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The availability of reliable analytical models is essential to the optimal design of energy harvesters and for the prediction of the system behavior. In this paper, we consider a low-input nonlinear system based on a flexible buckled beam forced in a bistable configuration. The harvester has been demonstrated to generate power in the excess of $400~\mu \text{W}$ with the optimal resistive load of 15 $\text{k}\Omega $ and a monotonic input with root-mean-square accelerations of 13.35 m/s2. The power generated is suitable for powering low-power measurement systems or sensor nodes. This paper focuses on a methodology for the modeling of the mechanical dynamical behavior of the device subject to a periodic impulsive signal. A measurement protocol for the evaluation of system’s hidden quantities, the beam’s restoring force, and the beam’s displacement between its stable states is introduced. A second-order behavioral model with a nonlinear term representing the beam’s restoring force has been used. In order to model the nonlinearity, two different potential energy functions have been compared by fitting the models to the experimental data with different constrains, through a performance index evaluating the fitting error. [ABSTRACT FROM AUTHOR]

This paper investigates the performance of switch-mode power supplies used in desktop PCs (PC-SMPS’) across the entire range of operating powers. Experimental results show that at low to medium operating powers, the input ac current might lose its periodicity with supply voltage frequency, when PCS-MPS’ can be an unexpected source of interharmonics and dc component. In such cases, there is a significant increase of PC-SMPS’ current waveform distortion and a substantial decrease of efficiency and operational power factors, which requires application of appropriate measurement and calculation procedures during the analysis. To correctly assess these power-dependent changes in performance and power quality indicators, this paper introduces a novel testing and evaluation methodology, based on the known or assumed PC-SMPS operating cycle. [ABSTRACT FROM AUTHOR]

This paper describes the application of a pulse pileup correction algorithm based on maximum likelihood estimation to simulated and experimentally acquired signals from a pyroelectric ultrasound sensor. The sensor forms part of a prototype phase-insensitive ultrasound computed tomography (piUCT) system for breast cancer detection that generates quantitative maps of acoustic attenuation. The effectiveness of the piUCT technique has been previously demonstrated through imaging of cylindrical, polyurethane phantoms. For the technique to be applied clinically, the system must be capable of measuring high acoustic attenuations (>30 dB) and completing a scan in a clinically acceptable time frame of approximately 5 min. High attenuations present a challenge because the sensor responds directly to acoustic power and therefore, an attenuation of 30 dB causes a drop in signal level of three orders of magnitude, resulting in a large dynamic range in the received signal set. Completion of a scan in 5 min requires a period between measurements shorter than the response time of the sensor, causing pyroelectric pulse pileup. The maximum likelihood estimation method recovers the amplitudes of closely spaced superimposed pyroelectric signals while improving the coefficient of variation of the measurement by a factor of two compared to direct pulse amplitude measurement, simultaneously increasing the maximum measurable attenuation and measurement rate of the system. [ABSTRACT FROM AUTHOR]

An on-load tap changer (OLTC) is one of the most error-prone parts in the transformer. The stability of the entire power system will be greatly threatened if the OLTC fails. It is necessary to diagnose the mechanical fault of OLTCs. At the same time, the mechanical fault signals are not easy to collect during practical application. It is desirable to have indicators that help to access the condition of the OLTC with a small number of fault samples. This paper describes a strategy for distinguishing different mechanical diagnostics of OLTCs based on dynamic time warping. By synchronization, framing, and Fourier transform, the signal can be represented by an energy matrix, which can be used to distinguish different conditions of the OLTCs and shows the severities of the fault. Some simulated experiments are designed and in order to make the simulations close to reality, all experiments are taken in a tank which is filled with transformer oil. These experiments demonstrate that the proposed approach can effectively diagnose different OLTC faults under different fault severities. [ABSTRACT FROM AUTHOR]

In this paper, a measurement methodology for the characterization of the mechanical and electrical behavior of a nonlinear vibrational harvester is discussed and demonstrated on a real case study. The harvester, here considered, takes advantage of a flexible beam in a snap-through-buckling configuration and a novel magnetic repulsion mechanism to compensate for the asymmetric behavior of the device, in the vertical direction, due to the effect of the proof mass load. A measurement protocol aimed at the device performance estimation in terms of the minimum acceleration, the number of switching events, the output voltage, the generated power, and the mechanical-to-electrical conversion efficiency of the system is discussed. The advantages of the proposed compensation strategy are highlighted by evaluating the device’s performances in the range of frequency 0.5–12 Hz for different tilts applied to the device and compared to the performance of the same device without the repulsion mechanism. The harvester is capable of scavenging energy in the range 0.5–5 Hz with acceptable efficiency; it can, however, be exploited up to 12 Hz with an acceptable loss of efficiency. A power of about $412~\mu \text{W}$ with a root-mean-square acceleration of 10.22 m/s2 at 5 Hz and an efficiency of about 23.5% has been measured for the harvester, with the repulsive mechanism, operated in the vertical position. The power generated is suitable for powering wireless devices. [ABSTRACT FROM AUTHOR]

The use of nonlinear architectures for energy harvesting can significantly improve the efficiency of the conversion mechanism, as respect to the use of linear devices, especially when the mechanical energy is distributed over a wide frequency bandwidth. This is the case of energy harvesting form wideband vibrations. In this paper, performances of a piezoelectric energy harvester exploiting a snap-through buckling configuration are investigated. The device is supposed to switch between its stable states, where two piezoelectric transducers are positioned to implement the mechanical-to-electric conversion mechanism. A simple theoretical two-state model of the device is presented along with a complete experimental characterization aimed at investigating the mechanical and electrical behaviors of the device. The device is demonstrated to be capable of scavenging energy from vibration sources in the range 0.5–5 Hz, but could be exploited up to 15 Hz with an acceptable loss of efficiency. The bandwidth of the device is compatible with applications where the vibrations occur at low frequencies, e.g., in the case of a running human. In this paper, we demonstrate the viability of our setup for harvesting energy from mechanical vibrations. The device is seen to generate power up to 155~\mu \textW at 5 Hz; the power is sufficient to operate a standard wireless sensor node. The conversion efficiency of the harvester in the range 0.5–5 Hz is from 13% up to 18% with an average of 15%. [ABSTRACT FROM PUBLISHER]

