Measurement
Science and Technology
Highlights of 2014

Editor-in-Chief: D J S Birch, Strathclyde University, UK
ww
ISSN 0957-0233

Measurement
Science and Technology

Volume 25 Number 9 September 2014
Special feature
ASPEN 2013 (Taipei)
Guest editors: Kuang-Chao Fan and Wei Gao

Dear Colleagues
I am delighted to present the Measurement Science and Technology (MST) Highlightsof 2014, a selection of the very best research published by the journal in 2014. These
highlights show the tremendous diversity of areas covered by the journal. Articles in
MST represent the highest quality research in measurement science, and are publishedfollowing a rigorous peer-review process, which accepts fewer than one in threesubmissions to the journal.
The articles presented here have been selected by the journal’s Editorial Board, with theguidance of our team of expert referees, as some of the highest quality papers we havepublished in 2014. I hope that you find them interesting.

iopscience.org/mst

IMPACT FACTOR

1.433

*

*As listed in the 2014 ISI Journal
Citation Reports®

To read the full-text articles, or to submit your own work to Measurement Science andTechnology, please go to iopscience.org/mst. All these articles have been made free toread to the end of 2015.
Ian Forbes
Publisher, Measurement Science and Technology

Winner of 2014 Outstanding Paper Award
Fluid mechanics

A combined scanning PTV/LIF technique
to simultaneously measure the full velocity
gradient tensor and the 3D density field
D Krug, M Holzner, B Lüthi, M Wolf, A Tsinober and W Kinzelbach
Abstract
We present a newly developed combined scanning particle tracking velocimetry(SPTV) and scanning laser-induced fluorescence (SLIF) technique. The new
method allows for the first time to measure the full velocity gradient tensor
and the three-dimensional density field simultaneously in a refractive index
matched environment. The data thus obtained will be valuable in investigating
the interaction between turbulence, i.e. the dynamics of vorticity and strain,
and the density field. In this study, we describe the implementation of themeasurement system in detail. As a showcase, the new technique is applied toa gravity current flow and the measured data are validated by imposing various
checks. Further results are presented that illustrate the capability of the SPTV/SLIF technique in the investigation of interface dynamics

Figure taken from D Krug et al 2014 Meas. Sci. Technol. 25 065301

Did you know?
MST is the oldest measurement journal in theworld, originally published as Journal of Scientific
Instruments in 1923

2014 Meas. Sci. Technol. 25 065301
iopscience.org/mst 		Measurement Science and Technology: Highlights 20141

Winner of 2014 Outstanding Paper Award
Optical and laser-based techniques

deviations of a sphere can be characterized reliably, which benefits the effortsof reducing the form deviations of the silicon spheres of the Avogadro project.
In other fields where spheres are used as references, accurate knowledge of thereal form may be helpful for further improvements.

Bootstrapping de-shadowing and selfcalibration for scanning electron microscope
photometric stereo

2014 Meas. Sci. Technol. 25 064002

Atsushi Miyamoto, Deshan Chen and Shun'ichi Kaneko
Abstract
In this paper, we present a novel approach that addresses the blindreconstruction problem in scanning electron microscope (SEM) photometricstereo. Using only two observed images that suffer from shadowing effects,
our method automatically calibrates the parameter and resolves shadowing
errors for estimating an accurate three-dimensional (3D) shape and underlying
shadowless images. We introduce a novel shadowing compensation modelusing image intensities for both cases of presence and absence of shadowing.
With this model, the proposed de-shadowing algorithm iteratively compensates
for image intensities and modifies the corresponding 3D surface. Besides
de-shadowing, we introduce a practically useful self-calibration criterion
by enforcing a good reconstruction. We show that incorrect parameters will
engender significant distortions of 3D reconstructions in shadowed regions
during the de-shadowing procedure. This motivated us to design the selfcalibration criterion by utilizing shadowing to pursue the proper parameterthat produces the best reconstruction with least distortions. As a result, wedevelop a bootstrapping approach for simultaneous de-shadowing and selfcalibration in SEM photometric stereo. Extensive experiments on real image
data demonstrate the effectiveness of our method.
2014 Meas. Sci. Technol. 25 105402
Figure taken from Atsushi Miyamoto
et al 2014 Meas. Sci. Technol. 25
105402

