ISO 16063-41:2011

INTERNATIONAL ISO
STANDARD 16063-41
First edition
2011-08-01
Methods for the calibration of vibration
and shock transducers —
Part 41:
Calibration of laser vibrometers
Méthodes pour l'étalonnage des transducteurs de vibrations et de
chocs —
Partie 41: Étalonnage des vibromètres à laser

Reference number
©
ISO 2011
©  ISO 2011
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ii © ISO 2011 – All rights reserved

Contents Page
Foreword . iv
1  Scope . 1
2  Normative references . 1
3  Classification of laser vibrometers and principles of test methods . 2
4  Uncertainty of measurement . 4
5  Requirements for apparatus and other conditions . 5
6  Preferred amplitudes and frequencies . 14
7  Common procedure for primary calibration (methods 1, 2 and 3) . 15
8  Method using fringe counting (method 1) . 15
9  Method using minimum-point detection (method 2) . 16
10  Methods using sine approximation: method 3 (homodyne version) and method 3
(heterodyne version) . 18
11  Method using comparison to a reference transducer (method 4) . 20
12  Report of calibration results . 21
Annex A (normative) Uncertainty components in the primary calibration by laser interferometry of
vibration and shock transducers . 31
Annex B (informative) Three versions of method 3 based on laser Doppler velocimetry . 36
Annex C (informative) Example of calculation of measurement uncertainty in calibration of a laser
vibrometer . 40
Annex D (informative) Phase shift calibration of laser vibrometers . 42
Bibliography . 44

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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 16063-41 was prepared by Technical Committee ISO/TC 108, Mechanical vibration, shock and condition
monitoring, Subcommittee SC 3, Use and calibration of vibration and shock measuring instruments.
ISO 16063 consists of the following parts, under the general title Methods for the calibration of vibration and
shock transducers:
 Part 1: Basic concepts
 Part 11: Primary vibration calibration by laser interferometry
 Part 12: Primary vibration calibration by the reciprocity method
 Part 13: Primary shock calibration using laser interferometry
 Part 15: Primary angular vibration calibration by laser interferometry
 Part 21: Vibration calibration by comparison to a reference transducer
 Part 22: Shock calibration by comparison to a reference transducer
 Part 31: Testing of transverse vibration sensitivity
 Part 41: Calibration of laser vibrometers
The following parts are under preparation:
 Part 16: Calibration by Earth's gravitation

iv © ISO 2011 – All rights reserved

INTERNATIONAL STANDARD ISO 16063-41:2011(E)