This paper presents a comprehensive investigation of several important error sources for the successive-approximation register (SAR) analog-to-digital converters (ADCs). The error sources that we discuss in this paper include the dynamic comparator offset, the dynamic gain error of digital-to-analog converter (DAC), the capacitor mismatch of capacitive DAC, the incomplete settling of DAC, the undershoot of reference voltage, and the input signal coupling. The integral/differential nonlinearities (INL/DNL) of SAR ADCs that are resulted from these error sources are analyzed and addressed. A diagnostic procedure is presented to identify the possible error sources based on the INL/DNL plots. In addition, design suggestions for overcoming these problems are also offered and recommended in this paper. [ABSTRACT FROM AUTHOR]

This paper describes a new phase difference measurement system based on the three-voltmeter method (3VM) by introducing differential ac/single-ended dc switching for a thermal voltage converter (TVC). The 3VM-based phase difference measurement system has been developed in consideration of the simulation results and the loading effects derived from the TVC. The expanded uncertainties of differential voltage and phase difference measurements have been estimated (e.g., $80~\mu \text{V}$ and 0.0073° at 10 V/1 V, 1 kHz, and 60°). The phase difference measurement uncertainties of two voltage conditions ($V_{1} > V_{2}$ and $V_{1} = V_{2}$) have been focused and theoretically formulated. The phase difference measurements by the system have been made in the voltage range of 1 to 10 V at 1 kHz and 60°. The measurement results agree well with those obtained by a phase standard. [ABSTRACT FROM AUTHOR]

This paper presents a simple, novel interfacing scheme for linear variable differential transformer (LVDT) that does not require a precise sine wave oscillator (with stable amplitude and frequency) for excitation or any phase matching circuit like traditional methods. The primary and the secondary coils of the LVDT are integral parts of a relaxation oscillator (RO). The RO injects a current waveform with a triangular shape through the primary coil which in turn induces a square-shaped voltage waveform in the secondary coils. The RO utilizes the amplitudes of those waveforms and generates a pulsewidth modulation (PWM) output signal whose duty cycle ratio is proportional to the measurand, core position. This quasi-digital PWM signal is passed through a low-pass filter to obtain an analog output. PWM time period measurement using a counter yields a digital output. This method guarantees good stability since the output is dependent only on a pair of dc reference voltages apart from the transformation constant of the sensor. A detailed analysis of the sources of error, their effect on the performance of the scheme and appropriate design choices for error mitigation are also presented. A prototype of the proposed circuit was built and tested in the laboratory. The nonlinearity error noted from the tests conducted was less than 0.16% for the analog output and 0.18% for the digital output. A resolution of up to 11 bits was achieved for the digital output. [ABSTRACT FROM AUTHOR]

This paper introduces an oversampling, noise-shaping differential successive-approximation-register capacitance-to-digital converter (CDC) architecture for interfacing capacitive sensors. The proposed energy-efficient CDC achieves high-precision capacitive resolution by employing oversampling and noise shaping. The switched-capacitor (SC) integrator is inserted between the comparator and the charge-redistribution digital-to-analog converter to implement noise shaping and to make the interface circuit insensitive to parasitic capacitances. An inverter-based operational transconductance amplifier with a common-mode feedback circuit is employed to implement the SC integrator with subthreshold biasing for low voltage and low power. The ring-oscillator-based comparator is implemented to achieve high energy efficiency. The test chip is fabricated in a 0.18- $\mu \text{m}$ CMOS technology. The proposed CDC experimentally achieves 150 aF absolute resolution and 12.74-ENOB with an oversampling ratio of 15 and a sampling clock of 18.51 kHz. The fabricated prototype dissipates 1.2 and 0.39 $\mu \text{W}$ from analog and digital supplies, respectively, with an energy efficiency figure-of-merit of 187 fJ/conversion step. [ABSTRACT FROM AUTHOR]

In this paper, the results of the investigations on a system for energy harvesting from wideband vibrations are presented. The harvester adopts a nonlinear snap-through buckling configuration and two piezoelectric transducers, placed near the inflection points of the potential energy function that underpins the dynamics of the system. The device is capable of scavenging energy from vibration sources in the range of 0.5–7 Hz, but could be exploited up to 10 Hz with an acceptable loss of efficiency. The bandwidth of the device is compatible with applications where the vibrations occur at low frequencies, e.g., in the case of a running human. Powers of about $416~\mu \text{W}$ with root-mean-square accelerations of 13.35 m/s2 at 7 Hz and an efficiency of about 24.6% have been measured in case of a sinusoidal vibration while powers of about $250~\mu \text{W}$ and an efficiency of about 15.7%, have been measured in case of a noise input limited at 15 Hz, with a standard deviation of the accelerations of about 15.1 m/s2. The performance of the harvester is compared with a different configuration where the piezoelectric transducers are placed at the two minima of the (bistable) potential energy function that underpins the dynamics; the minima correspond to the stable states of the beam. [ABSTRACT FROM AUTHOR]