Improving the accuracy of the transientplane source method by correcting probeheat capacity and resistance influences
Yanning Li, Chunfeng Shi, Jian Liu, Errui Liu, Jian Shao, Zhi Chen,
Dante J Dorantes-Gonzalez and Xiaotang Hu
Abstract
The transient plane source (TPS) method is a relatively newly developed
transient approach for thermal conductivity measurement. Compared with thesteady-state method, it is fast, and applicable to either solid, liquid or gas statematerials; therefore, it has gained much popularity in recent years. However,during measurement, the measured power is influenced by the heat capacityof the electrical isolation films as well as the electrical resistance change of themetallic thin wire of the TPS probes. This further influences the measurement
precision. Meanwhile, these two factors have been ignored in the traditionalmodel of TPS developed by Gustafsson. In this paper, the influence of both theheat capacity and the resistance change of the TPS probe on the measured
power is studied, and mathematical formulas relating the two factors and theirrespective corrections are deduced. Thereafter an improved model is suggested
based on the traditional TPS model and the above theoretical models.
Experiments on polymethylmethacrylate (PMMA) standard materials have been
conducted using a home-made system, including TPS probes, data acquisition
module and analysis software. The results show that the improved model caneffectively improve the measurement precision of the TPS method by about
1.8–2.3% as evaluated by relative standard deviation.
2014 Meas. Sci. Technol. 25 015006

Microwave based method of monitoringcrack formation
Sergej Aman, Alexander Aman, Soeren Majcherek, Soeren Hirsch andBertram Schmidt

PTB's enhanced stitching approach for thehigh-accuracy interferometric form error
characterization of spheres
Guido Bartl, Michael Krystek and Arnold Nicolaus
Abstract
The stitching procedure that was presented a few years ago allowed thereconstruction of the real shape of a sphere from the measured datathat had been acquired by the sphere interferometer of the PhysikalischTechnische Bundesanstalt. The enhancements described in this paper involve
additional information from the measurements that could not be taken into
account before. Therefore, not only the determination of the uncertaintyof the reconstructed results is enabled, but also the occurrence of largescale systematic deviations can be prevented. As a consequence, the form

2 Measurement Science and Technology: Highlights 2014

Abstract
The formation of cracks in glass particles was monitored by application of
linearly polarized microwaves. The breakage behavior of glass spheres coatedwith a thin gold layer of about 50 nm, i.e. a thickness that is lower than the
microwave penetration depth, was tested. In this way the investigation of
fracture behavior of electronic circuits was simulated. A shielding current was
induced in the gold layer by the application of microwaves. During the crack
formation the distribution of this current changed abruptly and a scatteredmicrowave signal appeared at the frequency of the incident microwaves.
The time behavior of the scattered signal reflects the microscopic processes
occurring during the fracture of the specimen. The duration of the increasing
signal corresponds to the crack formation time in the tested specimen. This
time was estimated as particle size divided by crack development speed inglass. An intense emission of electrons occurs during the formation of cracks.
Due to this, coherent Thomson scattering of microwaves by emitted electrons
becomes significant with a delay of a few microseconds after the initial phaseof crack formation. In this time the intensity of the microwave signal increases.
2014 Meas. Sci. Technol. 25 025014
iopscience.org/mst

Winner of 2014 Outstanding Paper Award
Biological, medical and life sciences

A multifrequency eletromagnetic applicatorwith an integrated AC magnetometer formagnetic hyperthermia experiments
E Garaio, J M Collantes, F Plazaola, J A Garcia and I Castellanos-Rubio
Abstract
In the present paper, a lab-made electromagnetic applicator for magnetic
hyperthermia experiments is described, fabricated and tested. The proposed
device is able to measure the specific absorption rate (SAR) of nanoparticle
samples at different magnetic field intensities and frequencies. Based ona variable parallel LCC resonant circuit fed by a linear power amplifier, theelectromagnetic applicator is optimized to generate a controllable andhomogeneous AC magnetic field in a 3.5 cm3 cylindrical volume, in a wide
frequency range of 149–1030 kHz with high field intensities (up to 35 kA m−1
at low frequencies and up to 22 kA m−1 at high frequencies). In addition, a labmade AC magnetometer is integrated in the electromagnetic applicator. The AC
magnetometer is fully compensated to provide accurate measurements of the
dynamic hysteresis cycle for nanoparticle powders or dispersions. From these
dynamic hysteresis loops the SAR of the nanoparticle samples can be directly
obtained. To show the capabilities of the proposed set-up, the AC hysteresis
loops of two different magnetite nanoparticle samples with different sizes havebeen measured for various field intensities and frequencies. To our knowledge,
no other work reports an electromagnetic applicator system with integrated AC
magnetometer providing such characteristics in terms of frequency and intensity.
2014 Meas. Sci. Technol. 25 115702

Application of order cyclostationary
demodulation to damage detection in a
direct-driven wind turbine bearing
Xiaofeng Liu, Lin Bo and Chang Peng
Abstract
This paper presents a method of fault detection and isolation for a direct-driven
wind turbine (DWT) bearing. Computed order tracking is employed to convert
the non-stationary envelope signal in the time domain into a quasi-stationary
signal in the angular domain by even-angle resampling. Cyclostationary
demodulation is then utilized to expose the orders related to fault
characteristics in the demodulation spectrum. In order to realize the automatic
fault diagnosis and emit a stable alarm about bearing damage, the peak valueof the demodulation spectrum is scaled and compared to a defined threshold.
The significant advantage of the proposed method is the implementation of
an automatic algorithm for DWT bearing diagnostics under randomly varying
speed and highly alternating load. Practical applications are provided to showthat the proposed approach is able to achieve reliable failure warning in the
bearing condition monitoring of a DWT.
2014 Meas. Sci. Technol. 25 025004

