Reduce Measurement Time Research Articles

A Capacitance-To-Digital Converter for MEMS Sensors for Smart Applications.

The use of MEMS sensors has been increasing in recent years. To cover all the applications, many different readout circuits are needed. To reduce the cost and time to market, a generic capacitance-to-digital converter (CDC) seems to be the logical next step. This work presents a configurable CDC designed for capacitive MEMS sensors. The sensor is built with a bridge of MEMS, where some of them function with pressure. Then, the capacitive to digital conversion is realized using two steps. First, a switched-capacitor (SC) preamplifier is used to make the capacitive to voltage (C-V) conversion. Second, a self-oscillated noise-shaping integrating dual-slope (DS) converter is used to digitize this magnitude. The proposed converter uses time instead of amplitude resolution to generate a multibit digital output stream. In addition it performs noise shaping of the quantization error to reduce measurement time. This article shows the effectiveness of this method by measurements performed on a prototype, designed and fabricated using standard 0.13 µm CMOS technology. Experimental measurements show that the CDC achieves a resolution of 17 bits, with an effective area of 0.317 mm2, which means a pressure resolution of 1 Pa, while consuming 146 µA from a 1.5 V power supply.

Determination of inter-ionic and intra-ionic interactions in a monofluorinated imidazolium ionic liquid by a combination of X-ray crystallography and NOE NMR spectroscopy.

We report the very first application of a Transient 1D 1 H{19 F} NOE NMR experiment in neat ionic liquids. In comparison with classical 2D HOESY NMR spectroscopy, a substantial reduction in measurement time is gained with comparable quality and information content of the spectra. In combination with classical X-ray crystallography, we have applied this technique for the determination of inter-ionic distances (i.e. probabilities of presence) utilizing an ionic liquid containing a monofluorinated imidazolium cation. Copyright © 2017 John Wiley & Sons, Ltd.

Calibration and data extraction in nonoptimized Mueller matrix polarimeters.

We present a method for calibration and data extraction for a nonoptimized Mueller matrix polarimeter. The advantage of this type of method is a reduction in measurement time for multiwavelength systems or in systems with slow response times. The calibration process requires the measurement of four known polarization devices. Here we use free-space transmission, a horizontal and a vertical linear polarizer, and a quarter-wave retarder with its fast axis at 30° to the horizontal. Experimental measurements of rotating quarter-wave and half-wave retarders show that accurate results can be obtained with the proposed method.

Large-field-of-view optical elastography using digital image correlation for biological soft tissue investigation.

.In minimally invasive surgery the haptic feedback, which represents an important tool for the localization of abnormalities, is no longer available. Elastography is an imaging technique that results in quantitative elastic parameters. It can hence be used to replace the lost sense of touch, as to enable tissue localization and discrimination. Digital image correlation is the chosen elastographic imaging technique. The implementation discussed here is clinically sound, based on a spectrally engineered illumination source that enables imaging of biological surface markers (blood vessels) with high contrast. Mechanical loading and deformation of the sample is performed using a rolling indenter, which enables the investigation of large organs (size of kidney) with reduced measurement time compared to a scanning approach. Furthermore, the rolling indentation results in strain contrast improvement and an increase in detection accuracy. The successful application of digital image correlation is first demonstrated on a silicone phantom and later on biological samples. Elasticity parameters and their corresponding four-dimensional distribution are generated via solving the inverse problem (only two-dimensional displacement field and strain map experimentally available) using a well-matched hyperelastic finite element model.

