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  • 1.
    Belyayev, Serhiy
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. Lviv Center of Institute of Space Research, NASU/NSAU, S-A Naukova St., Lviv, Ukraine.
    Ivchenko, Nickolay
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Digital fluxgate magnetometer: design notes2015In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 26, no 12, article id 125901Article in journal (Refereed)
    Abstract [en]

    We presented an approach to understanding the performance of a fully digital fluxgate magnetometer. All elements of the design are important for the performance of the instrument, and the presence of the digital feed-back loop introduces certain peculiarities affecting the noise and dynamic performance of the instrument. Ultimately, the quantisation noise of the digital to analogue converter is found to dominate the noise of the current design, although noise shaping alleviates its effect to some extent. An example of magnetometer measurements on board a sounding rocket is presented, and ways to further improve the performance of the instrument are discussed.

  • 2.
    Belyayev, Serhiy
    et al.
    KTH. Lviv Center of Institute of Space Research, NASU/SSAU, Ukraine.
    Ivchenko, Nickolay
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Effect of second harmonic in pulse-width-modulation-based DAC for feedback of digital fluxgate magnetometer2018In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 29, no 4, article id 045008Article in journal (Refereed)
    Abstract [en]

    Digital fluxgate magnetometers employ processing of the measured pickup signal to produce the value of the compensation current. Using pulse-width modulation with filtering for digital to analog conversion is a convenient approach, but it can introduce an intrinsic source of nonlinearity, which we discuss in this design note. A code shift of one least significant bit changes the second harmonic content of the pulse train, which feeds into the pick-up signal chain despite the heavy filtering. This effect produces a code-dependent nonlinearity. This nonlinearity can be overcome by the specific design of the timing of the pulse train signal. The second harmonic is suppressed if the first and third quarters of the excitation period pulse train are repeated in the second and fourth quarters. We demonstrate this principle on a digital magnetometer, achieving a magnetometer noise level corresponding to that of the sensor itself. 

  • 3.
    Binder, Christian
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. Scania CV AB.
    Henrik, Feuk
    Lund University.
    Richter, Mattias
    Lund University.
    Phosphor Thermometry for In-Cylinder Surface Temperature Measurements in Diesel Engines2019In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501Article in journal (Other academic)
    Abstract [en]

    Surface temperature measurements in technically relevant applications can be very  hallenging and yet of great importance. Phosphor thermometry is a temperature measurement technique that has previously been employed in technically relevant applications to obtain surface temperature. The technique is based on temperature-dependent changes in a phosphor’s luminescence. To improve the accuracy and precision of temperature measurements with this technique, the present study considers, by way of example, the impact of conditions inside the cylinder of a diesel engine on decay time based phosphor thermometry. After an initial, general assessment of the effect of prevailing measurement conditions, this research investigates errors caused by soot luminosity, extinction, signal trapping and changes of phosphors’ luminescence properties due to exposure to the harsh environment. Furthermore, preferable properties of phosphors which are suitable for in-cylinder temperature measurements are discussed. 16 phosphors are evaluated, including four which – to the authors’ knowledge –have previously not been used in thermometry. Results indicate that errors due to photocathode bleaching, extinction, signal trapping and changes of luminescence properties may cause an erroneous temperature evaluation with temperature errors in the order of serval tens of Kelvin.

  • 4.
    Bitaraf Haghighi, Ehsan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Nikkam, Nader
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Saleemi, Mohsin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Behi, Mohammadreza
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Mirmohammadi, Seyed Aliakbar
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Poth, H.
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Shelf stability of nanofluids and its effect on thermal conductivity and viscosity2013In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 24, no 10, p. 105301-Article in journal (Refereed)
    Abstract [en]

    This study proposes a method and apparatus to estimate shelf stability of nanofluids. Nanofluids are fabricated by dispersion of solid nanoparticles in base fluids, and shelf stability is a key issue for many practical applications of these fluids. In this study, shelf stability is evaluated by measuring the weight of settled solid particles on a suspended tray in a colloid versus time and correlated with the performance change of some nanofluid systems. The effects of solid particle concentration and bath sonication time were investigated for selected nanofluids. The results show the applicability of this simple method and the apparatus to evaluate nanofluid shelf stability. Furthermore, it shows that Stokes' law is not valid for determining the settling time of the tested nanoparticles probably due to their complicated shape and presence of surface modifiers. The effect of shelf stability on thermal conductivity and viscosity was illustrated for some nanofluids. Experimental results show that water-based Al2O3 nanofluids have quite good shelf stability and can be good candidates for industrial applications.