Non-contact test set-up for aeroelasticity ina rotating turbomachine combining a novel
acoustic excitation system with tip-timing
O Freund, M Montgomery, M Mittelbach and J R Seume

Figure taken fromE Garaio et al 2014
Meas. Sci. Technol. 25
115702A long-stroke horizontal electromagnetic
vibrator for ultralow-frequency vibration
calibration
Wen He, Xufei Zhang, Chunyu Wang, Runjie Shen and Mei Yu
Abstract
A novel long-stroke horizontal electromagnetic vibrator with maximum strokeof 1 m is proposed. To reply to the strong nonlinearity arising from longstroke, a closed double-magnetic circuit with optimal air gap, an electroviscoelastic-suspension device and a track following device are adopted in thevibrator. Also, a compact moving component with a higher first-order natural
frequency is designed to increase the operating frequency of the vibrator.
Finally, experimental results show that the vibrator could output low distortion
acceleration on its working platform from 0.002 Hz to 100 Hz, which verifies thevalidity of the proposed technologies and the applicability of the vibrator for an
ultralow-frequency vibration calibration system.

Abstract
Due to trends in aero-design, aeroelasticity becomes increasingly importantin modern turbomachines. Design requirements of turbomachines leadto the development of high aspect ratio blades and blade integral disc
designs (blisks), which are especially prone to complex modes of vibration.
Therefore, experimental investigations yielding high quality data are requiredfor improving the understanding of aeroelastic effects in turbomachines.
One possibility to achieve high quality data is to excite and measure bladevibrations in turbomachines. The major requirement for blade excitation andblade vibration measurements is to minimize interference with the aeroelastic
effects to be investigated. Thus in this paper, a non-contact—and thus low
interference—experimental set-up for exciting and measuring blade vibrations
is proposed and shown to work. A novel acoustic system excites rotor bladevibrations, which are measured with an optical tip-timing system. By performing
measurements in an axial compressor, the potential of the acoustic excitation
method for investigating aeroelastic effects is explored. The basic principle ofthis method is described and proven through the analysis of blade responses atdifferent acoustic excitation frequencies and at different rotational speeds. To
verify the accuracy of the tip-timing system, amplitudes measured by tip-timing
are compared with strain gage measurements. They are found to agree well.
Two approaches to vary the nodal diameter (ND) of the excited vibration modeby controlling the acoustic excitation are presented. By combining the different
excitable acoustic modes with a phase-lag control, each ND of the investigated30 blade rotor can be excited individually. This feature of the present acoustic
excitation system is of great benefit to aeroelastic investigations and represents
one of the main advantages over other excitation methods proposed in
the past. In future studies, the acoustic excitation method will be used toinvestigate aeroelastic effects in high-speed turbomachines in detail. The
results of these investigations are to be used to improve the aeroelastic designof modern turbomachines.
2014 Meas. Sci. Technol. 25 035008

2014 Meas. Sci. Technol. 25 085901
iopscience.org/mst 		Measurement Science and Technology: Highlights 20143

Winner of 2014 Outstanding Paper Award
Sensors and sensors systems

Accurate 3D shape measurement ofmultiple separate objects with stereo vision

Laser absorption of nitric oxide forthermometry in high-enthalpy air

Hien Kieu, Tongyan Pan, Zhaoyang Wang, Minh Le, Hieu Nguyen andMinh VoR M Spearrin, I A Schultz, J B Jeffries and R K Hanson
Abstract
The design and demonstration of a laser absorption sensor for thermometry
in high-enthalpy air is presented. The sensor exploits the highly temperaturesensitive and largely pressure-independent concentration of nitric oxide in air at
chemical equilibrium. Temperature is thus inferred from an in situ measurementof nascent nitric oxide. The strategy is developed by utilizing a quantum cascadelaser source for access to the strong fundamental absorption band in the
mid-infrared spectrum of nitric oxide. Room temperature measurements in ahigh-pressure static cell validate the suitability of the Voigt lineshape modelto the nitric oxide spectra at high gas densities. Shock-tube experiments
enable calibration of a collision-broadening model for temperatures between
1200–3000 K. Finally, sensor performance is demonstrated in a high-pressureshock tube by measuring temperature behind reflected shock waves for both
fixed-chemistry experiments where nitric oxide is seeded, and for experiments
involving nitric oxide formation in shock-heated mixtures of N2 and O2. Results
show excellent performance of the sensor across a wide range of operating
conditions from 1100–2950 K and at pressures up to 140 atm.
2014 Meas. Sci. Technol. 25 125103

