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Wireless sensor networks (WSNs) are technologies that play an important role in Internet of Things (IoT) systems. In most applications, sensor nodes are expected to operate for extended periods without maintenance. Therefore, minimizing power consumption and self-sustainability based on energy harvesting (EH) still represent important research challenges. In this article, a power management strategy (PMS) based on the weighted order statistics (WOS) classification technique is proposed to dynamically adapt the duty cycle of the sensor node according to historical data measurements. Unnecessary acquisition and transmission of slow-varying signals are reduced, improving the power consumption of the node. As traditional renewable sources (sunlight, wind, and vibration) are scarce in indoor scenarios, an array of Dypsis Lutescens plants is used as a power bioenergy cell, providing a clean and cost-effective alternative to power indoor sensor nodes. The WOS technique is programmed into an nRF52840 microcontroller, and an ultralow-power BQ25570 harvesting circuit harnesses the energy from the array of plants. Experimental results include the energy performance analysis of the wireless sensor node and the measured power generation capacity of the bioenergy source, showing an energy-autonomous behavior for IoT applications. Average power consumption of 15.6 mW per transmitted data packet of 14 bytes is achieved, which represents the ability to perform at least 693 data transmissions per day considering an 8 F supercapacitor as a storage device. [ABSTRACT FROM AUTHOR]

This article presents a method to obtain a enhanced frequency resolution two-phase lock-in amplifier (LIA) with two channels in a microcontroller using minimum external circuitry. The timer peripheral of the microcontroller was used to generate the square wave signals for both the excitation and the quadrant demodulation, simplifying the waveform synthesis when compared to the use of digital-to-analog converters (DACs). To improve the frequency resolution of the generated signals, the timer signal was dithered to achieve fractional frequency values, while demodulation was executed in real time with signal acquisition. The real and imaginary parts of the signal are then transmitted to the computer by the universal serial bus (USB) interface while the computer sends commands to change the frequency, phase, or control other features. As proof of work, quartz tuning fork (QTF) sensors were measured due to its high $Q$ -factor. The bandwidth of the lock-in was limited by the acquisition and demodulation sample rate of 300 Ks/s, while we showed 1000 times frequency resolution enhancement when compared to the not dithered signal generation. This approach can be applied in embedded design to measure frequency-dependent sensors with high $Q$ , in scientific instrumentation such as scanning probe microscopes (SPMs), or even for educational purposes to teach the working principle of the LIAs. [ABSTRACT FROM AUTHOR]

Electrocardiogram (ECG) is one of the most useful medical examinations for the monitoring of cardiovascular diseases. The position and the duration of the QRS complex on the ECG signal are very important in the diagnosis of these diseases. Even though several R-peak (and hence QRS complex) detection algorithms are available, most are based on complex computations that require off-line processing on a personal computer (PC). However, with the advances in wearable devices and telemedicine, an algorithm that can run efficiently on a microcontroller (or embedded system) is needed. This article presents the development of an embedded algorithm for the detection of the QRS complex of an ECG signal. The algorithm is based on the shape and appearance of the signal. It extracts certain characteristics like the shape of the QRS complex, its slope, trend, and the duration between two successive QRS complexes, and then use them to increase detection accuracy. First, the R-peak is detected through the application of three levels of tests using adaptive thresholds. Second, from each R position, the positions of Q and S are detected using three other tests. To evaluate the performance of the algorithm, the MIT-BIH database was used and the sensitivity, positive prediction, and F1 score were used as evaluation metrics. The algorithm obtained average F1 scores of 99.67%, 99.73%, and 99.83% for the MIT-BIH Arrhythmia, Pacemaker Rhythm, and the Normal Sinus Rhythm Databases, respectively. Both normal and abnormal ECG signals were used in this performance test. The algorithm was then implemented on a microcontroller system, and its accuracy and run time were evaluated. The obtained F1 score results were the same as on the personal computer (PC) and an average run time of $16.23~\mu \text{s}$ per sample was obtained. The performance of the algorithm was also compared to other commonly used algorithms. The proposed algorithm has great potential in wearable systems for long-term monitoring. [ABSTRACT FROM AUTHOR]

In this article, we present a novel autocorrelation-based frequency estimation algorithm for single-tone sinusoidal signals. In comparison to other state-of-the-art frequency estimation methods, the proposed one provides a better tradeoff between accuracy, complexity, and estimation range. In particular, the algorithm is able to achieve the Cramer–Rao lower bound for moderate and high signal-to-noise ratio, and its implementation is feasible even in resource-constrained microcontrollers, as those commonly used in the Industrial Internet-of-Things (IIoT) applications and low-cost instrumentation. Finally, we investigate the performance of the algorithm in the case of a practical IIoT application, i.e., frequency estimation of unbalanced three-phase power systems, showing that it outperforms several other autocorrelation-based estimators. [ABSTRACT FROM AUTHOR]