  • 5.
    Buendia, Ruben
    et al.
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Gil-Pita, Roberto
    Department of Theory of the Signal and Communications, University of Alcala, Madrid, Spain.
    Experimental validation of a method for removing the capacitive leakage artifact from electrical bioimpedance spectroscopy measurements2010In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 21, no 11Article in journal (Refereed)
    Abstract [en]

    Often when performing electrical bioimpedance (EBI) spectroscopy measurements, the obtained EBI data present a hook-like deviation, which is most noticeable at high frequencies in the impedance plane. The deviation is due to a capacitive leakage effect caused by the presence of stray capacitances. In addition to the data deviation being remarkably noticeable at high frequencies in the phase and the reactance spectra, the measured EBI is also altered in the resistance and the modulus. If this EBI data deviation is not properly removed, it interferes with subsequent data analysis processes, especially with Cole model-based analyses. In other words, to perform any accurate analysis of the EBI spectroscopy data, the hook deviation must be properly removed. Td compensation is a method used to compensate the hook deviation present in EBI data; it consists of multiplying the obtained spectrum, Z meas (ω), by a complex exponential in the form of exp(–jωTd). Although the method is well known and accepted, Td compensation cannot entirely correct the hook-like deviation; moreover, it lacks solid scientific grounds. In this work, the Td compensation method is revisited, and it is shown that it should not be used to correct the effect of a capacitive leakage; furthermore, a more developed approach for correcting the hook deviation caused by the capacitive leakage is proposed. The method includes a novel correcting expression and a process for selecting the proper values of expressions that are complex and frequency dependent. The correctness of the novel method is validated with the experimental data obtained from measurements from three different EBI applications. The obtained results confirm the sufficiency and feasibility of the correcting method.

  • 6. Chrysostomou, Dimitrios
    et al.
    Gasteratos, Antonios
    Nalpantidis, Lazaros
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP. KTH, School of Computer Science and Communication (CSC), Centres, Centre for Autonomous Systems, CAS.
    Sirakoulis, Georgios C.
    Multi-view 3D scene reconstruction using ant colony optimization techniques2012In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 23, no 11, p. 114002-Article in journal (Refereed)
    Abstract [en]

    This paper presents a new method performing high-quality 3D object reconstruction of complex shapes derived from multiple, calibrated photographs of the same scene. The novelty of this research is found in two basic elements, namely: (i) a novel voxel dissimilarity measure, which accommodates the elimination of the lighting variations of the models and (ii) the use of an ant colony approach for further refinement of the final 3D models. The proposed reconstruction procedure employs a volumetric method based on a novel projection test for the production of a visual hull. While the presented algorithm shares certain aspects with the space carving algorithm, it is, nevertheless, first enhanced with the lightness compensating image comparison method, and then refined using ant colony optimization. The algorithm is fast, computationally simple and results in accurate representations of the input scenes. In addition, compared to previous publications, the particular nature of the proposed algorithm allows accurate 3D volumetric measurements under demanding lighting environmental conditions, due to the fact that it can cope with uneven light scenes, resulting from the characteristics of the voxel dissimilarity measure applied. Besides, the intelligent behavior of the ant colony framework provides the opportunity to formulate the process as a combinatorial optimization problem, which can then be solved by means of a colony of cooperating artificial ants, resulting in very promising results. The method is validated with several real datasets, along with qualitative comparisons with other state-of-the-art 3D reconstruction techniques, following the Middlebury benchmark.

  • 7. Corman, Thierry
    et al.
    Enoksson, Peter
    Noren, Kjell
    Stemme, Göran
    KTH, Superseded Departments, Signals, Sensors and Systems.
    A low-pressure encapsulated resonant fluid density sensor with feedback control electronics2000In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 11, no 3, p. 205-211Article in journal (Refereed)
    Abstract [en]

    In this paper we present a fully low-pressure encapsulated and closed-loop operated resonant fluid density sensor. The device consists of a tube in silicon, which is vibrating in a selected balanced torsion mode. The resonance frequency changes with the density of the fluid in the tube due to the change of the inertial mass of the vibrating system. The sensor is fabricated and encapsulated at wafer level using silicon micromachining techniques. The encapsulation is performed by anodically bonding the silicon densitometer in vacuum between two glass lids with metal electrodes for electrostatic excitation and capacitive detection. The sample volume is only 0.035 mi and the size of the encapsulated device is 14 mm x 23 mm x 1.85 mm. The measurements were performed using a novel excitation and detection technique based on discontinuous, 'burst' excitation. This principle enabled us to eliminate the electrical crosstalk between excitation and detection. The electrodes could be placed on top of the glass lids without using electrical feedthroughs, and a cavity gap of 100 mu m could be formed between the recessed glass lid surface and the silicon tube to reduce squeeze-film damping. The closed-loop 'burst' technology enabled us to make continuous measurements of fluid densities. The sensor showed high density sensitivities of the order of -200 ppm (kg m(-3))(-1), a high mechanical e-factor of 3400 for air in the tube and low temperature sensitivities of -29 ppm degrees C-1 in the range 20-100 degrees C.