Abstract
3D shape measurement has emerged as a very useful tool in numerous fields
because of its wide and ever-increasing applications. In this paper, we present
a passive, fast and accurate 3D shape measurement technique using stereo
vision approach. The technique first employs a scale-invariant feature transform
algorithm to detect point matches at a number of discrete locations despite thediscontinuities in the images. Then an automated image registration algorithm
is applied to find full-field point matches with subpixel accuracy. After that, the3D shapes of the objects can be reconstructed according to the obtained point
matching and the camera information. The proposed technique is capableof performing a full-field 3D shape measurement with high accuracy even in
the presence of discontinuities and multiple separate regions. The validity isverified by experiments.
2014 Meas. Sci. Technol. 25 035401

A novel pitch evaluation of one-dimensional
gratings based on a cross-correlation filter
Xiaomei Chen and Ludger Koenders

Figure taken from R M Spearrin et al 2014
Meas. Sci. Technol. 25 125103

Spatially resolved acoustic spectroscopy for
rapid imaging of material microstructure andgrain orientation
Richard J Smith, Wenqi Li, Jethro Coulson, Matt Clark, Michael G Somekh
and Steve D Sharples
Abstract
Measuring the grain structure of aerospace materials is very important tounderstand their mechanical properties and in-service performance. Spatiallyresolved acoustic spectroscopy is an acoustic technique utilizing surface
acoustic waves to map the grain structure of a material. When combinedwith measurements in multiple acoustic propagation directions, the grainorientation can be obtained by fitting the velocity surface to a model. The
new instrument presented here can take thousands of acoustic velocity
measurements per second. The spatial and velocity resolution can be adjusted
by simple modification to the system; this is discussed in detail by comparisonof theoretical expectations with experimental data.

Abstract
If one-dimensional (1D), p-period and arbitrarily structured grating positionrelated topographical signals coexist with noise, it is difficult to evaluate thepitch practically using the center-of-gravity (CG) method. The Fourier-transformbased (FT) method is the most precise to evaluate pitches; nevertheless,it cannot give the uniformity of pitches. If a cross-correlation filter—a half
period of sinusoidal waveform sequence (pT period), cross-correlates with thesignals, the noise can be eliminated if pT ≈ p. After cross-correlation filtering,the distance between any two adjacent waveform peaks along the direction
perpendicular to 1D grating lines is one pitch value. The pitch evaluation basedon the cross-correlation filtering together with the detection of the peak's
position is described as the peak detection (PD) method in this paper. The
pitch average and uniformity can be calculated by using the PD method. The
computer simulation has indicated that the average of pitch deviations fromthe true pitch and the pitch variations are less than 0.2% and 0.2% for thesinusoidal and rectangular waveform signals with up to 50% uniform white
noise, less than 0.1% and 1% for the sinusoidal and rectangular waveform
signals and 0.6% and 2.5% for the triangular waveform signal if three waveform
signals are mixed with Gaussian white, binomial and Bernoulli noise up to
50% in standard deviation, one probability and trial probability, respectively.
As examples, a highly oriented pyrolytic graphite (HOPG) with a 0.246 nm
distance between second nearest neighbour atoms and a 1D grating with
3000 nm nominal pitch are measured by a ultra-high vacuum scanningtunneling microscope (UHV STM) and a metrological atomic force microscope(AFM), respectively. After the position-related topographical signals are crosscorrelation filtered, the 0.240 and 3004.11 nm pitches calculated by using the
PD method are very close to the 0.240 and 3003.34 nm results evaluated by
the FT method.
2014 Meas. Sci. Technol. 25 044007

2014 Meas. Sci. Technol. 25 055902

4 Measurement Science and Technology: Highlights 2014

iopscience.org/mst

Winner of 2014 Outstanding Paper Award
Precision measurement

Scanning magnetic tunnel junction
microscope for high-resolution imaging of
remanent magnetization fields
E A Lima, A C Bruno, H R Carvalho and B P Weiss
Abstract
Scanning magnetic microscopy is a new methodology for mapping magnetic
fields with high spatial resolution and field sensitivity. An important goal has
been to develop high-performance instruments that do not require cryogenic
technology due to its high cost, complexity, and limitation on sensor-to-sample
distance. Here we report the development of a low-cost scanning magnetic
microscope based on commercial room-temperature magnetic tunnel junction(MTJ) sensors that typically achieves spatial resolution better than 7 µm. By
comparing different bias and detection schemes, optimal performance wasobtained when biasing the MTJ sensor with a modulated current at 1.0 kHz in a
Wheatstone bridge configuration while using a lock-in amplifier in conjunction
with a low-noise custom-made preamplifier. A precision horizontal (x–y)
scanning stage comprising two coupled nanopositioners controls the positionof the sample and a linear actuator adjusts the sensor-to-sample distance. We
obtained magnetic field sensitivities better than 150 nT/Hz1/2 between 0.1 and
10 Hz, which is a critical frequency range for scanning magnetic microscopy.
This corresponds to a magnetic moment sensitivity of 10–14 A m2, a factor of
100 better than achievable with typical commercial superconducting moment
magnetometers. It also represents an improvement in sensitivity by a factor
between 10 and 30 compared to similar scanning MTJ microscopes basedon conventional bias-detection schemes. To demonstrate the capabilitiesof the instrument, two polished thin sections of representative geologicalsamples were scanned along with a synthetic sample containing magnetic
microparticles. The instrument is usable for a diversity of applications that
require mapping of samples at room temperature to preserve magnetic
properties or viability, including paleomagnetism and rock magnetism,
nondestructive evaluation of materials, and biological assays.