Power usage reduction and efficiency enhancement of measurement devices are a major challenge in self-powered wireless sensor nodes and also sensors implanted in the human body. Such instruments should be usually operated using the limited environmental energy resources. Electrochemical sensors and potentiostats are extensively used in this context for the measurement of chemical components. In these cases, a lot of research has focused on internal processing blocks power reduction of the potentiostat circuit. In this paper, a discrete current mode (DCM) switching potentiostat is presented, which can significantly reduce the static power usage at the output stage of the potentiostat compared with linear output stage counterparts. Using time-domain analyses, the unexpected oscillatory behavior of a continuous current mode (CCM) output stage switching potentiostat is investigated. Consecutively, it is shown that in current fabrication processes, this configuration will consume more power than the DCM topology. The correctness of the designs and analyses are shown using both simulation and experimental results. The simulated 0.18- $\mu \text{m}$ CMOS DCM output stage potentiostat has an efficiency of 95% at an output load of $12~\mu \text{A}$ , while the long-channel MOSFET-based prototype implementation shows an efficiency of 64%. [ABSTRACT FROM AUTHOR]

This paper deals with a low-cost diagnostic technique for polymer electrolyte membrane (PEM) fuel cells (FCs), which exploits the ripple produced by power converters to monitor the equivalent ohmic resistance. While the available literature on this topic is focused on constant-frequency control of the power converter (such as pulsewidth modulation), this paper discusses the measurement issues that arise when hysteresis current control is employed for a dc/dc boost converter, which represents the simplest solution from the implementation point of view, and therefore particularly suitable for low-cost applications. The classic frequency-domain analysis for ohmic resistance identification, based on the Fourier transform, is compared with a time-domain analysis based on a simple identification algorithm, and a real-time implementation of the latter is presented. The experimental results are obtained on a single PEM FC, but the extension to FC stacks for commercial applications is also discussed. [ABSTRACT FROM PUBLISHER]

The gallium nitride transistors suffer from current collapse effect in operation regions, which leads the dynamic ON-resistance to increase when high voltage is applied to the transistor. Dynamic ON-resistance under practical application conditions is also an important factor for the reliability and conduction efficiency of transistors. To measure the dynamic ON-resistance and evaluate the current collapse effect, a softswitching circuit based on synchronous buck topology is proposed in this paper. To apply high-voltage and high-current stresses to the device without additional spikes and oscillation, resonance technique has been employed. As a result, the proposed circuit could produce sufficient power stresses to the devices with general equipment. To achieve accurate measurement of ON-resistance under switching operations and eliminate the saturation of oscilloscope probes, an active voltage clamp circuit is developed. Operation principles and design analysis of the circuit are described in this paper. The dynamic ON-resistance measurement method is illustrated in detail. Furthermore, a prototype circuit has been built. A simulation and experiments were carried out to verify the performance of the system. A comparison of the active clamp circuit with common voltage probes is presented through the measurement results. The experimental results confirm that dynamic ON-resistance can be accurately measured using the proposed circuit and the current collapse effect can be evaluated under practical operation conditions with high precision. [ABSTRACT FROM PUBLISHER]

This paper introduces a new data-driven bottom-up monitoring approach for distribution systems. In this approach, local estimations of the subsections into which the system is split are performed independently, thus leading to a scalable architecture. The monitoring approach is focused only on the estimation of voltage magnitude rather than the complete state of the system. This reduces the measurement requirements significantly, thus addressing economical and technical concerns for existing systems, while staying open to accommodating further incremental improvements in the available data and data quality. The estimation of each section is realized via an artificial neural network (ANN), for which a set of parameterizations is available to cope with different operating conditions. The estimation convergence is achieved even with relatively few measurements, although accuracy varies depending on the available measurements. At the Medium Voltage (MV) level, where reconfiguration is common, a configuration identification unit chooses the right ANN, the one trained for the actual network configuration. The estimation process is computationally simple and can be executed on low-cost hardware, as demonstrated in this paper by the implementation on a BeagleBone Black board. To demonstrate the concept, a prototype and a laboratory setup have been developed. The experimental test results are presented both for an Low Voltage distribution system and an MV distribution system. [ABSTRACT FROM PUBLISHER]

Accurate estimation of the rotor position is essential for reliable start-up and sensorless control of switched reluctance motor drives. In this paper, a series of position estimation schemes based on phase inductance vector coordinate transformations are proposed. Using the rotating coordinate transformation and coordinate components normalization, the dc component and higher order harmonics of the normalized three-phase coordinate components can be eliminated effectively. According to the coordinate transformation theory, the rotating speed of the space vector is synchronized with the angular frequency of the three-phase inductance. Thus, through alpha–beta transformation, the synchronous rotating angle of the space vector and the rotor position can be estimated. Since the rotating angle can be arbitrary, it is possible to construct another coordinate system and find one of its normalized coordinate components that is perpendicular to the one in the former coordinate system. Based on the orthogonal coordinate transformation, the rotor position can also be estimated. Experiments have been implemented for verification. The proposed methods effectively solve the challenges in initial rotor position estimation and are also suitable for reliable sensorless starting under light-load conditions. However, these methods are not suitable for high-load driving–running conditions. To solve this problem, a combination of the phase current slope difference comparison-based method and the coordinate transformation-based method is developed in this paper. The experimental results verified the validity of this method. In addition, the proposed methods do not require additional hardware and complex computation, which simplifies the implementation. [ABSTRACT FROM PUBLISHER]

In this paper, a practical fault diagnosis algorithm is presented to realize multiple open-circuit fault diagnosis for photovoltaic (PV) inverters. By the feature analysis for the output currents of normal and fault states, a fault diagnosis algorithm is developed, which is composed of multistate data processing (MSDP) block, subsection fluctuation analysis (SSFA) block, and the artificial neural network (ANN) block. First, the MSDP block is used to distinguish the different feature data and to adopt the data processing scheme, which improves the smoothness of the main data, retains the main fault features, and removes the influence of load change. Second, the SSFA block is used to extract the data feature, which can be used to accurately distinguish the different states of any switch. Finally, ANN is used by combining with the proposed MSDP and SSFA to implement intelligent classification, in which the dependency and the number of thresholds can be reduced. Comparing with the existing fault classification algorithms, the proposed algorithm is simple and stable to realize the multiple switches fault diagnosis for PV inverters. It does not require additional hardware equipment, and it can reduce the complexity of design and realization. Finally, the effectiveness of the fault diagnosis algorithm is verified by the experimental results. [ABSTRACT FROM AUTHOR]