Analysis and Estimation of MIMO-SAR for Multi-antenna Mobile Handsets

Measuring multiple-input multiple-output (MIMO) specific absorption rate (SAR) is an important part of mobile handset evaluation, following the introduction of uplink MIMO transmission schemes in long-term evolution advanced systems. However, the measurement of MIMO-SAR is complex and time consuming. In this communication, six unique dual-antenna mobile handsets, including both typical and novel designs, are analyzed to determine the dependence of MIMO-SAR on antenna configuration and correlation. It is found that, for certain antenna configurations, the location of the maximum MIMO-SAR and the corresponding relative phase between the ports can be predicted. This can be applied to drastically reduce measurement time. In addition, dual antennas with low envelope correlation coefficients in the radiation patterns also offer near-orthogonal electric near fields. This leads to smaller MIMO-SAR than stand-alone SAR (S-SAR) over all relative phases, making MIMO-SAR measurement unnecessary. The results also provide guidelines for designing multi-antenna handsets with low SARs. For verification, the S-SAR and MIMO-SAR at a relative phase of 0° were measured for several prototypes. The measured SAR distributions showed good agreement with the simulated ones.

Compressed Sensing Current Mapping Spatial Characterization of Photovoltaic Devices

A new photovoltaic (PV) device current mapping method has been developed, combining the recently introduced compressed sensing (CS) sampling theory with light beam induced current (LBIC) measurements. Instead of a raster scan, compressive sampling is applied using a digital micromirror device. The aim is to significantly reduce the time required to produce a current map, compared to conventional LBIC measurements. This is achieved by acquiring fewer measurements than a full raster scan and by utilizing the fast response of the micromirror device to modulate measurement conditions. The method has been implemented on an optical current mapping setup built at the National Physical Laboratory, U.K. Measurements with two different PV cells are presented in this paper and an analytical description for realization of an optimized CS current mapping system is provided. The experimental results illustrate the feasibility of the method and its potential to significantly reduce measurement time of current mapping of PV devices.

Ring Laser Gyro-based Digital Processing Technique for Detecting Rotation Rate over Short Time Intervals

The article investigates capabilities of digital techniques to improve measurement accuracy of dithering ring laser gyro (DRLG) in detecting constant rotation rate over short time intervals. An array of the GL-1 device output within a LG triad to measure the vertical component of the angular rate of rotation of the Earth in the laboratory setting is selected as the object of study. The selected time of a single measurement is 2 minutes, and as a full standard deviation error of measurement is selected the magnitude at least 0.002 / min. The objective of this study is to develop and underpin a new effective technique of LG digital information processing to enable providing an appropriate accuracy to meet modern requirements with reducing measurement time of a constant rate Ωz component. The specific objectives are the comparative analysis of the precision capabilities of the known techniques over limited measurement time intervals, development and support of new, more efficient technique of digital information processing of dithering ring LG, and experimental verification and evaluation of effectiveness of the technique proposed. The article presents a comparative error analysis of practically applied digital techniques such a simple averaging method, Hamming method, and method of conditional sample of regression lines with the proposed technique of of the output signal of the image N. To compare the techniques were used the real digital processing device output data taken at a frequency of 400 Hz over 94 two-minute measurement intervals after the device has been switched on. The proposed LG output image recognition technique enables us to reach about three times higher measuring accuracy over two-minute interval as compared to the known techniques.

Sensor fusion of electron paramagnetic resonance and magnetorelaxometry data for quantitative magnetic nanoparticle imaging

Magnetorelaxometry (MRX) imaging and electron paramagnetic resonance (EPR) are two non-invasive techniques capable of recovering the magnetic nanoparticle (MNP) distribution. Both techniques solve an ill-posed inverse problem in order to find the spatial MNP distribution. A lot of research has been done on increasing the stability of these inverse problems with the main objective to improve the quality of MNP imaging. In this paper a proof of concept is presented in which the sensor data of both techniques is fused into EPR–MRX, with the intention to stabilize the inverse problem. First, both techniques are compared by reconstructing several phantoms with different sizes for various noise levels and calculating stability, sensitivity and reconstruction quality parameters for these cases. This study reveals that both techniques are sensitive to different information from the MNP distributions and generate complementary measurement data. As such, their merging might stabilize the inverse problem. In a next step we investigated how both techniques need to be combined to reduce their respective drawbacks, such as a high number of required measurements and reduced stability, and to improve MNP reconstructions. We were able to stabilize both techniques, increase reconstruction quality by an average of 5% and reduce measurement times by 88%. These improvements could make EPR–MRX a valuable and accurate technique in a clinical environment.