A new general approach for solving theself-calibration problem on large area 2D
ultra-precision coordinate measurement
machines
Peter Ekberg, Lars Stiblert and Lars Mattsson
Abstract
The manufacturing of flat panel displays requires a number of photomasks
for the placement of pixel patterns and supporting transistor arrays. For large
area photomasks, dedicated ultra-precision writers have been developed
for the production of these chromium patterns on glass or quartz plates. The
dimensional tolerances in X and Y for absolute pattern placement on theseplates, with areas measured in square meters, are in the range of 200–300 nm(3σ). To verify these photomasks, 2D ultra-precision coordinate measurement
machines are used having even tighter tolerance requirements. This paper will
present how the world standard metrology tool used for verifying large masks,
the Micronic Mydata MMS15000, is calibrated without any other references
than the wavelength of the interferometers in an extremely well-controlledtemperature environment. This process is called self-calibration and is the
only way to calibrate the metrology tool, as no square-meter-sized large area
2D traceable artifact is available. The only parameter that cannot be foundusing self-calibration is the absolute length scale. To make the MMS15000
traceable, a 1D reference rod, calibrated at a national metrology lab, is used.
The reference plates used in the calibration of the MMS15000 may havesizes up to 1 m2 and a weight of 50 kg. Therefore, standard methods for selfcalibration on a small scale with exact placements cannot be used in the large
area case. A new, more general method had to be developed for the purposeof calibrating the MMS15000. Using this method, it is possible to calibrate
the measurement tool down to an uncertainty level of <90 nm (3σ) over an
area of (0.8 × 0.8) m2. The method used, which is based on the concept of
iteration, does not introduce any more noise than the random noise introducedby the measurements, resulting in the lowest possible noise level that can beachieved by any self-calibration method.
2014 Meas. Sci. Technol. 25 055001

2014 Meas. Sci. Technol. 25 105401

Extending the flash method to measure thethermal diffusivity of semitransparent solids
Agustín Salazar, Arantza Mendioroz, Estibaliz Apiñaniz, Christophe
Pradere, Frédéric Noël and Jean-Christophe Batsale
Abstract
In this work, we extend the classical flash method to retrieve simultaneously
the thermal diffusivity and the optical absorption coefficient of semitransparent
plates. A complete theoretical model that allows calculating the rear surface
temperature rise of the sample has been developed. It takes into consideration
additional effects such as multiple reflections of the heating light beam
inside the sample, heat losses by convection and radiation, transparency ofthe sample to infrared wavelengths and finite duration of the heating pulse.
Measurements performed on calibrated solids, covering a wide range ofabsorption coefficients from transparent to opaque, validate the proposed
method.
Figure taken from E A Lima et al 2014 Meas. Sci. Technol. 25 105401

iopscience.org/mst 		2014 Meas. Sci. Technol. 25 035604

Measurement Science and Technology: Highlights 20145

Capabilities and limitations of the selfcalibration of angle encoders
Ralf D Geckeler, Alfred Link, Michael Krause and Clemens Elster
Abstract
At the Physikalisch-Technische Bundesanstalt (PTB), a self-calibration method
for the fast and precise in situ calibration of angle encoders without recourse
to external reference standards has been developed. It relies on a suitablegeometric arrangement of multiple reading heads which read out the radial
grating of the angle encoder at different angular positions. Fourier-basedalgorithms are used to analyse the measurement differences of pairs of heads
to recover the graduation error of the grating. A comprehensive overview, boththeoretical and experimental, of the capabilities and limitations of the selfcalibration method is presented, including experimental data obtained withthe high-precision primary angle standard of PTB. The evaluation and, where
it is possible, correction of error influences due to lateral shifts of the centre of
the encoder's grating during its rotation, including its eccentricity, the reading
heads' angular positions, and their non-uniform response, are discussed indetail, as well as the resulting uncertainty budget.
2014 Meas. Sci. Technol. 25 055003

An examination of polyvinylidene fluoride
capacitive sensors as ultrasound transducer
for imaging applications