The calibration, in particular about the installation errors of a star sensor, is a vital problem when improving the accuracy of stellar-inertial navigation system (INS). This paper proposed an all-parameter calibration method for a ground-based stellar-INS with 12-position rotations, using a Kalman filter that can simultaneously estimate bias, scale factor, misalignments of inertial measurement unit (IMU), and installation errors of star sensor. The difference between the star vector measured by the star sensor and the gold reference generated by the star simulator is used as an observation. On the basis of observability to all parameters, the accuracy is greatly enhanced through an iterative method. Better than previous separate calibration of INS and star sensor, the proposed method offers an advantage in that installation error is slightly influenced by IMU drift and device precision. The experimental results demonstrate that all estimated parameters have good stability and repeatability, with the maximum attitude error of integrated navigation less than 6^\prime \prime after compensation, compared with 20^\prime \prime using the traditional method. It is shown that the proposed calibration method can efficiently improve the navigation performance of stellar-INS, which has been extensively used in shipborne systems, military aircraft, and missile systems. [ABSTRACT FROM AUTHOR]

A new, simple, and high accuracy dual slope inductance-to-digital converter (DSIDC) suitable for differential reluctance sensors is presented in this paper. Differential reluctance sensors have two inductors that vary in a push–pull manner with respect to measurand. In many such sensors, the relationship between inductance and measurand is nonlinear. It is known that a small linear range can be obtained by taking the difference between the values of the sensor inductances. The proposed DSIDC accepts the sensor inductances having nonlinear characteristics and provides a linear digital output directly proportional to the measurand [without employing a dedicated analog-to-digital converter (ADC)]. The output of the DSIDC is linear for the full range of the sensor. As the output is in digital form, it can be easily stored and processed in a digital system. The DSIDC is based on dual-slope ADC principle and possesses many advantages. The effect of various parameters on the performance of the DSIDC was analyzed, quantified, and presented in this paper. A prototype DSIDC has been built and tested with a differential variable reluctance based displacement transducer. Output from the DSIDC was linear for the full range of input. [ABSTRACT FROM PUBLISHER]

This paper presents a new linearizing digital converter (LDC) that accepts output from differential type sensors with third-order polynomial transfer characteristics and provides a linear digital output proportional to the measurand. The LDC is realized using a modified dual-slope converter. Detailed operation of the proposed LDC, design procedure, and analysis of the effect of various circuit parameters on performance of the LDC are presented in this paper. The proposed methodology of LDC is also extended for sensors with second-order polynomial characteristics. The functionality of the LDC has been verified with the help of simulation studies. A prototype LDC has been developed and interfaced with a novel reluctance-Hall effect-based angle sensor (having a third-order characteristic) and tested. Test results show that the output of the overall transducer is linear across a wide range of angles, and thus underline the efficacy of the proposed scheme for differential type sensors with third-order transfer characteristics. [ABSTRACT FROM PUBLISHER]

A novel readout circuit for interfacing single element resistive sensors is presented in this paper. The proposed scheme is based on a new relaxation oscillator (RO). The RO, along with a timer counter provides a digital output proportional to the resistance of the sensor. The output characteristic of most of the existing readout circuits for resistive sensors suffers from gain, offset, and nonlinearity errors. The sources of errors include various nonideal circuit parameters and their drift. The output of the proposed readout circuit has a special feature that it is not a function of the circuit parameters such as: 1) offset voltages of the opamps and comparators; 2) bias currents of the opamps and comparators; 3) gain of various units employed; 4) ON-resistance of the switches; 5) value or mismatch in the magnitudes of the reference voltages employed; 6) delay of the switches and comparator; 7) leakage current of the switch; and 8) slew rate of the opamp. Such a scheme will be useful for high accuracy measurements, even when the parameters 1)–8) may vary or drift, due to variation in the measurement environment. A prototype of the proposed readout scheme has been developed in the laboratory and the performance has been evaluated under various conditions. The output was found to be linear with a worst-case nonlinearity of 0.05%. Test results from a prototype developed show that the proposed scheme possesses all the features, described above, as expected. [ABSTRACT FROM PUBLISHER]

The IEC technical report 61000-4-37 describes methods to verify that compliance systems to measure IEC 61000-3-2 and work within their specified tolerances. The waveforms required for these tests have a rich harmonic content. This paper describes a technique to produce these harmonics using a programmable microcontroller controlling an insulatedgate bipolar transistor. The results are shown and any differences between 61000-4-37 and the results are explained. [ABSTRACT FROM AUTHOR]

In the field of energy harvesting, it has been demonstrated that under the appropriate conditions, nonlinear configurations of the harvester can provide better performance, compared with linear resonant oscillators; the performance is quantified in terms of the amount of energy extracted from environmental mechanical or seismic vibrations. In this paper, the results of investigations on a system for energy harvesting from wideband vibrations, using a nonlinear snap-through-buckling configuration and two piezoelectric actuators, placed at the stable minima of the potential energy function that underpins the dynamics of the flexible beam are presented. A nonlinear model is proposed that can describe the device behavior when it is driven by a suprathreshold deterministic signal, a wideband noise, or a subthreshold signal superimposed onto a (usually bandlimited) noise background. In the latter case, the system is seen to exhibit the so-called “stochastic resonance” behavior. The bandwidth of the nonlinear energy harvester is about 15 Hz, which is compatible with vibrational energy sources at low frequencies, e.g., a walking human. The device is seen to generate power up to 160~\mu \textW when subject to a noise limited at 15 Hz. The power is sufficient to operate a standard wireless sensor node and the conversion efficiency of the harvester is about 12%. [ABSTRACT FROM PUBLISHER]