Automated Measurement of Magnesium/Calcium Ratios in Gastropod Shells Using Laser-Induced Breakdown Spectroscopy for Paleoclimatic Applications

The chemical composition of mollusk shells offers information about environmental conditions present during the lifespan of the organism. Shells found in geological deposits and in many archeological sites can help to reconstruct past climatic conditions. For example, a correlation has been found between seawater temperature and the amount of some substituent elements (e.g., magnesium, strontium) in the biogenerated calcium carbonate matrix of the shell, although it is very species-specific. Here we propose the use laser-induced breakdown spectroscopy (LIBS) to estimate Mg/Ca ratios in modern specimens of the common limpet Patella vulgata. An automated setup was used to obtain a sequence of Mg/Ca ratios across a sampling path that could be compared with the seawater temperatures recorded during the organism's lifespan. Results using four shells collected in different months of the year showed a direct relationship between the Mg/Ca ratios and the seawater temperature, although the sequences also revealed small-scale (short-term) variability and an irregular growth rate. Nevertheless, it was possible to infer the season of capture and the minimum and maximum seawater temperatures from the LIBS sequences. This fact, along with the reduction in sampling and measurement time compared with other spectrometric techniques (such as inductively coupled plasma mass spectrometry [ICP-MS]), makes LIBS useful in paleoclimatic studies.

Time-Domain Methodology for the Relatively Low-Frequency Characterization of Large Antennas

Frequency-domain measurement techniques in an enclosed area suffer from some limitations when dealing with antennas of large physical dimensions or when operating in the low-frequency range. This paper presents a measurement test bench for antenna characterization based on outdoor time-domain measurements. The setup is applied to ultra-wide-band and narrow-band antennas yielding good far-field antenna characterization results as compared to standard measurement techniques. This approach employs a near-field to far-field transformation technique to obtain the radiation pattern of any radiating structure over a wide band of frequencies, from a single time-domain near-field data acquisition. The suggested approach offers significant savings in installation and material cost, in addition to a considerable reduction in measurement time.

Validation of a Rapid Colorimetric Method with Field Soils

Abstract. Regularly monitoring the variations in soil composition is an essential part of proper cultivation management. Some conventional soil characterization methods are often costly and require experienced labor. The spectroscopic method is a simpler procedure that minimizes experimental steps and is faster and more economical than conventional methods. Wide-ranging analytical methods have been developed to determine soil phosphorus concentrations in the field; however, no method has been commercialized. Analytical methods based on colorimetric Mehlich-3 and Lancaster soil tests, developed to reduce measurement time in laboratories in the U.S. and South Korea, have been efficient. However, due to laboratory procedures, the soil was pretreated and not verified with field soil. We tested the rapid colorimetric method, which is for on-site plant-available soil phosphorus tests in the field and allows reduced analysis time. The target accuracy of the field tests was >70% correlation with laboratory test results. This method consists of three steps: fast extraction, fast filtration, and fast color development. In a comparison of the rapid colorimetric method and the standard laboratory procedure, the R2 values were 0.78, 0.71, 0.72, and 0.74, respectively, for field soils collected in four regions of South Korea. However, the results showed significant differences in some areas. When the moisture content and electrical conductivity of soil from each region were included in the multiple regression analysis, the cross-validation results showed superior output with no significant difference (p > 0.05). Keywords: Colorimetry, Phosphorus, Precision agriculture, Sensor, Soil.

