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The benefits of employing multilevel pulsewidth-modulated (PWM) waveforms for diagnostic purposes compared to sinusoidal- and square-shaped voltages are presented in this paper. Examples on how the high voltage circuits are designed to enable these studies, as well as results, are discussed. To demonstrate the approach, it is investigated what influence the choice of PWM levels has on the partial discharge (PD) characteristics for two similar wire specimens insulated by different materials. Here, to resemble a motor winding, two different twisted pair test objects insulated by either pure polyamide-imid (PAI) material or with added conductive Cr2O3 material were exposed to voltages with ultrashort rise times. The test objects were fed from either two-, three-, five-, or seven-level inverter waveforms of similar shape as in actual applications. To compare the performances, measurements of the PD characteristics were conducted. Specifically, the total number of PDs, as well as their average maximum amplitude per cycle, was obtained together with the phase-resolved PD pattern for each case. The experimental results presented in this paper show that the total peak and summed PD magnitude (exposure) drop considerably more for the Cr2O3 insulation compared to PAI when applying a five-level or higher level inverter. This reduction is more significant for the insulation with added Cr2O3 material and the usage of higher inverter levels reveals this. As more information can be obtained using higher inverter levels, the evaluation of new material constitutions is preferably done utilizing at least a three-level inverter or higher. [ABSTRACT FROM AUTHOR]

The availability of real-time information about the biological activity is a valuable matter in wastewater treatment employing activated sludge processes, and this is represented by the oxygen uptake rate (OUR). In these processes, OUR measurements have been used as a fast indicator of changes in waste load or influx of toxic organic compounds and for monitoring of the process efficiency. In this paper, we propose a method for OUR estimation by using Kalman filters and PWM control of the dissolved oxygen (DO) concentration in the activated sludge reactor. The proposed method presents a shorter response time than the standard online procedure and a lower measurement uncertainty compared to a previous feedback control method, which estimates the OUR from values of the applied control signal and the DO concentration measurements. Simulations are presented to illustrate the method and experiments are performed in a bench scale activated sludge reactor to show the applicability of the proposed estimator in a real system. The results confirm the fast response of the proposed method and its consistency with respect to the standard procedure for OUR computation. [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 presents an effective approach to the fault diagnosis of pulsewidth modulated (PWM) DC–DC power converters. It is based on a multilayer multivalued neuron neural network with a complex QR decomposition. This network is used to identify the parameter values running out of tolerance range in two topologies of PWM DC–DC converters, namely, the buck and boost circuits. The proposed technique is based on measurements of steady-state voltages and currents waveforms. [ABSTRACT FROM AUTHOR]

In this paper, a gray-scale CMOS image sensor (CIS) characterization system with an optimization feature has been proposed. By using a very fast and precise control of light intensity, based on the pulsewidth-modulation method, it is avoided to measure the illuminance every time. These features accelerate the multicriteria CIS optimization requiring many thousands of measurements. The system throughput is 2.5 Gb/s, which allows for capturing images from large arrays of the size $3000 \times 3000$ pixels at the rate of 25 frames/s, or small arrays ($128 \times 128$) at the rate of 15 000 frames/s. The efficient transfer of measurement data to the external software allows immediate presentation of optimization results in 3-D plots. The system automatically measures nonuniformity, spatial noise, temporal noise, signal-to-noise ratio, dynamic range, nonlinearity and image lag. A flat diffuser has been proposed as a cheaper alternative to an integrating sphere. This optical front-end is particularly useful for testing prototype CISs and vision-chips implemented in standard CMOS technologies as low- or medium-dynamic-range imagers. [ABSTRACT FROM AUTHOR]

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]

Nonlinear analog-to-digital conversion in smart sensor applications is an important topic since signal digitization and linearization can be performed in a single step near the transducer. In this paper a double pulsewidth modulated (PWM) scheme for nonlinear analog-to-digital conversion is presented. Calibration or auto-calibration data stored in the smart sensor's memory define the nonlinear profile characteristic of the transducer and provide the required data to obtain the inverse function of the analog-to-digital converter (ADC) transfer curve. Basically, as a function of the transducer's nonlinearity degree, the input voltage range of the ADC is segmented in a continuous set of subintervals and, for each of these subintervals, a second-order correction term based on a PWM A/D conversion is used to obtain a linear characteristic for the smart sensor. Additional advantages of this method result from its easy implementation in low-cost microcontrollers that include generally comparator inputs and PWM outputs. A flexible and programmable A/D conversion solution can be dynamically adapted to variations of the transducer's nonlinearity profile, and an increased resolution can be achieved at the expense of a lower conversion rate. Some MATLAB simulations and experimental results obtained with a square-root airflow transducer will be presented in the final part of the paper. [ABSTRACT FROM AUTHOR]

An approach to mass measurement for the electronic balance based on continuous-time sigma-delta (CT $\Sigma -\Delta $ ) modulator is described in this paper. As an effect of multifarious interfering noises, the accuracy of the electronic balance is restricted. The general idea of this proposed approach is to apply an electromagnetic-force-compensated load cell (EMCC), a related signal processing circuit, and a composite filter. The circuit mainly consists of a proportional-integral–differential controller and a pulsewidth modulator, which combine with the EMCC to form a CT \Sigma -\Delta $ modulator. As the CT \Sigma -\Delta $ modulator possesses inherent antialiasing filtering, oversampling, and noise-shaping characteristics, the interfering noises can be effectively removed by the composite filter that is composed of two filters. The simulations for both of the electronic balance models adopting the proposed approach and working in conventional pulse current mode are analyzed by adding the white Gaussian noise in Simulink. The simulation results demonstrate the effectiveness of this proposed approach, the proposed electronic balance in the field can improve its signal-to-noise ratio, and the testing results meet the requirement for the weighing accuracy of the special-class scale defined by Organisation Internationale De Métrologie Légale R76 nonautomatic weighing instruments. [ABSTRACT FROM PUBLISHER]