Applying pulsewidth modulation (PWM) to control the gain in audio codecs for mobile applications leads to several advantages, such as the smooth control of tuning parameters, smaller silicon area, and lower power consumption, as compared with other tuning techniques using programmable gain amplifiers and zero crossing detectors. The PWM has to be embedded into the main signal path, preferably in a closed-loop control scheme, in order to exploit its benefits. However, the insertion of dithering and offset controls in a gain setting loop poses the problem of controlling their effects in all gain conditions. This paper reports a novel technique aimed at solving the associated issues and limitations, and provides the experimental proof of the concept through the implementation of a test-chip design on silicon. In particular, this paper reports the design and experimental results of a delta–sigma analog-to-digital converter featuring a click-free gain control technique, dithering insertion, and idle-tone shifting, which has been implemented in a 40-nm complementary metal–oxide–semiconductor technology for commercial telecom audio codec applications. [ABSTRACT FROM PUBLISHER]

This paper presents a new, simple but effective, electronic method to obtain inverse-cosine of an electrical variable. The proposed method is very useful for linearization of sensors whose output is a cosine or sine function of the physical quantity being sensed. The inverse-cosine of the variable is obtained by comparing it with a reference sinusoidal wave. The proposed method is easy to implement using electronic components. Using the new technique, a giant magneto-resistance-based angle sensor that provides an output linearly proportional to the angle being sensed has been developed, and the details are reported in this paper. A prototype of the angle sensor has been built, and the practicality of the new method has been tested successfully. The developed sensor provides a linear output for a range of 0° to 180°. The worst case error was found to be less than 0.35° for a range of 10°-170°. [ABSTRACT FROM AUTHOR]

This paper presents a novel inductive loop sensor that can detect vehicles under a heterogeneous and less-lane-disciplined traffic and thus can be used to support a traffic control management system in optimizing the best use of existing roads. The loop sensor proposed in this paper detects large (e.g., bus) as well as small (e.g., bicycle) vehicles occupying any available space in the roadway, which is the main requirement for sensing heterogeneous and lane-less traffic. To accomplish the sensing of large as well as small vehicles, a multiple loop system with a new inductive loop sensor structure is proposed. The proposed sensor structure not only senses and segregates the vehicle type as bicycle, motor cycle, scooter, car, and bus but also enables accurate counting of the number of vehicles even in a mixed traffic flow condition. A prototype of the multiple loop sensing system has been developed and tested. Field tests indicate that the prototype successfully detected all types of vehicles and counted, correctly, the number of each type of vehicles. Thus, the suitability of the proposed sensor system for any type of traffic has been established. [ABSTRACT FROM AUTHOR]

Currently, many large and complex systems, such as telecommunication systems, power systems, and automated manufacture systems, require their distributed clocks to be synchronized to the master clock. This paper discusses implementation of a distributed embedded time-synchronized system, based on the IEEE 1588 standard. Two important requirements exist in time synchronization. One is that the clocks be synchronized at maximum speed. The other is that the clocks operate at optimum precision and accuracy over the long term. This paper proposes a switching controller, which combines a fuzzy control scheme and a traditional proportional integral (PI) control scheme to meet the aforementioned two requirements. The traditional PI control scheme was used in the steady state, whereas the fuzzy control scheme was adopted in the transient stage. The experimental results showed that in the fuzzy control scheme, transient time, which is the length of time in the transient state, was reduced to 50% of the transient time in the PI control scheme. [ABSTRACT FROM AUTHOR]

The frequency of a real sinusoid is often estimated by interpolated discrete Fourier transform (IpDFT) algorithms because of the high accuracy and low computational burden. However, conventional IpDFTs focus on frequency estimation when the number of acquired sine wave cycles (NASC) is more than two. Frequency estimation with the small NASC is applicable in manufacturing processes, radar level measurement, and other applications. The spectral leakage of the negative frequency (the image component) significantly distorts the positive frequency when the NASC is small, dramatically degrading estimation accuracy. In particular, it is a challenging task for existing IpDFTs to provide high estimation accuracy when the NASC is less than one. In this paper, a switch-based IpDFT is proposed to provide high frequency estimation accuracy for \text NASC < 1 . The theoretical variance of the algorithm in white Gaussian noise is formulated, which includes the upper bound and the lower bound. Computer simulations and real measurements are conducted to corroborate the theoretical analysis and to demonstrate that the proposed algorithm achieves better accuracy and antinoise capability for \text NASC < 1 than existing algorithms. [ABSTRACT FROM AUTHOR]

In this paper, a low-cost approach for polymer electrolyte membrane fuel cell (FC) drying and flooding diagnosis based on power converter ripple is presented, suitable to be implemented in commercial applications. If proper signal processing algorithms are employed, the high-frequency ripple inherently produced by switch-mode converters allows one to monitor the FC ohmic resistance, which is a good indicator for membrane drying, while an ad hoc switching control of the converter allows one to monitor also the low-frequency impedance, which is an indicator for cell flooding. This technique is tested with a dc/dc boost converter directly connected to a single cell, discussing how different FC operation modes (such as constant current or constant voltage) may affect the sensitivity required to the diagnostic algorithm to correctly recognize drying and flooding occurrences. [ABSTRACT FROM PUBLISHER]

This paper presents a novel digital converter for a contactless displacement transducer. The sensor part of the proposed transducer employs a floating (contactless) wiper that moves over a resistive element. A novel signal-conditioning circuit presented here operates on the contactless resistive potentiometer element and provides a digital output that linearly varies with the position of the wiper. The signal-conditioning circuit is developed such that the digital output is independent of the coupling capacitor that arises between the floating wiper and the resistive element, thus eliminating the effect of any jitter that may arise in the movement of the wiper. Results from a prototype circuit built and tested using a prototype sensor establish the efficacy of the proffered scheme. [ABSTRACT FROM PUBLISHER]