Procedure and reference standard todetermine the structural resolution incoordinate metrology
Jens Illemann, Markus Bartscher, Otto Jusko, Frank Härtig, Ulrich
Neuschaefer-Rube and Klaus Wendt
Abstract
A new procedure and reference standards for specifying the structural
resolution in coordinate metrology traceable to the SI unit the metre areproposed. With the definition of the structural resolution, a significant gap will
be closed to complete ‘acceptance and verification tests’ of the coordinate
measuring systems (CMSs) which are specified in the ISO 10360 series
dealing with tactile sensors, optical sensors, and x-ray computed tomographymeasurement systems (CTs). The proposed new procedure uses reference
standards with circular rounded edges. The idea is to measure the radius ofcurvature on a calibrated round edge structure. From the deviation between
the measured and the calibrated radius, an analogue Gaussian broadeningof the measurement system is determined. This value is a well-defined andeasy-to-apply measure to define the structural resolution for dimensional
measurements. It is applicable to CMSs which are based on different sensing
principles, e.g. tactile, optical and CT systems. On the other hand, it has aphysical meaning similar to the classical optical point-spread function. It
makes it possible to predict which smallest details the CMS is capable ofmeasuring reliably for an arbitrary object shape. The theoretical backgroundof the new procedure is given, an appropriate reference standard is describedand comparative, quantitative measurement data of CMSs featuring different
sensors are shown.
2014 Meas. Sci. Technol. 25 064015

B Reyes-Ramírez, C García-Segundo and A García-Valenzuela
Abstract
We investigate theoretically and experimentally the performance of low-noise
capacitive sensors based on polyvinylidene fluoride (PVDF) piezoelectricfilms to sense water-borne ultrasound signals for their use in photoacoustic
tomography. We derive a mechanical-to-electrical transfer function of apiezoelectric capacitor sensor of infinite lateral dimensions and arbitrary
thickness assuming that an ultrasound wave is normally incident. Then, we
analyse the response for obliquely incident ultrasound waves on sensors oflarge but finite area and derive an expression for the angle dependence of thesensor's response. We also present experimental different measurementswith home-made sensors and compare with our theoretical model. We present
measurements of the sensors’ response to harmonic signals of variablefrequency in the range from 0.5 to 50 MHz and of the angular-dependence
factor at 6 MHz. Additionally, because of the scope of interest in these kinds ofsensors, we also tested the sensors’ response for photoacoustic perturbations.
These are generated by laser pulses from directly impinging on the sensor andfrom ultrasound perturbations produced on neoprene by the same kind of laser
pulses and then travelling through water to the sensor.
2014 Meas. Sci. Technol. 25 055109

Did you know?
Papers to MST are currently accepted on average inthree calendar months from receipt

Reduction of chromatic aberrationinfluences in vertical scanning white-lightinterferometryPeter Lehmann, Peter Kühnhold and Weichang Xie
Abstract
Vertical scanning white-light interferometry (SWLI) is a well-establishedmethod that is widely used in high precision surface topography measurement.
However, SWLI results show characteristic slope-dependent errors due todispersion effects and lateral chromatic aberrations of the optical imaging
system. In this paper, we present methods to characterize these systematic
errors related to dispersion and lateral colour. Lateral colour leads to fielddependent systematic discrepancies of the topography data obtained from theenvelope position of a low-coherence interference signal and the data resulting
from its interference phase. Hence, an erroneous fringe order obtained fromthe envelope position leads to a 2π phase jump and thus to a so-called ghost
step in the measured topography. Our first approach to solve this problem isbased on the measurement of a surface standard of well-known geometry. By
comparison of measurement results related to the envelope position and thephase of SWLI signals, the systematic error is estimated and a numerical error
compensation method is proposed. Both experimental and simulation results
confirm the validity of this numerical method. In addition, using an improved
design of a white-light Michelson interferometer we demonstrate experimentallythat lateral chromatic aberrations and dispersion influences can be reduced
also in a physical way. In this context, a conventional long working distancemicroscope objective is used which was not originally designed for a Michelsoninterference microscope.
2014 Meas. Sci. Technol. 25 065203

6 Measurement Science and Technology: Highlights 2014

iopscience.org/mst

3D reconstruction of hollow parts analyzing
images acquired by a fiberscope
Octavio Icasio-Hernández, José-Joel Gonzalez-Barbosa,Juan B Hurtado-Ramos and Miguel Viliesid-Alonso
Abstract
A modified fiberscope used to reconstruct difficult-to-reach inner structures ispresented. By substituting the fiberscope's original illumination system, we canproject a profile-revealing light line inside the object of study. The light line is
obtained using a sandwiched power light-emitting diode (LED) attached to an
extension arm on the tip of the fiberscope. Profile images from the interior of theobject are then captured by a camera attached to the fiberscope's eyepiece.
Using a series of those images at different positions, the system is capableof generating a 3D reconstruction of the object with submillimeter accuracy.
Also proposed is the use of a combination of known filters to remove thehoneycomb structures produced by the fiberscope and the use of ring gages
to obtain the extrinsic parameters of the camera attached to the fiberscope
and the metrological traceability of the system. Several standard ring diametermeasurements were compared against their certified values to improve theaccuracy of the system. To exemplify an application, a 3D reconstruction of
the interior of a refrigerator duct was conducted. This reconstruction includes
accuracy assessment by comparing the measurements of the system to acoordinate measuring machine. The system, as described, is capable of 3D
reconstruction of the interior of objects with uniform and non-uniform profiles
from 10 to 60 mm in transversal dimensions and a depth of 1000 mm if thematerial of the walls of the object is translucent and allows the detection of
the power LED light from the exterior through the wall. If this is not possible,
we propose the use of a magnetic scale which reduces the working depth to
170 mm. The assessed accuracy is around ±0.15 mm in 2D cross-section
reconstructions and ±1.3 mm in 1D position using a magnetic scale, and ±0.5mm using a CCD camera.
2014 Meas. Sci. Technol. 25 075402