The determination of the efficiency of an electric motor or an inverter in an electric vehicle requires power measurements on the ac side of the inverter. Voltage and current signals arise there from the switching operation of the inverter and are therefore hardly bandlimited. The finite bandwidth of measurement devices, like sensors or ADCs, yields to a bandwidth limitation of the measured signals. This limitation modifies the measured signals and has an effect on the calculated power. Measurement uncertainty considerations require the evaluation of the relation between this bandwidth limitation and the resulting error in the power measurement. This relation allows then for evaluating the significance of the spectral components for the power calculation and the decision which components are relevant and must not be filtered out by a bandwidth limitation. This paper presents an evaluation method for determining the bandwidth limitation error and identifies critical quantities in a numerical study. [ABSTRACT FROM PUBLISHER]

When estimating the input-output characteristic of a static nonlinear function, input-referred noise may induce estimation bias, if model identification based on simple averages of input and output measurement data is performed. This paper considers estimation of static nonlinearities based on polynomial functions and input-output averaged data. It first illustrates how the estimation bias originates and then it describes a procedure to compensate its effects. Both simulation and experimental results are shown. Experiments are carried out to estimate the voltage-to-voltage characteristic of a diode-based electrical circuit. Practical considerations are made regarding the minimum number of samples needed to perform compensation effectively. [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]

A resistance to pulse width converter with improved stability and temperature compensation is described. The converter is therefore suited as a signal conditioner for resistive sensors. The sensor interface is based on a multivibrator in monostable or astable configuration and combines the single point calibration used in direct sensor-to-microcontroller interface. Analyses show that a resolution better than 14.2 b (for 20 MHz time base) with maximal relative error of 0.11% in the range 1000–3000 \Omega is achievable. In this paper, a comparative analysis in terms of measuring uncertainty, speed, and resolution between the multivibrator in monostable and astable operation is performed. A method for defining optimal time constant that results in best speed/resolution trade-off is proposed. [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]

This paper describes a system for the simultaneous dynamic control and thermal characterization of the heating and cooling phases of an ultralow-power (ULP) micromachined sensor, featuring thermal characteristics that are quite similar to those of innovative ULP semiconducting metal–oxide gas sensors. A pulsewidth-modulated (PWM) excitation system has been realized using a microcontroller featuring an ARM7 core to characterize the thermal behavior of a device formed by a Pt microheater and a Pt temperature sensor, over an insulating membrane. Three operating modes, i.e., constant target heater resistance, constant heating power, and cooling phase monitoring, were implemented. Objectives of the research were to analyze the relation between the time period and duty cycle of the PWM signal and the operating temperature of such ULP micromachined systems, to observe the thermal time constants of the device during the heating and cooling phases, and to measure the total thermal conductance. Experiments indicated that an approximately constant heater temperature in the constant target heater resistance regime (i.e., after the initial thermal transient due to the heating algorithm) can only be obtained if the time period of the heating signal is smaller than 50 \mu\s, i.e., much faster than the time constant of the device. Constant power experiments show quantitatively a unique time constant \tau for both the heater and the temperature sensor (T-sensor) in the heating phase (with a known applied power) and the cooling phase (with zero power). This time constant decreases during heating in a range of 2.3–2 ms as a function of an increasing temperature rise \Delta T between the ambient and the operating temperature. Moreover, we observed that, in the chosen operating temperature range, the thermal conductance is a linear function of \Delta T. Finally, repeatability of experimental results was assessed by guaranteeing that the standard deviation of the controlled temperature was within \pm 5.5\ ^\circ\C in worst-case conditions. [ABSTRACT FROM PUBLISHER]

The efficiency of light-emitting-diode (LED) lights approaches that of fluorescent lamps. LED light sources find more applications than conventional light bulbs due to their compactness, lower heat dissipation, and real-time color-changing capability. Stabilizing the colors of red-green-blue (RGB) LED lights is a challenging task, which includes color light intensity control using switching-mode power converters, color point maintenance against LED junction temperature change, and limiting LED device temperature to prolong the LED lifetime. In this paper, we present a LED junction temperature measurement technique for a pulsewidth modulation diode forward current controlled RGB LED lighting system. The technique has been automated and can effectively stabilize the color without the need for using expensive feedback systems that involve light sensors. Performance in terms of chromaticity and luminance stability for a temperature-compensated RGB LED system will be presented. [ABSTRACT FROM AUTHOR]

This paper presents the implementation of variable-delay random pulsewidth modulation (VD-RPWM) for an automotive traction drive inverter. RPWM is desirable as a means of reducing electromagnetic emissions from the inverter and minimizing electromagnetic-compatibility filtering requirements. It can also serve in reducing acoustic noise generated by the drive. The algorithm is implemented on a power-PC-based microprocessor. Experimental results are presented to verify the operation of the algorithm and its compatibility with basic motor-control functions. Spectrum plots of the phase current and voltage demonstrate the effectiveness of the technique in mitigating electromagnetic interference. The effects on torque ripple and acoustic noise are also investigated. [ABSTRACT FROM AUTHOR]