This article deals with the development of a resource-constrained activity detection algorithm for microcontroller-based wrist-worn devices. The various market available activity detection devices lack adequate agility and ease of use in certain applications, as they heavily rely upon computationally intensive algorithms to detect physical activity and step count. Therefore, by extension, they always need to stay connected with a smartphone that can perform these computations. To address this problem, this article introduces a standalone wearable device with the simplified algorithm for activity detection in a human being. The developed system consists of microelectromechanical systems (MEMS) triaxial accelerometer connected to a low-power microcontroller with a wrist anchor-able form factor. The step detection algorithm uses a moving average threshold filter to detect the change in acceleration data to identify specific events. A detailed comparative study considering power consumption and the step detection made between the developed device (with the resource-constrained algorithm) against market available devices shows that the average detection error of the developed algorithm is approximately 2% under various test conditions (i.e., walking, fast walking, and running) and has an accuracy of 94.96% for activity detection. This study reveals that the use of the proposed algorithm for activity detection not only brings down the cost of the overall device but also reduces the power consumption (< 45.7 mW) with a minimal covering size (12.56 cm2) for the wearable part that can extend the application area of such devices. [ABSTRACT FROM AUTHOR]

As a real boost to competitiveness and productivity for sectors, such as health, agriculture, or industry 4.0, the Internet-of-Things (IoT) market is transforming business models and revolutionizing practices. A major challenge is to develop applications with high computing potential with limited resources. To satisfy both high-level performance and low-power requirements, a deep characterization method for microcontrollers is proposed since selecting the appropriate device is a central pillar of smart energy policy. The high-level analysis investigates the potential of various low-power microcontrollers with a benchmark utilizing a periodic duty cycle model of typical WSN applications. Afterward, deep characterization was carried out in two steps. The preselection phase is based on estimation whose results will serve as input for the second measurement phase. A highly accurate four-wire measurement involving guarding and shielding of all interfaces and the measurement cave is used for all measurements. To make the results comparable, a normalized power, defined as a measure of power per throughput, is introduced. The measurement characterizes the active power consumption depending on the supply voltage and frequency as well as sleep power, data logging power, and peripherals power. [ABSTRACT FROM AUTHOR]

Systems using microcontrollers make the interface of a transducer with the digital world much easier. They build smart, lucid, compact, cheap, and less power consuming electronic interfaces. Limited acquisition time is critical for many industrial applications. Single-element resistive sensors are used on a large scale. An attempt has been made to reduce the acquisition time of the measuring system compared to the existing work which converts the change in sensor resistance to the change in time with three charge–discharge cycles. Efforts have been made in this paper to reduce this to two charge–discharge cycles. The proposed work also compensates the errors due to lead wire resistance, the change in lead wire resistance, port pin resistances, and varying ambient temperature with reduced acquisition time. The mean of absolute errors, standard deviation, integral squared error (ISE), nonlinearity, and hysteresis of the proposed method have been computed. Simulation and experimentation study of the proposed system provided encouraging results. The mean of absolute errors and standard deviation of the proposed method in the simulation were 0.07 and 0.08 $\Omega $ , respectively. Furthermore, during experimentation, the values of the mean of absolute errors and standard deviation were 0.11 and 0.11 $\Omega $ , respectively. ISE was found to be 0.09 and 0.19 in simulation and experimentation, respectively. The proposed two-cycle method has an acquisition time of only 60% of the three-cycle method with no reduction in performance. [ABSTRACT FROM AUTHOR]

The measurement of the analyte concentration in electrochemical biosensors traditionally requires costly laboratory equipment to obtain accurate results. Innovative portable solutions have recently been proposed, but usually, they lean on personal computers (PCs) or smartphones for data elaboration and they exhibit poor resolution or portability and proprietary software. This paper presents a low-cost portable system, assembling an ad hoc-designed analog front end (AFE) and a development board equipped with a system on chip integrating a microcontroller and a Wi-Fi network processor. The wireless module enables the transmission of measurements directly to a cloud service for sharing device outcome with users (physicians, caregivers, and so on). In doing so, the system does not require neither the customized software nor other devices involved in data acquisition. Furthermore, when any Internet connection is lost, the data are stored on board for subsequent transmission when a Wi-Fi connection is available. The noise output voltage spectrum has been characterized. Since the designed device is intended to be battery-powered to enhance portability, investigations about battery lifetime were carried out. Finally, data acquired with a conventional benchtop Autolab PGSTAT-204 electrochemical workstation are compared with the outcome of our developed device to validate the effectiveness of our proposal. To this end, we selected ferri/ferrocyanide as redox probe, obtaining the calibration curves for both the platforms. The final outcomes are shown to be feasible, accurate, and repeatable. [ABSTRACT FROM AUTHOR]