We have evaluated the linearity of commercial digital voltmeters (DVMs) using a programmable Josephson voltage standard (PJVS) system. The PJVS system is composed of a 524 288-niobium nitride-based Josephson junction array that has the ability to generate arbitrary output voltages up to 17 V with a resolution of 12 bits. In our system, the junction array is operated in a 10-K compact cooler without a liquid-helium coolant. Up to now, we have succeeded in generating accurate dc voltage levels of up to approximately 13 V using this system. In this paper, we demonstrate our PJVS system as a tool for investigating the linearity characteristics of commercial DVMs, with an accuracy level of 0.1 \mu \textV /V or better, and discuss the uncertainty sources in these measurements. [ABSTRACT FROM PUBLISHER]

In this paper, we present a novel technique for optical 3-D surface reconstruction by using line-scan cameras and structured light in combination. The approach generating structured light is customized to the special demands of line-scan image capturing. Owing to the distributed generation of light and the absence of shading elements, we obtain a light intensity that is comparable with conventional line lights. Thus, we achieve short integration times which is a necessary condition in most line-scan applications. Furthermore, with our approach we can generate different pattern sequences, which allows us to implement coded light methods such as time correlation or phase shifting. The light patterns can be switched synchronously with the captured lines of the camera. Thus, we are able to measure continuously whereby a single surface scan is sufficient to calculate a high-quality 3-D reconstruction. [ABSTRACT FROM PUBLISHER]

This paper presents the design and implementation of a rail-to-rail 460-kS/s 10-bit successive approximation register analog-to-digital converter (ADC) for the power-efficient capacitance measurement. The specifications of ADC are optimized at system level, emphasizing the ADC following a switched-capacitor capacitance-to-voltage (C2V) converter. To be compatible to the output of C2V, a bootstrap switch with body effect reduction is adopted to provide the rail-to-rail processing ability. The charge redistribution converter is implemented by a single-ended cascaded binary-weighted capacitive digital-to-analog converter (DAC). The total area of the DAC array is not only limited by the matching behavior but also by the noise performance of C2V. To relax the settling requirement and improve the power efficiency, self-timing technique is employed which borrows extra half clock period for open-loop settling of preamps. The balance between noise and power consumption of dynamic comparator with preamps is also considered. The ADC circuit was implemented in 0.18- \mu m CMOS technology and occupies an active area of 0.18 \mathrm{mm}^{2} . The tested prototype achieves a signal-to-noise-plus-distortion ratio of 54 dB and a spurious-free dynamic range of 68 dB. The integral nonlinearity and differential nonlinearity are 0.5 and 0.34 least-significant-bit, respectively. The total power consumption is 21 \mu $ W corresponding to 110 fJ/conversion-step figure of merit. [ABSTRACT FROM PUBLISHER]

A new automated permuting capacitor device (APCD) for calibration of inductive voltage dividers (IVDs) with four-terminal-pair definition was designed and tested. The permuting capacitors composed of 11-SMD capacitors were housed in a bulk metal in a symmetrical arrangement. Thus, the APCD is compact and the temperature of the APCD could be controlled within several mKs. Using coaxial microwave switches, the APCD was permuted quickly and automatically using electrical signals during the calibration process. This prevented the APCD from being thermally perturbed by manual operation. Owing to the improved stability of the device, the effects of stray capacitance and voltage coefficient of the APCD were evaluated accurately. The calibration of an IVD using the permuting capacitor method with this APCD in the frequency range 1–2 kHz with accuracy comparable with that of the straddling method is presented in this paper. [ABSTRACT FROM PUBLISHER]

This paper presents a power-aware instrumentation amplifier (IA) based on differential difference amplifier (DDA) dedicated to a resistive Wheatstone bridge sensor system. The design incorporates a proposed current source replica (CSR) circuit that facilitates the pair matching layout for all critical pairs in DDA input stage. This is in contrast with the conventional design where the stated layout technique can only be applied to the input transistor pairs. Besides, a new analysis on common-mode signals and differential common-mode signal in chopper-stabilized DDA is given. It has shown that the differential common-mode signal is not modulated in chopping DDA. The relationship between dc offset and differential common-mode rejection ratio (CMRRd) is illustrated. Enhancing CMRRd will lead to reduction of dc offset and offset drift in DDA. Fabricated by a 0.18- \mum CMOS process, the experimental results have shown that the maximum input-referred offset for the injection-nulling switch chopper DDA with CSR circuit is 3 \muV , while the input-referred dc offset is 1.78 \muV (mean $+$ standard deviation) at a chopping frequency of 10 kHz from eight fabricated samples. For a closed-loop gain of 40.17 dB, its output ripple is reduced by three times with respect to itself without CSR. The IA powered with a high-power supply rejection regulator has been tested with a resistive Wheatstone bridge. The transducer achieves an input-referred noise of 3.76 \mu{\rm Vrms} for 2-kHz bandwidth. [ABSTRACT FROM PUBLISHER]

The purpose of this paper is to improve the management of cables that need much time and work in the measurement environment that has many multichannel cables. Therefore, a monitoring system that inspects faults and connection states of multichannel cables is suggested and designed. The system is based on time-domain reflectometry (TDR) and has two features that distinguish it from the precedent researches. One of them is a hardware interface for the multipair cable, which is a channel distributor designed using a switch. The other is the TDR-signal analysis algorithm based on the database. In other words, the system can check a number of signal wires included in a multichannel cable automatically with one step. In addition, it is able to show results of the signal analysis immediately. The performance of such a system is verified through tests. As a result, it is shown that the monitoring system is fast and reliable and it provides a reasonable analysis result on the TDR signal. [ABSTRACT FROM PUBLISHER]