  • 8. Dörr, H.
    et al.
    Koturbash, Taras
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. GasQuaL AB, Brinellvägen 68, 114 28 Stockholm, Sweden.
    Kutcherov, Vladimir G.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Review of impacts of gas qualities with regard to quality determination and energy metering of natural gas2019In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 30, no 2, article id 022001Article in journal (Refereed)
    Abstract [en]

    Diversification of gas supply via the liberalization of the gas trade, the discovery of new fossil gas sources, and the increasing use of renewable gases, are favoring pronounced and more frequent fluctuations in gas quality. The knowledge of gas quality is crucial for custody transfer, and safe, efficient and low-emission operation of gas-driven processes. The onsite measurement of gas quality by the operators of gas production facilities, gas grids, gas storage and gas utilization facilities is an emerging requirement. This paper describes several different approaches for determining gas quality by direct, indirect and inferential methods based on the physicochemical properties of gas. Special emphasis is devoted to a discussion on the miniaturization of gas quality sensors and the incorporation of hydrogen detection and measurement into these sensors, due to potential hydrogen admixture to natural gas. In addition, an overview and analysis of the regulatory and normative requirements for gas quality measurements are presented. Furthermore, an overview of gas quality measurement devices and sensors, recent developments as well as challenges and benefits associated with gas quality measurement instrumentation, are provided.

  • 9.
    Ekberg, Peter
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Daemi, Bita
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Mattsson, Lars
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    3D precision measurements of meter sized surfaces using low cost illumination and camera techniques2017In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 28, no 4, article id 045403Article in journal (Refereed)
    Abstract [en]

    Using dedicated stereo camera systems and structured light is a well-known method for measuring the 3D shape of large surfaces. However the problem is not trivial when high accuracy, in the range of few tens of microns, is needed. Many error sources need to be handled carefully in order to obtain high quality results. In this study, we present a measurement method based on low-cost camera and illumination solutions combined with high-precision image analysis and a new approach in camera calibration and 3D reconstruction. The setup consists of two ordinary digital cameras and a Gobo projector as a structured light source. A matrix of dots is projected onto the target area. The two cameras capture the images of the projected pattern on the object. The images are processed by advanced subpixel resolution algorithms prior to the application of the 3D reconstruction technique. The strength of the method lays in a different approach for calibration, 3D reconstruction, and high-precision image analysis algorithms. Using a 10 mm pitch pattern of the light dots, the method is capable of reconstructing the 3D shape of surfaces. The precision (1 sigma repeatability) in the measurements is < 10 mu m over a volume of 60 x 50 x 10 cm(3) at a hardware cost of similar to 2% of available advanced measurement techniques. The expanded uncertainty (95% confidence level) is estimated to be 83 mu m, with the largest uncertainty contribution coming from the absolute length of the metal ruler used as reference.

  • 10.
    Ekberg, Peter
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Mattsson, Lars
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Traceable X,Y self-calibration at single nm level of an optical microscope used for coherence scanning interferometry2018In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 29, no 3, article id 035005Article in journal (Refereed)
    Abstract [en]

    Coherence scanning interferometry used in optical profilers are typically good for Z-calibration at nm-levels, but the X,Y accuracy is often left without further notice than typical resolution limits of the optics, i.e. of the order of similar to 1 mu m. For the calibration of metrology tools we rely on traceable artefacts, e.g. gauge blocks for traditional coordinate measurement machines, and lithographically mask made artefacts for microscope calibrations. In situations where the repeatability and accuracy of the measurement tool is much better than the uncertainty of the traceable artefact, we are bound to specify the uncertainty based on the calibration artefact rather than on the measurement tool. This is a big drawback as the specified uncertainty of a calibrated measurement may shrink the available manufacturing tolerance. To improve the uncertainty in X, Y we can use self-calibration. Then, we do not need to know anything more than that the artefact contains a pattern with some nominal grid. This also gives the opportunity to manufacture the artefact in-house, rather than buying a calibrated and expensive artefact. The self-calibration approach we present here is based on an iteration algorithm, rather than the traditional mathematical inversion, and it leads to much more relaxed constrains on the input measurements. In this paper we show how the X, Y errors, primarily optical distortions, within the field of view (FOV) of an optical coherence scanning interferometry microscope, can be reduced with a large factor. By self-calibration we achieve an X, Y consistency in the 175 x 175 mu m(2) FOV of similar to 2.3 nm (1 sigma) using the 50x objective. Besides the calibrated coordinate X, Y system of the microscope we also receive, as a bonus, the absolute positions of the pattern in the artefact with a combined uncertainty of 6 nm (1s) by relying on a traceable 1D linear measurement of a twin artefact at NIST.

