ASTM E1781-98

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: E 1781 – 98
Standard Practice for
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Secondary Calibration of Acoustic Emission Sensors
This standard is issued under the fixed designation E 1781; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.2.1 reference sensor (RS)—a sensor that has had its
response established by primary calibration (also called sec-
1.1 This practice covers requirements for the secondary
ondary standard transducer) (see Method E 1106).
calibration of acoustic emission (AE) sensors. The secondary
3.2.2 secondary calibration—a procedure for measuring the
calibration yields the frequency response of a sensor to waves
frequency or transient response of an AE sensor by comparison
of the type normally encountered in acoustic emission work.
with an RS.
The source producing the signal used for the calibration is
3.2.3 test block—a block of homogeneous, isotropic, elastic
mounted on the same surface of the test block as the sensor
material on which a source, an RS, and a SUT are placed for
under testing (SUT). Rayleigh waves are dominant under these
conducting secondary calibration.
conditions; the calibration results represent primarily the sen-
sor’s sensitivity to Rayleigh waves. The sensitivity of the
4. Significance and Use
sensor is determined for excitation within the range of 100 kHz
4.1 The purpose of this practice is to enable the transfer of
to 1 MHz. Sensitivity values are usually determined at frequen-
calibration from sensors that have been calibrated by primary
cies approximately 10 kHz apart. The units of the calibration
calibration to other sensors.
are volts per unit of mechanical input (displacement, velocity,
or acceleration).
5. General Requirements
1.2 The values stated in SI units are to be regarded as the
5.1 Units for Calibration—Secondary calibration produces
standard. The values given in parentheses are for information
the same type of information regarding a sensor as does
only.
primary calibration (Method E 1106). An AE sensor responds
1.3 This standard does not purport to address all of the
to motion at its front face. The actual stress and strain at the
safety concerns, if any, associated with its use. It is the
front face of a mounted sensor depends on the interaction
responsibility of the user of this standard to establish appro-
between the mechanical impedance of the sensor (load) and
priate safety and health practices and determine the applica-
that of the mounting block (driver); neither the stress nor the
bility of regulatory limitations prior to use.
strain is amenable to direct measurement at this location.
2. Referenced Documents However, the free displacement that would occur at the surface
of the block in the absence of the sensor can be inferred from
2.1 ASTM Standards:
measurements made elsewhere on the surface. Since AE
E 114 Practice for Ultrasonic Pulse-Echo Straight-Beam
2 sensors are used to monitor motion at a free surface of a
Examination by the Contact Method
structure and interactive effects between the sensor and the
E 494 Practice for Measuring Ultrasonic Velocity in Mate-
2 structure are generally of no interest, the free motion is the
rials
appropriate input variable. It is therefore required that the units
E 1106 Method for Primary Calibration of Acoustic Emis-
2 of calibration shall be volts per unit of free displacement or free
sion Sensors
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velocity, that is, volts per metre or volt seconds per metre.
E 1316 Terminology for Nondestructive Examinations
5.2 The calibration results may be expressed, in the fre-
3. Terminology quency domain, as the steady-state magnitude and phase
response of the sensor to steady-state sinusoidal excitation or,
3.1 Definitions—Refer to Terminology E 1316, Section B,
in the time domain, as the transient response of the sensor to a
for terms used in this practice.
delta function of displacement.
3.2 Definitions of Terms Specific to This Standard:
5.3 Importance of the Test Block Material—The specific
acoustical impedance (rc) of the test block is an important
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This practice is under the jurisdiction of ASTM Committee E-7 on Nonde- parameter that affects calibration results. Calibrations per-
structive Testing and is the direct responsibility of Subcommittee E07.04 on
formed on blocks of different materials yield sensor sensitivi-
Acoustic Emission Method.
ties that are very different. For example, a sensor that has been
Current edition approved Dec. 10, 1998. Published February 1999. Originally
calibrated on a steel block, if calibrated on a glass or aluminum
published as E 1781–96. Last previous edition E 1781–96.
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