This paper proposes a simplified current sensing technique for the successful tracking of maximum power point with boost converter for photovoltaic (PV) power systems. To achieve the optimum solutions, the simplest sensing strategy is proposed with high resolution, maximum efficiency, and low cost. In general, PV current of a solar power system is obtained not in continuous time domain but in discrete one due to the digital signal processor-based controller. Instead of continuous resistive sensors, the improved method uses a bypass circuit to bypass the measuring current when the controller halts the sampling of the voltage across resistive sensor. To make this approach more efficient, current sensing process is set to flow through the resistor during some sporadically selected sampling period for responding the slow dynamic of the maximum power point transition. The bypassing approach can be further improved by removing the resistive sensor replaced to the bypass MOSFET. The proposed method contributes to the sensing loss reduction (the ultimate loss reduction is 97% of conventional resistive sensor) as well as to minimization of the thermal stresses on the sensor (23.2^\circC), which enables the proposed methods applied to middle range power conversion systems. Finally, the maximum power point tracking ability of the PV system is evaluated under a rapidly changing cloudy day condition and the superior performance of the proposed technique is demonstrated by comparing the results obtained using conventional current sensing method and proposed current sensing method. [ABSTRACT FROM PUBLISHER]

In this paper, the design of a new offset correction system employing a time-varying resistance as a probe for the detection of the sign and magnitude of the equivalent input offset of an operational amplifier in a series–shunt feedback configuration is presented. In order to considerably reduce the charge injection effects resulting from the switching of the MOS transistor that is used for the implementation of the time-varying resistance, we resort to a proper discrete time-sampling strategy for offset error detection. With respect to a previous topology, the new approach allows us to extend the useful amplifier bandwidth from a few hertz up to about 100 Hz with a gain boost from 201 to 1001. With the new approach, a residual offset on the order of a few tens of nanovolts is obtained, which allows us to classify the system as a nanovolt amplifier. [ABSTRACT FROM AUTHOR]

An efficient signal conditioning (SC) scheme that helps to obtain a linear output from a magnetoresistive (MR) angle sensor for 0^\circ–360 ^\circ range is presented in this paper. Most of the existing MR angle sensors have a sine/cosine relationship between the output and sensing angle, but a linear characteristic will be very useful. The new SC circuit of the proposed transducer accepts and processes output signals from an MR sensor that is sine/cosine in nature and gives an output directly proportional to the sensing angle. The sensitivity of the transducer output to variations in different circuit and mechanical parameters has been analyzed in detail, and their effect has been quantified. The functionality of the SC has been studied using SPICE simulations. A prototype of the proposed SC circuit has been built and tested using emulated sensor output signals. The output of the prototype circuit was linear from 0^\circ to 360 ^\circ, and worst case error was less than 0.08%. An angle sensor unit has been built using an MR sensor IC, interfaced to the SC circuit and tested. As expected, the output was found to be linear for a full-circle range. [ABSTRACT FROM AUTHOR]

In this paper, a digital switching demodulator is presented for use in ac-based electrical capacitance tomography systems. Implementing a switching phase-sensitive demodulator (PSD) digitally offers the following advantages: 1) Demodulation can be implemented using a programmable digital device, and hence, CMOS switches, which are used in a conventional switching PSD, are no longer needed; 2) compared with the widely used digital quadrature PSD, this proposed demodulator is simple in configuration because neither a reference signal nor multiplication is required; 3) according to the specific requirements, the new demodulator can be implemented in two operation modes, i.e., the amplitude mode and the phase-sensitive mode; and 4) because only subtractions and accumulations are needed, the proposed demodulator can be easily implemented with low-cost logic devices, e.g., a complex programmable logic device (CPLD). By simulation, the feasibility and effectiveness of the proposed demodulator have been confirmed. CPLD-based and field-programmable-gate-array-based capacitance measurement circuits are constructed, and the performances of different demodulation methods are compared. Both simulation and experiment show that the proposed demodulator can provide demodulation results with high signal-to-noise ratio. The system design can be simplified using the digital switching demodulator. [ABSTRACT FROM AUTHOR]

It is very important to be able to predict the amount of the power losses related to the power switches with good accuracy in the design phase of power converters since a poor estimation can considerably extend the time needed for the development of the devices. This paper illustrates a method to calculate with satisfactory accuracy the power losses in power converters, based on the measured switching currents and voltages of semiconductor devices. It represents a further development and an improvement of previous studies and includes an automatic compensation of voltage and current offsets. Experimental measurements of the conduction voltage drops of insulated-gate bipolar transistors and diodes have been performed and compared with manufacturer's data to validate the method. The method was then applied to a power converter chosen as representative, using the experimental data as input. The results are reported and discussed. [ABSTRACT FROM PUBLISHER]

The International Electrotechnical Commission (IEC) 61850 standard is widely used in substation automation system (SAS), even if some aspects related to the network-based time synchronization are still under investigation. The latest version of the IEC 61850 standard introduces IEEE 1588 Precision Time Protocol (PTP) for distributing time in the station and process buses, in addition to the previously used Simple Network Time Protocol (SNTP). Some time synchronization problems may arise when mixing old and new IEC 61850 devices in the same system; the IEEE 1588 PTP and SNTP technologies have somewhat different time representations and synchronization schemes, requiring time gateways for smooth integration. This paper introduces and compares the performance of some compact time gateways with different implementation architectures. All the examined gateways have the same external structure: They are transparent two-port devices which are inserted in the last network link between the switch and the end device, in order to perform the time conversion from IEEE 1588 PTP to SNTP. The time gateways are built using the same hardware platform based on a Field Programmable Gate Array that enables the creation of real embedded prototypes. The experimental results show that all the considered time gateways are applicable to SAS, but some of them have better performance than others in terms of synchronization accuracy. Moreover, the authors identify the bottleneck in the SNTP implementation of the time gateway architecture. A careful analysis of the behavior of SNTP is proposed, and useful suggestions for trading off between synchronization accuracy and time gateway complexity are given. [ABSTRACT FROM AUTHOR]