This article describes the development and experimental verification of an instrument fault accommodation (IFA) scheme for front and rear suspension stroke sensors in motorcycles equipped with electronically controlled semiactive suspension systems. In particular, the IFA scheme is based on the use of nonlinear autoregressive with exogenous inputs (NARX) neural networks (NNs) employed as soft sensors for feeding the suspension control strategy back with measurement even in the presence of faults occurred on the sensors. Different NN architectures have been trained and tuned by considering real data acquired during several measurement campaigns. The performance has been compared with that of the well-known half-car model (HCM). Very satisfying results allow the soft sensor to be really integrated into fault-tolerant control systems. In experimental road tests, an implementation of the proposed IFA scheme on a low-cost microcontroller for automotive applications showed to be in real time. In this article, these experimental results are shown to prove the good performance of the IFA scheme in different motorcycle operating conditions. [ABSTRACT FROM AUTHOR]

In this paper, it is a low-cost device that is able to determine the concentration of Saccharomyces cerevisiae cells based on the methylene blue reduction rate. The device, composed by laser diodes at 650-nm, 10-mm cuvette, photodetectors, and a microcontroller, is able to measure cell concentrations between 106 and 109 cells/ml. The mean error was 3.77% and 2.75% comparing with the yeast plate count protocol and the Neubauer chamber’s count protocol, respectively. Also, the device does not need specialized personnel to be operated and it can be used in breweries and industrial processes. [ABSTRACT FROM AUTHOR]

In the past years, strong changes of power network architectures and operation have led to make use of huge quantities of instrumentation, spread around the grid. In fact, there is a strong need to perform very accurate measurements of electrical quantities in many nodes of the network, mainly due to the strong penetration of distributed generation. Recently, the main Italian utility has also asked for such kind of instrumentation. Its main feature must be to perform accurate measurements in all actual conditions. Such conditions include the instrumentation operation during the off-nominal condition of the network. To this purpose, in this paper, a low-cost acquisition system (AS) developed by the authors is recalled. Then, a full comparison with off-the-shelf products during ideal or not power source is provided. The obtained results highlight the potentialities of the developed system for its implementation in both laboratory or medium-/low-voltage (MV/LV) networks. [ABSTRACT FROM AUTHOR]

This paper proposed a wireless real-time pH monitoring system. This system was associated ruthenium dioxide (RuO2) membrane pH sensor, microcontroller, liquid-crystal display (LCD), C/C++ program, and WiFi communication module to develop and use for ecosystem monitoring in the future. The ruthenium dioxide thin film of the pH sensor was deposited onto indium tin oxide (ITO) and polyethylene terephthalate (PET) substrates by the radio frequency (RF) sputtering system. The surface morphology of RuO2 thin film with scanning probe microscopy (SPM) was investigated. The electrochemical impedance analysis of RuO2 thin film was also studied. [ABSTRACT FROM AUTHOR]

This paper describes the implementation and experimental verification of an instrument fault detection (IFD) scheme for stroke sensors. In the scheme, a nonlinear autoregressive with exogenous inputs (NARX) neural network works as a soft sensor for the generation of residuals, while a rule-based decision maker provides the fault detection and classification. The scheme was thought to be implemented in the firmware of central units for the control of semiactive suspension systems for motorbikes. Execution times compatible with the real-time application constraints are reached through straightforward programing rules and suitable code optimization. These times were obtained with machine parameter values (such as clock frequency and absorbed current) far below the upper limit of the range, thanks to the adoption of a programing methodology specially designed for the real-time implementation of diagnostic schemes on general-purpose microcontrollers (MCUs). The diagnostic performance of the scheme was verified through an experimental campaign, carried out on a motorcycle featured with electronic controlled semiactive suspensions. Promptness and reliability in detecting the most common faults of the rear stroke sensor resulted fully compatible with actual applications’ expected values. [ABSTRACT FROM AUTHOR]