  • 11.
    Ekberg, Peter
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Metrology and Optics. Micronic Laser Systems, Stockholm, Sweden.
    Stiblert, Lars
    Micronic Laser Systems, Stockholm, Sweden.
    Mattsson, Lars
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Metrology and Optics.
    A Large-area ultra-precision 2D geometrical measurement technique based on statistical random phase detection2012In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 23, no 3Article in journal (Refereed)
    Abstract [en]

    The manufacturing of high-quality chrome masks used in the display industry for the manufacturing of liquid crystals, organic light emission diodes and other display devices would not be possible without high-precision large-area metrology. In contrast to the semiconductor industry where 6' masks are most common, the quartz glass masks for the manufacturing of large area TVs can have sizes of up to 1.6 x 1.8 m(2). Besides the large area, there are demands of sub-micrometer accuracy in 'registration', i.e. absolute dimensional measurements and nanometer requirements for 'overlay', i.e. repeatability. The technique for making such precise measurements on large masks is one of the most challenging tasks in dimensional metrology today. This paper presents a new approach to two-dimensional (2D) ultra-precision measurements based on random sampling. The technique was recently presented for ultra-precise one-dimensional (1D) measurement. The 1D method relies on timing the scanning of a focused laser beam 200 mu m in the Y-direction from an interferometrically determined reference position. This microsweep is controlled by an acousto-optical deflector. By letting the microsweep scan from random X-positions, we can build XY-recordings through a time-to-space conversion that gives very precise maps of the feature edges of the masks. The method differs a lot from ordinary image processing methods using CCD or CMOS sensors for capturing images in the spatial domain. We use events grabbed by a single detector in the time domain in both the X-and Y-directions. After a simple scaling, we get precise and repeatable spatial information. Thanks to the extremely linear microsweep and its precise power control, spatial and intensity distortions, common in ordinary image processing systems using 2D optics and 2D sensors, can be practically eliminated. Our 2D method has proved to give a standard deviation in repeatability of less than 4 nm (1 sigma) in both the X-and Y-directions over an area of approximately 0.8 x 0.8 m(2). Only feature edges are recorded, so all irrelevant information in areas containing constant intensity are filtered out already by the hardware. This relaxes the demands and complexity of the data channel dramatically compared to conventional imaging systems.

  • 12.
    Ekberg, Peter
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Metrology and Optics.
    Stiblert, Lars
    Micronic Laser Systems, Stockholm, Sweden.
    Mattsson, Lars
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Metrology and Optics.
    A new general approach for solving the self-calibration problem on large area 2D ultra-precision coordinate measurement machines2014In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 25, no 5, p. 055001-Article in journal (Refereed)
    Abstract [en]

    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 these plates, with areas measured in square meters, are in the range of 200-300 nm (3 sigma). 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-controlled temperature 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 found using 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 have sizes up to 1 m(2) and a weight of 50 kg. Therefore, standard methods for self-calibration 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 purpose of calibrating the MMS15000. Using this method, it is possible to calibrate the measurement tool down to an uncertainty level of <90 nm (3 sigma) over an area of (0.8 x 0.8) m(2). The method used, which is based on the concept of iteration, does not introduce any more noise than the random noise introduced by the measurements, resulting in the lowest possible noise level that can be achieved by any self-calibration method.

  • 13.
    Ekberg, Peter
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Metrology and Optics.
    Stiblert, Lars
    Micronic Laser Systems, Stockholm, Sweden.
    Mattsson, Lars
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Metrology and Optics.
    Ultra-precision geometrical measurement technique based on a statistical random phase clock combined with acoustic-optical deflection2010In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 21, no 12, p. 125103-Article in journal (Refereed)
    Abstract [en]

    Mask writers and large area measurements systems are key systems for production of large liquid crystal displays (LCD) and image devices. With position tolerances in the sub-mu m range over square meter sized masks, the metrology challenges are indeed demanding. Most systems used for this type of measurement rely on a microscope camera imaging system, provided with a charge coupled device, a complementary metal-oxide-semiconductor sensor or a time delay and integration sensor to transform the optical image to a digital gray-level image. From this image, processing algorithms are used to extract information such as location of edges. The drawback of this technique is the vast amount of data captured but never used. This paper presents a new approach for ultra-high-precision lateral measurement at nm-levels of chrome/glass patterns separated by centimeters, so called registration marks, on masks used for the LCD manufacturing. Registration specifications demand a positioning accuracy <200 nm and critical dimensions, i.e. chrome line widths, which need to be accurate in the 80 nm range. This accuracy has to be achieved on glass masks of 2.4 x 1.6 m(2) size. Our new measurement method is based on nm-precise lateral scanning of a focused laser beam combined with statistical random phase sampling of the reflected signal. The precise scanning is based on an extremely accurate time measuring device controlling an acousto optic deflector crystal. The method has been successfully applied in measuring the 4 mu m pitch of reference gratings at standard deviations sigma of 0.5 nm and registration marks separated by several cm at standard deviations of 23 nm.