Nondestructive indication of fatigue damage
and residual lifetime in ferromagnetic
construction materials
Ivan Tomáš, Ondřej Kovářík, Gábor Vértesy and Jana Kadlecová
Abstract
A new revolutionary attitude toward investigation of fatigue damage in cyclicallyloaded steel samples is reported. The measurement is based on the methodof magnetic adaptive testing, which–in contrast to traditional magnetic
hysteresis investigations–picks up the relevant information from systematic
measurement and evaluation of whole minor magnetic hysteresis loops andtheir derivatives. Satisfactory correlations between nondestructively measured
magnetic descriptors and actual lifetime of the fatigued material were found.
The presented method is able to serve as a powerful tool for indication ofchanges, which occur in the structure of the inspected objects during theirindustrial service lifetime, as long as they are manufactured from ferromagnetic
materials.
2014 Meas. Sci. Technol. 25 065601

Multiple wavelength interferometry for
distance measurements of moving objects
with nanometer uncertainty
R Kuschmierz, J Czarske and A Fischer
Abstract
Optical measurement techniques offer great opportunities in diverse
applications, such as lathe monitoring and microfluidics. Doppler-based
interferometric techniques enable simultaneous measurement of thelateral velocity and axial distance of a moving object. However, there is acomplementarity between the unambiguous axial measurement range andthe uncertainty of the distance. Therefore, we present an extended sensor
setup, which provides an unambiguous axial measurement range of 1 mm
while achieving uncertainties below 100 nm. Measurements at a calibration
system are performed. When using a pinhole for emulating a single scattering
particle, the tumbling motion of the rotating object is resolved with a distanceuncertainty of 50 nm. For measurements at the rough surface, the distanceuncertainty amounts to 280 nm due to a lower signal-to-noise ratio. Bothexperimental results are close to the respective Cramér–Rao bound, which isderived analytically for both surface and single particle measurements.
2014 Meas. Sci. Technol. 25 085202

Design and testing of a four-probe opticalsensor head for three-axis surface encoderwith a mosaic scale grating
Yuki Shimizu, Takeshi Ito, Xinghui Li, WooJae Kim and Wei Gao
Abstract
This paper presents a design study of a four-probe optical sensor head fora three-axis surface encoder with a mosaic scale grating. As the mosaic
scale grating, multiple two-dimensional reflective-type scale gratings arealigned in a matrix on a plane so that measurement ranges of the three-axis
surface encoder along the X- and Y-axes can be extended. An optical layout
for a four-probe unit, which consists of a laser diode and two beam splitters,
was designed based on geometrical optics so that four probes aligned in
the matrix can be generated. The designed four-probe unit was integrated
into the optical sensor head of the three-axis surface encoder. Interference
signals generated by the superimposition of diffraction beams from the XY
gratings were utilized in the three-axis surface encoder so that the translational
displacement motions of the mosaic scale grating along the X-, Y- and Z-axes
can be detected simultaneously by each probe in the four probes. Experiments
were carried out to verify the feasibility of both the designed four-probe
optical sensor head and the proposed concept of the mosaic scale grating for
expanding the measurement range of the three-axis surface encoder along theX- and Y-directional primary axes of motion. Measurement sensitivity of eachprobe was compared, and its compensation was carried out by linear matrix
calculations. Measurement resolution and nonlinearity of each probe werealso investigated. In addition, XYZ-directional translational motions of a linear
stage when a long-range translational motion along the X-axis was given to themosaic scale grating were measured by stitching the measured results by thefour probes.
2014 Meas. Sci. Technol. 25 094002