Hong-Ou-Mandel interference between two independent all-fiber multiplexed photon sources

Interference between independent photon sources is the key technique to realize complex quantum systems for more sophisticated applications such as multi-photon entanglement generation and quantum teleportation. Here, we report Hong-Ou-Mandel interference (HOMI) between two independent 1.55 m all-fiber photon pair sources over two 100 GHz dense wave division multiplexing (DWDM) channels, whose visibility reaches 53.2%8.4% (82.9%5.3%) without (with) back ground counts subtracted. In addition, we theoretically describe in detail the single photon spectral purity of the photon source generated in dispersion shifted fiber (DSF), simulate the influences of the pulse width and filter bandwidth on the purity, and obtain the optimized condition. The optimized pump pulse width is 8 ps and filter bandwidth is about 40 GHz or less. A home-made 1550.1 nm mode-locked fiber laser source, whose pulse width and repetition rate are 25 ps and 27.9 MHz respectively, acts as a pump of photon source. A tunable attenuator is used to adjust the pump power of the photon source, and the broad band background fluorescence photons are filtered out by cascade 100 GHz DWDM filters. The clean pump beam is divided into two equal parts by the 50 : 50 optical coupler to pump two 300 m DSFs (cooled by liquid nitrogen) to generate independent photon sources. Then the strong pump beam and noise photon from Raman scattering in orthogonal polarization are removed by 2 groups of 200 GHz DWDM filters and fiber polarization rotator and polarizer. Then two 100 GHz DWDMs are used for separating photons at correlated channel pairs. The relative delay between the two independent photons is adjusted by tunable fiber delay line. Photons from the same channels are combined in a second beam splitter for interference, and the other two photons are used as trigger signals. The two triggered photons are detected by two free running InGaAs avalanched single photon detectors (APD1, APD4, ID Quanta, ID220, 20% detection efficiency, 3 s dead time, dark count rate 4k cps), and the outputs of detectors APD1 and APD4 are used to trigger two single-photon detectors running in the gated mode (APD2, APD3, Qasky, Hefei, China, 100 MHz, free gating single photon detectors, 20% detection efficiency, dark count probability 410-5 per gate) for twophoton coincidence measurement. Detection output signals from APD2 and APD3 are sent to our coincidence count device (Pico quanta, TimeHarp 260, 1.6 ns coincidence window) for four-photon coincidence measurement. Before measuring the HOMI, we obtain a maximum-coincidence-to-accidental-coincidence ratio (CAR) of 131 by cooling the fiber in liquid nitrogen when the pump power is 23 W. There are a few remarks we want to point out.Firstly, the photon sources are not operated at the optimized pump pulse width for pure single photon generation, but narrow band 100 GHz filters are used in the experiments to increase the purity of the sources. Secondly, single photon detectors used in our experiment have lower detection efficiency and much higher dark counts than nano-wire single photon detectors, if we have high-performance nano-wire single photon detector, experimental results will be greatly improved due to the four-fold coincidences and dark coincidences scaling quadruplicate with the detection efficiency and dark count probability of a single detector. Thirdly, we use relatively high pump power for each DSF (0.12 mW) to reduce measurement time for photon coincidence, which will lead to a very poor raw visibility certainly. Finally, though only a 100 GHz channel pair is used in our experiment, we can use other channels for multiplexing such interference processes to improve the channel capacity in future quantum communication tasks theoretically. Our study shows greatly promising integrated optical elements for future scalable quantum information processing.

Present and future experiments using bright low-energy positron beams

Bright slow positron beams enable not only experiments with drastically reduced measurement time and improved signal-to-noise ratio but also the realization of novel experimental techniques. In solid state physics and materials science positron beams are usually applied for the depth dependent analysis of vacancy-like defects and their chemical surrounding using positron lifetime and (coincident) Doppler broadening spectroscopy. For surface studies, annihilation induced Auger-electron spectroscopy allows the analysis of the elemental composition in the topmost atomic layer, and the atomic positions at the surface can be determined by positron diffraction with outstanding accuracy. In fundamental research low-energy positron beams are used for the production of e.g. cold positronium or positronium negative ions. All the aforementioned experiments benefit from the high intensity of present positron beam facilities. In this paper, we scrutinize the technical constraints limiting the achievable positron intensity and the available kinetic energy at the sample position. Current efforts and future developments towards the generation of high intensity spin-polarized slow positron beams paving the way for new positron experiments are discussed.