  • 14.
    Ekberg, Peter
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Metrology and Optics.
    Stiblert, Lars
    Micronic Laser Systems, Stockholm, Sweden.
    Mattsson, Lars
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Metrology and Optics.
    Z-correction, a method for achieving ultraprecise self-calibration on large area coordinate measurement machines for photomasks2014In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 25, no 5, p. 055002-Article in journal (Refereed)
    Abstract [en]

    High-quality photomasks are a prerequisite for the production of flat panel TVs, tablets and other kinds of high-resolution displays. During the past years, the resolution demand has become more and more accelerated, and today, the high-definition standard HD, 1920 x 1080 pixels(2), is well established, and already the next-generation so-called ultra-high-definition UHD or 4K display is entering the market. Highly advanced mask writers are used to produce the photomasks needed for the production of such displays. The dimensional tolerance in X and Y on absolute pattern placement on these photomasks, with sizes of square meters, has been in the range of 200-300 nm (3 sigma), but is now on the way to be <150 nm (3 sigma). To verify these photomasks, 2D ultra-precision coordinate measurement machines are used with even tighter tolerance requirements. The metrology tool MMS15000 is today the world standard tool used for the verification of large area photomasks. This paper will present a method called Z-correction that has been developed for the purpose of improving the absolute X, Y placement accuracy of features on the photomask in the writing process. However, Z-correction is also a prerequisite for achieving X and Y uncertainty levels <90 nm (3 sigma) in the self-calibration process of the MMS15000 stage area of 1.4 x 1.5 m(2). When talking of uncertainty specifications below 200 nm (3 sigma) of such a large area, the calibration object used, here an 8-16 mmthick quartz plate of size approximately a square meter, cannot be treated as a rigid body. The reason for this is that the absolute shape of the plate will be affected by gravity and will therefore not be the same at different places on the measurement machine stage when it is used in the self-calibration process. This mechanical deformation will stretch or compress the top surface (i.e. the image side) of the plate where the pattern resides, and therefore spatially deform the mask pattern in the X- and Y-directions. Errors due to this deformation can easily be several hundred nanometers. When Z-correction is used in the writer, it is also possible to relax the flatness demand of the photomask backside, leading to reduced manufacturing costs of the plates.

  • 15.
    Ford, C. L.
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Winroth, Marcus
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Alfredsson, P. Henrik
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Development of a pressure based vortex-shedding meter: measuring unsteady mass-flow in variable density gases2016In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 27, no 8, article id 085901Article in journal (Refereed)
    Abstract [en]

    An entirely pressure-based vortex-shedding meter has been designed for use in practical time-dependent flows. The meter is capable of measuring mass-flow rate in variable density gases in spite of the fact that fluid temperature is not directly measured. Unlike other vortex meters, a pressure based meter is incredibly robust and may be used in industrial type flows; an environment wholly unsuitable for hot-wires for example. The meter has been tested in a number of static and dynamic flow cases, across a range of mass-flow rates and pressures. The accuracy of the meter is typically better than about 3% in a static flow and resolves the fluctuating mass-flow with an accuracy that is better than or equivalent to a hot-wire method.

  • 16. Forslund, Åke
    et al.
    Belyayev, Serhiy
    Ivchenko, Nickolay V.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Olsson, Göran
    Edberg, Terry
    Miniaturized digital fluxgate magnetometer for small spacecraft applications2008In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 19, no 1Article in journal (Refereed)
    Abstract [en]

    A novel design of an Earth field digital fluxgate magnetometer is presented, the small magnetometer in low-mass experiment (SMILE). The combination of a number of new techniques results in significant miniaturization of both sensor and electronics. The design uses a sensor with volume compensation, combining three dual rod cores in a Macor (R) cube with the side dimension of 20 mm. Use of volume compensation provides high geometrical stability of the axes and improved performance compared to component compensated sensors. The sensor is operated at an excitation frequency of 8 kHz. Most of the instrument functionality is combined in a digital signal processing core, implemented in a field programmable gate array (FPGA). The pick-up signal is digitized after amplification and filtering, and values of compensation currents for each of the axes are determined by a digital correlation algorithm, equivalent to a matched filter, and are fed to a hybrid pulse-width modulation/delta-sigma digital-to-analogue converter driving the currents through the compensation coils. Using digital design makes the instrument very flexible, reduces power consumption and opens possibilities for the customization of the operation modes. The current implementation of the design is based on commercial off-the-shelf components. A calibration of the SMILE instrument was carried out at the Nurmijarvi Geophysical Observatory, showing high linearity (within 6 nT on the whole +/- 50 mu T scale), good orthogonality (22 arcmin) and very good temperature stability of the axes.