iopscience.org/mst 		Measurement Science and Technology: Highlights 20147

Array-based satellite phase bias sensing:theory and GPS/BeiDou/QZSS results
A Khodabandeh and P J G Teunissen
Abstract
Single-receiver integer ambiguity resolution (IAR) is a measurement conceptthat makes use of network-derived non-integer satellite phase biases (SPBs),
among other corrections, to recover and resolve the integer ambiguities of thecarrier-phase data of a single GNSS receiver. If it is realized, the very precise
integer ambiguity-resolved carrier-phase data would then contribute to theestimation of the receiver's position, thus making (near) real-time precise point
positioning feasible. Proper definition and determination of the SPBs take aleading part in developing the idea of single-receiver IAR. In this contribution,
the concept of array-based between-satellite single-differenced (SD) SPB
determination is introduced, which is aimed to reduce the code-dominatedprecision of the SD-SPB corrections. The underlying model is realized by giving
the role of the local reference network to an array of antennas, mounted on rigid
platforms, that are separated by short distances so that the same ionosphericdelay is assumed to be experienced by all the antennas. To that end, aclosed-form expression of the array-aided SD-SPB corrections is presented,
thereby proposing a simple strategy to compute the SD-SPBs. After resolving
double-differenced ambiguities of the array's data, the variance of the SD-SPB
corrections is shown to be reduced by a factor equal to the number of antennas.
This improvement in precision is also affirmed by numerical results of the three
GNSSs GPS, BeiDou and QZSS. Experimental results demonstrate that the
integer-recovered ambiguities converge to integers faster, upon increasing thenumber of antennas aiding the SD-SPB corrections.
2014 Meas. Sci. Technol. 25 095801

Knock detection in spark ignition engines
using a nonlinear wavelet transform of theengine cylinder head vibration signal
Ning Li, Jianguo Yang, Rui Zhou and Qingsheng Wang
Abstract
This paper reports an investigation of knock detection in SI engines using
a nonlinear wavelet transform based on the engine cylinder head vibration
signals. The nonlinear wavelet transform employed in the current research isconstructed by the redundant lifting scheme with an update-first framework,
which has the ability to select an optimal wavelet function for each transform
sample. The feasibility of applying a nonlinear wavelet transform to detectknock signatures from the vibration signals of the cylinder head is studied.
The experimental results verify that the proposed method is capable ofdetecting knock signatures, even during the initial stages. More importantly, it
is found that knock in each cylinder of a multi-cylinder gasoline engine can bedetected using just one vibration sensor. Consequently, this is a simple andcost-effective way for knock detection in SI engines. Derived from the above
method, we have developed a novel knock intensity factor and investigated therelevance of the proposed criterion for characterizing different levels of knock.
2014 Meas. Sci. Technol. 25 115002

Did you know?
MST’s rigorous peer review process means thatfewer than one in three papers submitted to thejournal are accepted for publication
8 Measurement Science and Technology: Highlights 2014

Particle image velocimetry correlation signalto-noise ratio metrics and measurement
uncertainty quantification
Zhenyu Xue, John J Charonko and Pavlos P Vlachos
Abstract
In particle image velocimetry (PIV) the measurement signal is containedin the recorded intensity of the particle image pattern superimposed on avariety of noise sources. The signal-to-noise-ratio (SNR) strength governs theresulting PIV cross correlation and ultimately the accuracy and uncertainty of
the resulting PIV measurement. Hence we posit that correlation SNR metrics
calculated from the correlation plane can be used to quantify the quality of
the correlation and the resulting uncertainty of an individual measurement. In
this paper we extend the original work by Charonko and Vlachos and present
a framework for evaluating the correlation SNR using a set of different metrics,
which in turn are used to develop models for uncertainty estimation. Several
corrections have been applied in this work. The SNR metrics and corresponding
models presented herein are expanded to be applicable to both standard
and filtered correlations by applying a subtraction of the minimum correlation
value to remove the effect of the background image noise. In addition, thenotion of a ‘valid’ measurement is redefined with respect to the correlation
peak width in order to be consistent with uncertainty quantification principles
and distinct from an ‘outlier’ measurement. Finally the type and significanceof the error distribution function is investigated. These advancements lead tomore robust and reliable uncertainty estimation models compared with theoriginal work by Charonko and Vlachos. The models are tested against bothsynthetic benchmark data as well as experimental measurements. In thiswork, U68.5 uncertainties are estimated at the 68.5% confidence level while
U95 uncertainties are estimated at 95% confidence level. For all cases theresulting calculated coverage factors approximate the expected theoreticalconfidence intervals, thus demonstrating the applicability of these new models
for estimation of uncertainty for individual PIV measurements.
2014 Meas. Sci. Technol. 25 115301

Underground localization using dual
magnetic field sequence measurement andpose graph SLAM for directional drilling
Byeolteo Park and Hyun Myung
Abstract
With the development of unconventional gas, the technology of directional
drilling has become more advanced. Underground localization is the key
technique of directional drilling for real-time path following and system
control. However, there are problems such as vibration, disconnection withexternal infrastructure, and magnetic field distortion. Conventional methods
cannot solve these problems in real time or in various environments. In thispaper, a novel underground localization algorithm using a re-measurementof the sequence of the magnetic field and pose graph SLAM (simultaneous
localization and mapping) is introduced. The proposed algorithm exploits theproperty of the drilling system that the body passes through the previous pass.
By comparing the recorded measurement from one magnetic sensor and thecurrent re-measurement from another magnetic sensor, the proposed algorithm
predicts the pose of the drilling system. The performance of the algorithm isvalidated through simulations and experiments.
2014 Meas. Sci. Technol. 25 125101

iopscience.org/mst