Validation of the Decomposition Method for Fast MIMO Over-the-Air Measurements

Over-the-air (OTA) throughput tests of wireless Multiple-Input Multiple-Output (MIMO) devices are an important tool for network operators and manufacturers. The user equipment (UE) is placed in an anechoic chamber and a random fading process is emulated by a base-station emulator (BSE). The antenna characteristic of the UE is taken into account by sampling the sphere around the UE with the BSE test antenna at a large number of positions. For low-variance throughput results, long measurement intervals over many fading realizations are required, leading to long and expensive measurement periods in an anechoic chamber. To speed up the OTA test, we analyze the Decomposition Method (DM). The DM splits the throughput measurement into two parts: (1) a receiver algorithm performance tests taking the fading process into account and (2) an antenna performance test without fading process emulation. Both results are combined into a single throughput estimate. The DM allows for a measurement time reduction of more than one order of magnitude. We provide an analytic and numerical analysis as well as measurements. Our detailed results show the validity of the DM in all practical settings.

The clinical relevance of distortion correction in presurgical fMRI at 7 T

Presurgical planning with fMRI benefits from increased reliability and the possibility to reduce measurement time introduced by using ultra-high field. Echo-planar imaging suffers, however, from geometric distortions which scale with field strength and potentially give rise to clinically significant displacement of functional activation.We evaluate the effectiveness of a dynamic distortion correction (DDC) method based on unmodified single-echo EPI in the context of simulated presurgical planning fMRI at 7T and compare it with static distortion correction (SDC). The extent of distortion in EPI and activation shifts are investigated in a group of eleven patients with a range of neuropathologies who performed a motor task. The consequences of neglecting to correct images for susceptibility-induced distortions are assessed in a clinical context.It was possible to generate time series of EPI-based field maps which were free of artifacts in the eloquent brain areas relevant to presurgical fMRI, despite the presence of signal dropouts caused by pathologies and post-operative sites. Distortions of up to 5.1mm were observed in the primary motor cortex in raw EPI. These were accurately corrected with DDC and slightly less accurately with SDC. The dynamic nature of distortions in UHF clinical fMRI was demonstrated via investigation of temporal variation in voxel shift maps, confirming the potential inadequacy of SDC based on a single reference field map, particularly in the vicinity of pathologies or in the presence of motion. In two patients, the distortion correction was potentially clinically significant in that it might have affected the localization or interpretation of activation and could thereby have influenced the treatment plan.Distortion correction is shown to be effective and clinically relevant in presurgical planning at 7T.

On the Dynamic Measurements of Hydraulic Characteristics

The present work introduces the implementation and validation of a faster method to measure experimentally the efficiency characteristics of hydraulic turbomachines at a model scale on a test rig. The case study is represented by a laboratory prototype of an in-line axial microturbine for water supply networks. The 2.65 kW one-stage variable speed turbine, composed by one upstream 5-blade runner followed by one counter-rotating downstream 7-blade runner, has been installed on the HES-SO Valais/Wallis universal test rig dedicated to assess performances of small hydraulic machinery following the IEC standard recommendations.In addition to the existing acquisition/control system of the test rig used to measure the 3D hill-chart of a turbine by classical static point-by-point method, a second digitizer has been added to acquire synchronized dynamic signals of the employed sensors. The optimal acceleration/deceleration ramps of the electrical drives have been previously identified in order to cope with the purpose of a reduced measurement time while avoiding errors and hysteresis on the acquired hydraulic characteristics. Finally, the comparison between the turbine efficiency hill-charts obtained by dynamic and static point-by-point methods shows a very good agreement in terms of precision and repeatability. Moreover, the applied dynamic method reduces significantly (by a factor of up to ten) the time necessary to measure the efficiency characteristics on model testing.