  • 17. Gren, P.
    et al.
    Tatar, K.
    Granström, J.
    Molin, N. E.
    Jansson, Erik V.
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH.
    Laser vibrometry measurements of vibration and sound fields of a bowed violin2006In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 17, no 4, p. 635-644Article in journal (Refereed)
    Abstract [en]

    Laser vibrometry measurements on a bowed violin are performed. A rotating disc apparatus, acting as a violin bow, is developed. It produces a continuous, long, repeatable, multi-frequency sound from the instrument that imitates the real bow-string interaction for a 'very long bow'. What mainly differs is that the back and forward motion of the real bow is replaced by the rotating motion with constant velocity of the disc and constant bowing force (bowing pressure). This procedure is repeatable. It is long lasting and allows laser vibrometry techniques to be used, which measure forced vibrations by bowing at all excited frequencies simultaneously. A chain of interacting parts of the played violin is studied: the string, the bridge and the plates as well as the emitted sound field. A description of the mechanics and the sound production of the bowed violin is given, i.e. the production chain from the bowed string to the produced tone.

  • 18.
    Laurantzon, Fredrik
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics. KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO.
    Örlü, Ramis
    KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO.
    Segalini, Antonio
    KTH, School of Engineering Sciences (SCI), Mechanics, Stability, Transition and Control. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Alfredsson, P. Henrik
    KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO.
    Time-resolved measurements with a vortex flowmeter in a pulsating turbulent flow using wavelet analysis2010In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 21, no 12, p. 123001-Article in journal (Refereed)
    Abstract [en]

    Vortex flowmeters are commonly employed in technical applications and are obtainable in a variety of commercially available types. However their robustness and accuracy can easily be impaired by environmental conditions, such as inflow disturbances and/or pulsating conditions. Various post-processing techniques of the vortex signal have been used, but all of these methods are so far targeted on obtaining an improved estimate of the time-averaged bulk velocity. Here, on the other hand, we propose, based on wavelet analysis, a straightforward way to utilize the signal from a vortex shedder to extract the time-resolved and thereby the phase-averaged velocity under pulsatile flow conditions. The method was verified with hot-wire and laser Doppler velocimetry measurements.

  • 19.
    Nalpantidis, Lazaros
    et al.
    Production and Management Engineering Dept., Democritus University of Thrace, Greece.
    Sirakoulis, Georgios Ch.
    Electrical and Computer Engineering Dept., Democritus University of Thrace, Greece.
    Gasteratos, Antonios
    Production and Management Engineering Dept., Democritus University of Thrace, Greece.
    Non-probabilistic cellular automata-enhanced stereo vision simultaneous localization and mapping2011In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 22, no 11, p. 114027-Article in journal (Refereed)
    Abstract [en]

    In this paper, a visual non-probabilistic simultaneous localization and mapping (SLAM) algorithm suitable for area measurement applications is proposed. The algorithm uses stereo vision images as its only input and processes them calculating the depth of the scenery, detecting occupied areas and progressively building a map of the environment. The stereo vision-based SLAM algorithm embodies a stereo correspondence algorithm that is tolerant to illumination differentiations, the robust scale- and rotation-invariant feature detection and matching speeded-up robust features method, a computationally effective v-disparity image calculation scheme, a novel map-merging module, as well as a sophisticated cellular automata-based enhancement stage. A moving robot equipped with a stereo camera has been used to gather image sequences and the system has autonomously mapped and measured two different indoor areas.

  • 20.
    Nilsson, Bruno
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Tilert, Dan
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Temun, Attila
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Carlsson, Torgny E.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Mattsson, Lars
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Fast four-channel fibre-optic displacement sensor for measuring impact waves at low cost2006In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 17, no 5, p. 1162-1166Article in journal (Refereed)
    Abstract [en]

    We have developed a fast four-channel fibre-optic sensor for measuring dynamic surface displacements caused by shock waves. Light from an LED emitter is sent through a plastic fibre and reflected from the surface back into the fibre. The intensity of the reflected light gives the distance to the surface unambigously. Based on simple principles and utilizing inexpensive components, micrometre and microsecond resolution is achieved at lower cost and with easier usage than for interferometric methods and with better reliability than an accelerometer. The sensor is comparatively easy to set up. It is battery operated for reduced sensitivity to electromagnetic interference. The design of the fibre probe facilitates access in narrow and hostile environments.

  • 21. Pal, S.
    et al.
    Mandal, J.
    Sun, T.
    Grattan, K. T. V.
    Fokine, Michael
    Carlsson, F.
    Fonjallaz, P. Y.
    Wade, S. A.
    Collins, S. F.
    Characteristics of potential fibre Bragg grating sensor-based devices at elevated temperatures2003In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 14, no 7, p. 1131-1136Article in journal (Refereed)
    Abstract [en]

    Fibre Bragg gratings (FBGs) of type I and IIA were fabricated in Ge-doped and B-Ge co-doped fibres using a 248 nm excimer laser and their performance characteristics were tested and compared with those of a chemical composition grating (CCG), written in a fluorine-germanium doped fibre, over a wide range of temperatures. Long-term testing (more than 600 h) involving a series of step-wise incremental temperature changes shows for the first time the potential of FBGs for high temperature measurement applications (up to and beyond 1100 degreesC), this depending on the type of FBG involved and the material and composition of the substrate fibre (the CCG was observed to be the most durable at very high temperatures). These gratings are likely to be useful for the simultaneous measurement of strain and temperature over these higher temperature ranges.