Methods for the calibration of vibration and shock
transducers —
Part 41:
Calibration of laser vibrometers
1 Scope
This part of ISO 16063 specifies the instrumentation and procedures for performing primary and secondary
calibrations of rectilinear laser vibrometers in the frequency range typically between 0,4 Hz and 50 kHz. It
specifies the calibration of laser vibrometer standards designated for the calibration of either laser vibrometers
or mechanical vibration transducers in accredited or non-accredited calibration laboratories, as well as the
calibration of laser vibrometers by a laser vibrometer standard or by comparison to a reference transducer
calibrated by laser interferometry. The specification of the instrumentation contains requirements on laser
vibrometer standards.
Rectilinear laser vibrometers can be calibrated in accordance with this part of ISO 16063 if they are designed
as laser optical transducers with, or without, an indicating instrument to sense the motion quantities of
displacement or velocity, and to transform them into proportional (i.e. time-dependent) electrical output signals.
These output signals are typically digital for laser vibrometer standards and usually analogue for laser
vibrometers. The output signal or the reading of a laser vibrometer can be the amplitude and, in addition,
occasionally the phase shift of the motion quantity (acceleration included). In this part of ISO 16063, the
calibration of the modulus of complex sensitivity is explicitly specified (phase calibration is provided in
Annex D).
NOTE Laser vibrometers are available for measuring vibrations having frequencies in the megahertz and gigahertz
ranges. To date, vibration exciters are not available for generating such high frequencies. The calibration of these laser
vibrometers can be estimated by the electrical calibration of their signal processing subsystems utilizing appropriate
synthetic Doppler signals under the following preconditions:
 the optical subsystem of the laser vibrometer to be calibrated has been proven to comply with defined requirements
comparable to those given in 5.5.3;
 synthetic Doppler signals are generated as an equivalent substitute for the output of the photodetectors.
More detailed specifications of this approach (see Reference [25]) lie outside the scope of this part of ISO 16063.
2 Normative references
The following referenced documents are indispensable for the application 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 266, Acoustics — Preferred frequencies
ISO 5348, Mechanical vibration and shock — Mechanical mounting of accelerometers
ISO 16063-1:1998, Methods for the calibration of vibration and shock transducers — Part 1: Basic concepts
ISO 16063-11:1999, Methods for the calibration of vibration and shock transducers — Part 11: Primary
vibration calibration by laser interferometry
ISO 16063-21, Methods for the calibration of vibration and shock transducers — Part 21: Vibration calibration
by comparison to a reference transducer
ISO/IEC Guide 99, International vocabulary of metrology — Basic and general concepts and associated terms
(VIM)
3 Classification of laser vibrometers and principles of test methods
3.1 Classification of laser vibrometers
3.1.1 A laser vibrometer standard (LVS) is a reference standard containing a laser interferometer,
designed and intended to serve as a reference to calibrate laser vibrometers and/or vibration transducers.
NOTE Methods 1, 2, and 3 are applicable to the primary calibration of LVSs.
3.1.2 A laser vibrometer (LV) is a measuring instrument containing a laser interferometer, designed and
intended to perform vibration measurements.
NOTE Methods 1, 2, and 3 are applicable to the primary calibration of LVs, and method 4 is applicable to the
secondary calibration of LVs. The reference accelerometer used for method 4 is calibrated by method 1, 2 or 3. For
specific requirements, see 5.11.
3.1.3 A laser optical transducer is a measurement transducer sensing, by laser light, the motion quantities
of displacement or velocity and transforming these quantities into a proportional time-dependent output signal.
3.2 Principles of test methods
3.2.1 General. Four methods are specified in analogy to ISO 16063-11 (laser interferometry) and
ISO 16063-21 (comparison to a reference transducer), respectively. Methods 1, 3, and 4 provide for
calibrations at preferred displacement amplitudes, velocity amplitudes and acceleration amplitudes at various
frequencies. Method 2 requires calibrations at fixed displacement amplitudes (velocity amplitude and
acceleration amplitude vary with frequency).
For each interferometric method specified in this part of ISO 16063 (see 3.2.2 to 3.2.4), currently a specific
frequency range applies. In fact, the applicability of the particular methods mainly depends on the
displacement or velocity amplitudes measurable within given measurement uncertainties. These, however, not
only depend on the measurement method itself but also on the frequency-dependent properties of the
vibration exciters available. Using adequate vibration exciters to generate sufficient displacement or velocity
amplitudes, the upper frequency limits of all methods can be expanded to 100 kHz and even beyond. The
primary method 3 (see 3.2.4) and the comparison method 4 (see 3.2.5) are applicable at frequencies lower
than 0,4 Hz.
3.2.2 Method 1, the fringe-counting method, is a vibration measurement method using a homodyne
interferometer with a single output (see Note 2) in conjunction with instrumentation for fringe counting of the
interferometer signal. Considering that the displacement corresponding to the distance between two fringes
(intensity maxima or intensity minima) is given by half the wavelength of the principal lines in the emission
spectrum of neon of the He-Ne laser, the displacement amplitude can be calculated from the number of
fringes counted during a given number (e.g. 1 000) of vibration periods.
For details, see Clause 8 and, for further information, ISO 16063-11:1999, B.1.
NOTE 1 Method 1 is applicable to the primary calibration of the laser vibrometer (modulus only) in the frequency range
1 Hz to 800 Hz and, under special conditions, at lower and higher frequencies. In Reference [26], the applicability of
method 1 has been demonstrated at frequencies up to 347 kHz.
NOTE 2 Alternatively, the homodyne interferometer signal from one of the two outputs of a quadrature interferometer
can be used.
2 © ISO 2011 – All rights reserved

NOTE 3 The electronic fringe counting can be substituted by the signal coincidence method (see References [1] [23]
[24]), which indicates a displacement amplitude of a quarter wavelength, /4, of the laser light (158,2 nm for a red helium-
neon laser). In the general case, the interferometer signal shows relative maxima and minima at the times when the
vibration displacement approaches its positive and negative peak values, respectively. In the discrete case (158,2 nm), the
relative signal maxima and minima approach the same signal level from the negative and positive directions, respectively
(“coincidence”). By observing the interferometer signal as a function of time on an oscilloscope and adjusting the vibration
amplitude to the level where a bright sharp line appears, the discrete amplitude (158,2 nm) is identified. The bright line
varies with time as the initial phase of the interferometer signal varies due to low-frequency motion. In Reference [26], the
applicability of the signal coincidence method has been demonstrated at frequencies up to 160 kHz.
3.2.3 Method 2, the minimum-point method, is a vibration measurement method using a homodyne
interferometer with a single output in conjunction with instrumentation for zero-point detection of a component
of the frequency spectrum of the interferometer signal. Considering the frequency spectrum of the intensity
and adjusting the vibration amplitude to the level at which the component of the same frequency as the
vibration frequency is zero, the displacement amplitude can be calculated from the argument corresponding to
the respective zero point of the
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