Estimation of steady-state leakage current in polycrystalline PZT thin films

Estimation of the steady state (or “true”) leakage current Js in polycrystalline ferroelectric PZT films with the use of the voltage-step technique is discussed. Curie-von Schweidler (CvS) and sum of exponents (Σexp) models are studied for current-time J (t) data fitting. Σexp model (sum of three or two exponents) gives better fitting characteristics and provides good accuracy of Js estimation at reduced measurement time thus making possible to avoid film degradation, whereas CvS model is very sensitive to both start and finish time points and give in many cases incorrect results. The results give rise to suggest an existence of low-frequency relaxation processes in PZT films with characteristic duration of tens and hundreds of seconds.

Novel 3D measurement system based on speckle and fringe pattern projection.

An efficient three-dimensional shape measurement system is proposed, which is based on the combining projection of single digital speckle pattern and phase-shifting fringe patterns. At the beginning, the initial corresponding point for each pixel is obtained by a novel speckle-phase combination method. The initial information can be calculated by the single speckle pattern in a short time, while the phase information is used to ensure the results. Unlike the conventional methods, it is not necessary to obtain the unwrapped phase, therefore the number of projected patterns is reduced greatly. Then accurate corresponding coordinates are obtained according to the wrapped phase. Three cases are analyzed while adjusting the initial corresponding coordinates locally. Thus accuracy coordinates are obtained without missing or incorrect points. Experiments demonstrate that we can achieve accurate reconstruction results with reduced measurement time by the proposed method.

An advanced viscosity and density sensor based on diamagnetically stabilized levitation

We present a viscosity and density measurement principle based on diamagnetically stabilized levitation of a test object (a floating magnet) in the fluid to be characterized. Miniaturized resonant viscosity sensors are usually operated at relatively high frequencies, ranging from the lower kHz to tens of MHz, which utilize shear waves penetrating the liquid in the close vicinity of the vibrating surface thus only enabling the sensing of a small liquid film on the surface. With our approach, we reduce the resonance frequency which increases the penetration depth of the shear wave. Due to the freely levitated measurement body and the magnetic readout no mechanical or electrical connections into the measurement chamber are necessary, making the setup particularly useful for sterile, toxic or poisonous fluids. The design of the setup allows different modes of operation for the floater magnet, e.g., linear oscillations along the (vertical) z-axis and rotational oscillations around the (horizontal) x- or y-axis. In this contribution we analyze the rotational oscillation mode and present a theoretical model. Different additional features such as frequency tunability or the influence of the levitation height are examined. Measurements are discussed that prove the theoretical model and demonstrate the functionality of the principle. The use of rotatory oscillations instead of linear movements leads to a reduced measurement time and less influence of the boundaries.

Tissue diagnosis using power-sharing multifocal Raman micro-spectroscopy and auto-fluorescence imaging.

We describe a multifocal Raman micro-spectroscopy detection method based on a digital micromirror device, which allows for simultaneous “power-sharing” acquisition of Raman spectra from ad hoc sampling points. As the locations of the points can be rapidly updated in real-time via software control of a liquid-crystal spatial light modulator (LC-SLM), this technique is compatible with automated adaptive- and selective-sampling Raman spectroscopy techniques, the latter of which has previously been demonstrated for fast diagnosis of skin cancer tissue resections. We describe the performance of this instrument and show examples of multiplexed measurements on a range of test samples. Following this, we show the feasibility of reducing measurement time for power-shared multifocal Raman measurements combined with confocal auto-fluorescence imaging to provide guided diagnosis of tumours in human skin samples.