  • 22.
    Pastuhoff, Markus
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Yorita, D.
    Asai, K.
    Alfredsson, P. Henrik
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Enhancing the signal-to-noise ratio of pressure sensitive paint data by singular value decomposition2013In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 24, no 7, p. 075301-Article in journal (Refereed)
    Abstract [en]

    When using pressure sensitive paint under unsteady conditions in low-speed applications, the signal-to-noise ratio is usually low and may hinder the proper evaluation of the acquired data. Here, we propose a new noise-filtering scheme that is based on singular value decomposition. As a test case, we evaluate the fluctuating pressure field due to unsteady vortex shedding on the side of a square cylinder. The proposed scheme resulted in a reduction of pixel noise of the order of two magnitudes which made it possible to obtain results regarding the spatial form of flow structures as well as the shedding frequency.

  • 23. Robert, Etienne
    Mass spectrometer calibration over wide concentration ranges in multicomponent gas mixtures2010In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 21, no 2, p. 025102-Article in journal (Refereed)
    Abstract [en]

    A quadrupole mass spectrometer (QMS) is used to measure the mixture composition of gas samples gathered in a novel burner configuration used to generate unstretched diffusion flames. The large variations of species concentration in the mixtures found in the burning chamber lead to accuracy problems due to the nonlinearities inherent to the instrument mode of operation. To obtain precise and real-time measurements, the sensitivity of the instrument is mapped to account for important changes in the sample composition. The implemented calibration procedure accounts for the concentration of the various species of interest in the burner (H-2, He, H2O, CH4, O-2, Ar, CO2) in mixtures containing up to five constituents, using up to one hundred reference mixtures. When necessary, calibration adjustments are performed using a small set of measurements to account for the effect of the drift of instrument sensitivity resulting from instrument wear or fouling. This procedure allows us to keep the relative error on the concentration of every species of interest below 5% for most of the mixtures while a classical calibration based on a limited number of reference mixtures often resulted in relative errors in excess of 50%.

  • 24.
    Robert, Etienne
    KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics.
    Mass spectrometer calibration over wide concentration ranges in multi-components gas mixtures2010In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 21, p. 025102-Article in journal (Refereed)
    Abstract [en]

    A quadrupole mass spectrometer (QMS) is used to measure the mixture composition of gas samples gathered in a novel burner configuration used to generate unstretched diffusion flames. The large variations of species concentration in the mixtures found in the burning chamber lead to accuracy problems due to the nonlinearities inherent to the instrument mode of operation. To obtain precise and real-time measurements, the sensitivity of the instrument is mapped to account for important changes in the sample composition. The implemented calibration procedure accounts for the concentration of the various species of interest in the burner (H2, He, H2O, CH4, O2, Ar, CO2) in mixtures containing up to five constituents, using up to one hundred reference mixtures. When necessary, calibration adjustments are performed using a small set of measurements to account for the effect of the drift of instrument sensitivity resulting from instrument wear or fouling. This procedure allows us to keep the relative error on the concentration of every species of interest below 5% for most of the mixtures while a classical calibration based on a limited number of reference mixtures often resulted in relative errors in excess of 50%.

  • 25. Sanchez, B.
    et al.
    Rojas, Cristian R.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Robust excitation power spectrum design for broadband impedance spectroscopy2014In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 25, no 6, p. 065501-Article in journal (Refereed)
    Abstract [en]

    This paper focuses on the robust design of broadband impedance spectroscopy (IS) experiments. This contribution extends the optimal IS experiment design presented in previous work (Sanchez et al 2012 Meas. Sci. Technol. 23 085702) in order to design a robust broadband excitation which gives relatively good estimation performance over a large number of possible impedance models. To this end, we assume as prior knowledge that the parameters of the impedance model lie in a compact set. Then, we pose the experiment design problem as a convex optimization program, which gives the excitation signal of bounded power that minimizes the worst value of a given scalar function of the Fisher information matrix, as the parameters range over the given compact set. Supported by numerical simulations, our results reveal the robust excitation for impedance experiments has a discrete power spectrum, e. g. (periodic) multisine signals.