This paper presents an in situ moisture content sensor based on a switched-polarization dipole antenna that detects the magnitude of mutual coupling between perpendicular and parallel polarizations. Three aspects of the sensor development are presented: a new closed-form calculation of mutual impedance of perpendicular polarization dipole antenna, an antenna design, and an investigation of performance enhancement. As the sensor detects only the magnitude of mutual coupling, it is low cost and low profile and needs less processing time. Thus, it is suitable for a closed-loop drying system. Our study has shown that the values of the dielectric constants measured by this sensor are comparable to the reference values from the transmission line technique in the previous work. However, there are significant differences in the values of the dielectric loss factors because the structure of the presented sensor is not a closed boundary like the transmission line sensor. Therefore, error compensation has been developed to correct the results. This sensor, in a closed-loop drying system, has shown good performance for in situ monitoring and real-time monitoring. Consequently, it is very suitable for monitoring the moisture content of paddy (rough rice). [ABSTRACT FROM AUTHOR]

This paper presents a power-efficient capacitive-sensor interface solution for high-speed and high-resolution subnanometer displacement measurement systems. The proposed solution utilizes a zoom-in capacitance-to-voltage converter stage to remove the offset posed by the large nominal sensor capacitance, which would otherwise dominate the dynamic range. The realized zoom-in factor is 100. The designed circuit uses a correlated-double-sampling technique to cancel both the amplifier offset and the reset noise. First, a printed-circuit-board solution was realized to verify the principle of operation and its limitations. Then, an integrated circuit was designed, fabricated, and tested. Measurement results show that the achievable capacitance resolution is better than 30 aF, from a sensor with a nominal capacitance of 10 pF, which translates into a dynamic range of 18 b. The measurement latency is only 5 \mu\s. This performance is achieved with only 2.4-mW power consumption. [ABSTRACT FROM AUTHOR]

Many low-power successive approximation register analog-to-digital converters (ADCs) use separate small capacitors, instead of the entire charge scaling (CS) capacitor arrays, to sample the analog inputs. While reducing power consumption, it makes these ADCs prone to gain errors and input range reduction caused by parasitic capacitance of the CS array. This paper presents an effective technique with negligible hardware overhead to address this problem. Simulation results are also presented to validate the proposed technique. [ABSTRACT FROM PUBLISHER]

The correlation image sensor (CIS) is used in a variety of applications which involve the extraction and measurement of low-amplitude-modulated light signals from background interferences. Many applications have been reported on measurement of ac magnetic flux, interferometry, eye gaze tracking, and indirect 3-D imaging using these sensors. In this paper, the performance of different derivatives of the CIS is analyzed, and some modification is applied to the CIS to significantly increase its sensitivity at higher frame rates and reduce its output error. The effect of undesired parameters, such as parasitic capacitances, device mismatches, charge transfers, random noise, and temperature variations, is studied, and modified architectures are proposed to reduce them. The maximum demodulation frequency is also shown to be increased compared to original CIS. The presented designs are compared with previous solutions under similar operating conditions using a 0.35-\mu \m standard CMOS technology. It is shown that the designs can be used to detect lower modulated signal levels over a wider background dynamic range. [ABSTRACT FROM PUBLISHER]

Remote monitoring has been implemented in many areas. This paper introduces its specific application to a three-phase 10-kVA energy-efficient switchable distribution transformer. A designed embedded system and embedded Ethernet have been implemented to achieve a compact remote condition monitoring for the transformer. The embedded system performs acquisition of voltages, currents, and temperatures, controls the switching devices that connect the tappings of the transformer, and processes acquired data. Client and server applications were developed through the use of embedded Ethernet to enable remote monitoring through a local area network (LAN). Some protocols were developed as parts of software development of the whole system. Experimentation was done by applying the remote monitoring system to the transformer connected to three-phase variable supply voltage and load. Results of the experimentation by using a LAN available in the school revealed that the system can handle remote monitoring and control tasks for the transformer. [ABSTRACT FROM PUBLISHER]

This paper presents a front-end circuit with pulsewidth modulation (PWM) output for a capacitive sensor interface. A single-MOSFET-based capacitance-ratio-modulated current (CRMC) circuit is proposed to transform the sensed capacitance into a current proportional to a capacitance ratio. The proposed single-MOSFET-based CRMC circuit not only saves a lot of chip area but also lowers power consumption. Then, a dual-slope integration circuit transforms further the modulated current into PWM output. A prototype chip is designed and fabricated with a 0.35- \mu\m complementary metal–oxide–semiconductor process and has a core area of 0.09 \mm^2. The measurement results of the prototype chip demonstrate an accuracy value of up to 9.3 bit with 54- \mu\W power consumption. The microwatt power consumption and the small chip area of the proposed front-end circuit make it very suitable for a capacitive sensor interface in smart sensor chips. [ABSTRACT FROM PUBLISHER]

A new inductance comparator bridge has been constructed at the Institute of Measurements, Electronics, and Automatic Control (Gliwice, Poland) for the calibration of inductance standards in the frequency range of 100 Hz–10 kHz. Since the instrument belongs to the class of unbalanced transformer bridges, very accurate measurement of the voltage on the diagonal of the bridge is required. A vector voltmeter which enables the precise measurement of both components of the unbalance voltage is described in this paper. We report on the realization and characterization of the voltmeter which is an integral part of the new inductance comparator bridge. [ABSTRACT FROM AUTHOR]

This paper reports on a broadband dc ground isolated 20-Ω absorber for powers of up to 20 W. The realized absorber achieves reflections (referenced to 20Ω) below-10 dB over almost two frequency decades from less than 50 MHz to 2 GHz. It can be used as load resistor in the characterization of power amplifiers, particularly switch-mode ones, where broadband non- 50-Ω loads are required for measurement purposes. An additional advantage is that no bias-T is needed with this solution. This reduces measurement uncertainties due to the parasitics of the bias-T. Using the distributed concept offers a generic technique to realize such loads and also for other impedance values and other applications. [ABSTRACT FROM AUTHOR]