four
patternandthereceptionpatternsofsearchunitsareconsidered
parameters are identified as important for evaluating the
identical and reciprocal.The search unit may be excited with a
characteristicsofimmersionflatsearchunits:(a)aperturesize,
shock excitation pulse or with a sinusoidal burst at center
(b) traverse profile, (c) on-axis profile, and (d) sound beam
frequency, f .
c
spread.
A6.2.1 The test setup for pulse-echo measurements is
A6.3.1 Ball Target Measurements:
shown in Fig. A6.1. The test setup for hydrophone measure-
A6.3.1.1 The sketch in Fig. A6.1 shows a setup for obtain-
ments is shown in Fig. A6.2. The setup includes a pulse
ingsound-fieldparametersusingthepulse-echoreflectionfrom
generator, preamplifier, echo gate that can be adjusted to
capture the echo, search unit, target or hydrophone, a peak a ball target reflector.As the sound beam transmitted from the
detector, and a XY recorder. The peak detector output is the searchunitisassumedtobeidenticaltothesoundbeampattern
Y-axis input. The X-axis input is the analog output from the
ofthesearchunitinareceivingmode,thepulse-echoresponse
X-Y-Z manipulator of the bridge carriage and immersion tank
is the product of the two sound beams. Accordingly, various
scanning and indexing equipment.
parameters such as aperture size and sound beam spread are
measured to different levels on the response curve depending
A6.2.2 Ball Target—The ball target chosen for the pulse-
onthetechniqueemployed.Asanexample,whenusingtheball
echo procedure should be a small smooth sphere (for example,
target,pulse-echotechnique,measurementsaremadetoalevel
a diameter equal to 10 wavelengths (λ) in water).
that is-6 dB below the peak of the response. With use of the
A6.2.3 Hydrophone—Two types of hydrophones may be
hydrophone technique, the measurements are made to a level
employed. The most desirable is the hydrophone that has an
that is-3 dB below peak of the response. Commercial systems
active element with a diameter less than 2λ of the center
are available for making such measurements.
frequency, f , of the search unit as measured in water. If the
c
A6.3.1.2 An example of the procedure for obtaining sound
element is larger than this dimension, a correction factor must
be added to include the directivity function of the hydrophone. beam parameters using ball target measurements is as follows
Frequency response of the hydrophone must be sufficiently (see Fig. A6.1):
FIG. A6.1 Test Setup for Measuring Sound Field Patterns with Pulse-Echo Technique Using Ball Target Reflector
E1065/E1065M − 20
FIG. A6.2 Test Setup for Measuring Sound Field Patterns Using Hydrophone Procedure
FIG. A6.3 Cork Mask for Adapting Commercial Search Units to Small Hydrophone
(a)Place a flat target that is perpendicular to the bridge near-far-fieldtransition, Z ,orotherpointssuchas Z /2, Z /3,
n n n
carriage in the tank and adjust the θ and φ axis of the or 2Z , may be appropriate if a sinusoidal burst excitation is
n
manipulator holding the search unit to obtain maximum
employed. For shock excitation, it may be more appropriate to
pulse-echo response from the target.
use specific distances (for example, 25, 75, 125, etc. mm [1, 3,
(b)Place the ball target in the tank at a fixed location and
5, etc. in.]). For reference purposes, the near-far-field transi-
position the search unit so that it is located at a distance that is
tions for various aperture sizes may be calculated from the
inthefarfield(beyondpeakresponseforfocusedunits).Adjust
following:
the X-Y- Z manipulator to obtain maximum response from the
CircularPiston, Z 5 d /4λ (A6.1)
n
ball target. (Alternatively, the search unit may be fixed and the
ball target moved.)
where:
A6.3.1.3 Aperture Size—To obtain aperture size (see Fig.
Z = distance from search unit face to far field transition,
n
A6.4 (c) Position 1), move the search unit close to the ball
λ = wavelength, and
target (for example, 1.5 mm [ ⁄16 in.]) and scan the target. Care
d = aperture.
must be exercised to ensure that the echo in the gate contains
Squareelement ~A 3ADimension! (A6.2)
only the energy from the ball target. The aperture size is
definedasthedimensionofthepressurepatternasmeasuredto 2
Z 51.35 A /4λ
n
the-6 dB level below the average response across the center
(See Ref (3).)
portion of the search unit.
To establish beam patterns or beam symmetry, the beam
A6.3.1.4 Transverse Profiles—Transverse profiles are ob-
should be plotted in two orthogonal directions at the near-far
tained by scanning the ball target through the sound beam at
fieldtransitionorotherselecteddistances,orboth,asagreedby
selected distances away from the face of the search unit (see
Fig. A6.4). Selection of theoretical positions such as the the users.