  • 26. Sanchez, B.
    et al.
    Rojas, Cristian R.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Vandersteen, G.
    Bragos, R.
    Schoukens, J.
    On the calculation of the D-optimal multisine excitation power spectrum for broadband impedance spectroscopy measurements2012In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 23, no 8, p. 085702-Article in journal (Refereed)
    Abstract [en]

    The successful application of impedance spectroscopy in daily practice requires accurate measurements for modeling complex physiological or electrochemical phenomena in a single frequency or several frequencies at different (or simultaneous) time instants. Nowadays, two approaches are possible for frequency domain impedance spectroscopy measurements: (1) using the classical technique of frequency sweep and (2) using (non-)periodic broadband signals, i.e. multisine excitations. Both techniques share the common problem of how to design the experimental conditions, e.g. the excitation power spectrum, in order to achieve accuracy of maximum impedance model parameters from the impedance data modeling process. The original contribution of this paper is the calculation and design of the D-optimal multisine excitation power spectrum for measuring impedance systems modeled as 2R-1C equivalent electrical circuits. The extension of the results presented for more complex impedance models is also discussed. The influence of the multisine power spectrum on the accuracy of the impedance model parameters is analyzed based on the Fisher information matrix. Furthermore, the optimal measuring frequency range is given based on the properties of the covariance matrix. Finally, simulations and experimental results are provided to validate the theoretical aspects presented.

  • 27.
    Seoane, Fernando
    et al.
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Macias, Raul
    Technical University of Catalonia.
    Bragós, Ramon
    Technical University of Catalonia.
    Lindecrantz, Kaj
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Simple voltage-controlled current source for wideband electrical bioimpedance spectroscopy: circuit dependences and limitations2011In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 22, no 11Article in journal (Refereed)
    Abstract [en]

    In this work, the single Op-Amp with load-in-the-loop topology as a current source is revisited. This circuit topology was already used as a voltage-controlled current source (VCCS) in the 1960s but was left unused when the requirements for higher frequency arose among the applications of electrical bioimpedance (EBI). The aim of the authors is not only limited to show that with the currently available electronic devices it is perfectly viable to use this simple VCCS topology as a working current source for wideband spectroscopy applications of EBI, but also to identify the limitations and the role of each of the circuit components in the most important parameter of a current for wideband applications: the output impedance. The study includes the eventual presence of a stray capacitance and also an original enhancement, driving with current the VCCS. Based on the theoretical analysis and experimental measurements, an accurate model of the output impedance is provided, explaining the role of the main constitutive elements of the circuit in the source's output impedance. Using the topologies presented in this work and the proposed model, any electronic designer can easily implement a simple and efficient current source for wideband EBI spectroscopy applications, e.g. in this study, values above 150 kΩ at 1 MHz have been obtained, which to the knowledge of the authors are the largest values experimentally measured and reported for a current source in EBI at this frequency.

  • 28. Zhang, Hongxia
    et al.
    Chen, Xinwei
    Ye, Wenting
    Xu, Tianhua
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Jia, Dagong
    Zhang, Yimo
    Mitigation of the birefringence dispersion on the polarization coupling measurement in a long-distance high-birefringence fiber2012In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 23, no 2, p. 025203-Article in journal (Refereed)
    Abstract [en]

    Due to the birefringence dispersion, the polarization coupling parameter measurement in high-birefringence fiber decreases obviously with the fiber length, especially for long-distance fibers. In this paper, two methods for mitigating the birefringence dispersion in a long-distance fiber are proposed. The first method is a spectral-domain measurement method. The experimental setup and results are described in detail. The other method is a time-domain numerical dispersion compensation algorithm to amend the coupling strength calculation equation. It is based on the fact that the interferogram envelope area is constant even with the existence of birefringence dispersion. The experimental result shows that the time-domain algorithm has high accuracy, and the absolute deviation is less than 1%. The two methods are validated to mitigate the birefringence dispersion in the long-distance high-birefringence fiber effectively.

  • 29. Zhang, Hongxia
    et al.
    Xu, Tianhua
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Jia, Dagong
    Jing, Wencai
    Liu, Kun
    Zhang, Yimo
    Effects of angular misalignment in interferometric detection of distributed polarization coupling2009In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 20, no 9, p. 095112-Article in journal (Refereed)
    Abstract [en]

    White light interferometry is used to measure the distributed polarization coupling (DPC) in polarization-maintaining fibers (PMFs). By using a scanning Michelson interferometer to compensate the optical path difference (OPD) induced by the modal birefringence of PMFs, both the coupling strength and positions of the coupling points can be acquired. In ideal DPC measurement, the two reflective mirrors on the fixed and scanning arms of the Michelson interferometer are normal to each other. But in practice, the movable reflective mirror cannot be aligned normally to the fixed mirror exactly, which leads to an angular misalignment. The angular misalignment causes a variation of the OPD, which will reduce the fringe visibility. The theoretical simulation is investigated correspondingly. Consequently, the angular error leads to the miscalculation of the polarization coupling intensity. Based on the experimental results, a revised coupling strength calculation equation is proposed to minimize the influence of angular misalignment.

1 - 29 of 29
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