E1065/E1065M − 20
[a] Transverse Profile
[b] On-Axis Profile Distribution [Shock Excitation]
[c] Transverse Profile Distribution
[d] Sound Beam Spread
FIG. A6.4 Sound Field Patterns for Establishing Search Unit Performance Parameters
A6.3.1.5 On-Axis Profiles—On-axisprofileisobtainedfrom target measurements, the responses are measured to a level
the transverse profile by recording the amplitude of the center -6dB below peak response. The beam spread (2ψ) is then
of the transverse plots as a function of distance, Z, from the calculated as follows:
face of the search unit (see Fig. A6.4). Alternatively, if the
2ψ 52 Arctan W/ Z 2 Z (A6.3)
~ !
c a
center of the beam can be established, the ball target may be
moved along the axis of the beam and record the on-axis (See Fig. A6.4.)
pressure response as a function of distance. This procedure is
where:
more difficult as it is hard to maintain the central axis of the
Z = distance beyond the near-far field transition,
a
beam as the ball target is moved away from the face of the
Z = selected distance beyond Z , and
c a
search unit.
W = measured increase in sound field width.
A6.3.1.6 Beam Spread—Beam spread is a measure of the
beam divergence as a function of distance beyond the near-far A6.3.2 Hydrophone Measurements—Fig. A6.4 shows
field transition (see Fig. A6.4). Beam spread may be deter- sketches of typical results for flat immersion search units. A
mined from the transverse plots or by measuring the sound procedure for obtaining these parameters with hydrophone
field pattern at two or more locations in the far field. The measurements is as follows (see Fig. A6.2):
procedure is to establish the width of the sound beam at a (a)Place a flat target that is perpendicular to the bridge
specificdBvaluebelowpeakresponseatthatposition.Forball carriage in the tank and adjust the φ and θ axis of the
E1065/E1065M − 20
manipulator holding the search unit to obtain maximum (F ), and depth of field (F ). Once the maximum amplitude
P D
pulse-echoresponsefromthetarget.Thisensuresthatscanning response is obtained from the target, the search unit is moved
and indexing will be normal and parallel to the axis of the
toward the target until the amplitude drops 6 dB (50%) below
sound field.
the peak. This distance is noted as the lower position of the
(b)Placethehydrophoneonthescanningbridgeandcenter
depth of field. The search unit is then moved through the peak
the hydrophone by placing it in the far field and adjust the
andbeyonduntiltheamplitudedrops6dBbelowthepeak.The
hydrophone to obtain maximum or peak response
distance between these two positions (F through F ) defines
1 2
(alternatively,thehydrophonemaybefixedandthesearchunit
the depth of field (F ) of focused search units. When making
D
moved).
these measurements, care must be taken to ensure that the
A6.3.2.1 Aperture Size—To obtain aperture size, move the
targetremainsdirectlyontheaxisofthesearchunit.Misalign-
hydrophone close to the face of the search unit (for example,
ment can result in erroneous measurements.
1.5 mm [ ⁄16 in.]) and scan the beam. The aperture size of the
A6.4.1.1 Thedepthoffieldisdefinedasthedistance F –F .
2 1
sound beam is defined as the dimension of the pressure pattern
The values for F and F may be obtained using a pulse-echo
1 2
as measured to the−3 dB level below the average response
response from a ball target reflector or in a transmission mode
across the center portion of the search unit minus the radius of
using the hydrophone technique. However, if the hydrophone
the hydrophone. See Fig. A6.4(c), Position 1.
technique is used, the depth of field, F , is measured to
A6.3.2.2 Transverse Profiles—Transverse profiles are ob-
D
tained by recording the response from the hydrophone as the−3dB below the amplitude at peak response instead of
measuredatselecteddistancesawayfromthefaceofthesearch
−6dB below the amplitude at peak response as used in
unit. The same conditions apply to hydrophone measurements
pulse-echo procedures.
as applied for the ball target measurements (see A6.3.1.4).
A6.4.2 Diameter at Focal Point—The diameter at the focal
A6.3.2.3 On-Axis Profiles—On-axis profiles are obtained in
point, d , of a search unit may be obtained using either the
FP
a manner similar to that followed for ball target measurements
pulse-echo response from a ball target or by using the hydro-
(see A6.3.1.5). As with other hydrophone measurements, care
phone technique. The initial step in this procedure is to locate
mustbetakentoensurethattheresponsefromthehydrophone
the focal peak. After the peak is located, a cross-axial plot
falls within the gate.
provides the diameter at the focal point. When using the
A6.3.2.4 Beam Spread—Beam spread is measured in the
samemannerasdescribedfortheballtargetmeasurements(see pulse-echo,balltargettechnique,thediameteratthefocalpoint
A6.3.1.6).Thebasicdifferenceisthatbeamspreadismeasured is defined as the width of the sound beam measured to
at a level of−3 dB below the peak response obtained at the
the−6dB level. When the hydrophone technique is used, the
position measured instead of the 6 dB level as followed for the
diameter at the focal p
...