This paper presents a low-cost interface circuit for lossy capacitive sensors. Most of the capacitive sensors are lossy in nature, where the resistance value of the sensor significantly varies along with the capacitance value. Accurate measurement of those values of a lossy capacitive sensor is a challenging task. This paper deals with the development of an electronic interface circuit for such a capacitive sensor. The circuit is based on the measurement of quadrature and in-phase components of the signal. To extract the actual value of the capacitance and the resistance, an average of the quadrature and the in-phase components of output is required. This is implemented using a microcontroller and provides flexibility in averaging (e.g., adjustable length of data to be processed). A PCB of the circuit has been fabricated and tested in the laboratory using capacitors and resistors with known values. The accuracy of the circuit was better than 0.6% and −2.2% for the measurement of capacitance and resistance, respectively. Also, the circuit is highly linear (FS nonlinearity of 0.32%) for a wide range of capacitance measurement (162 pF–3.680 nF). To confirm the effectiveness of the circuit, it was interfaced to a lossy capacitive humidity sensor and another capacitive transducer to measure the dielectric constants of edible oils. The results were compared with a precision impedance analyzer (Agilent 4294A); the maximum relative error was noted as ±1.6% in the measurement of permittivity values of edible oil. The prototype developed has the option to easily adjust the sensitivity and operating range, depending on the application. [ABSTRACT FROM AUTHOR]

This article proposes, analyzes, and tests a wake-up circuit for a microcontroller (MCU) that uses a light-emitting diode (LED), operating as a photodetector, illuminated by a smartphone flashlight. The wake-up circuit consists of a high-pass filter and a voltage-level translator that interfaces the LED, with a suitable resistor in parallel, to the MCU. When illuminated by a switching flashlight, the LED generates a square voltage that is conveniently converted in logic levels at the output of the wake-up circuit. A firmware embedded into the MCU additionally checks that a predetermined sequence of logic pulses at a given rate is accomplished to activate the MCU. This article includes a theoretical analysis and experimental results that validate the proposed circuit. [ABSTRACT FROM AUTHOR]

An on-chip instrument for measuring ex post the drug actually released by transdermal delivery is proposed. The volume of a drug conveyed through the skin is assessed by measuring the bioimpedance locally before and after delivery. In therapeutic applications, the instrument can provide a low-cost and clinically portable solution. In the first part of this paper, the concept and physical design of the instrument as well as details about its realization and operations are illustrated. Then, the metrological characterization, using injection as a reference subcutaneous transfer of a known volume of drug, is reported in laboratory, in vitro on eggplants and ex vivo on pig ears. Results of resolution, short-term stability, interindividual tissue reproducibility, sensitivity, repeatability, and linearity point out noteworthy scenarios of clinical applications. [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]

The measurement of fluid and rock properties within oil and gas wells is critical to efficient hydrocarbon production. These data are generally acquired by wireline logging, where sensors are lowered into the well at the end of a long cable. The handling of this cable adds significant cost to downhole data acquisition. In this paper, a proof of concept demonstration of an untethered sensor platform for logging vertical wells is presented. The platform is the size of a golf ball and works based on buoyancy change. The buoyant sensor housing and electronics initially holds a weight such that it sinks in the well. It releases the weight when it reaches a programmed depth and floats back up to the surface, logging data during the whole operation. The data are downloaded after retrieving the sensor. This miniaturized, tetherless platform can reduce the cost of logging operations and pave the way for semipermanent downhole sensors. [ABSTRACT FROM PUBLISHER]

Direct resistive sensor interface to a microcontroller has several advantages but has one prominent disadvantage, namely, the measurement is affected by the resistances of: 1) wires that connect the sensor to the port pins and 2) the internal resistances of the port pins of the microcontroller. A direct sensor-to-microcontroller interface scheme that compensates the effect due not only to resistances of lead wires but also the effect of microcontroller port pin’s internal resistance and any offset present in those pins is presented in this paper. Since the resistances of lead wires are compensated, automatic temperature compensation (temperature effect of lead wires) is also obtained. Simulation study and results obtained from a prototype built and tested establish the efficacy of the proposed method. A maximum error of 0.06% was observed from the prototype developed, when it was tested under room temperature, after interfacing it with the sensor Pt100, with a lead wire resistance R\mathrm {LD} = 21~\Omega . The error increased to a maximum of 0.08%, when the R\mathrm {LD} varied from 0 to $100~\Omega $ . When the same prototype was tested under elevated room temperature of 30 °C to 100 °C, the maximum error observed was 0.18%. [ABSTRACT FROM PUBLISHER]

This paper investigates the autocalibration of microelectromechanical systems (MEMS) triaxial accelerometer (TA) based on experimental design (DoE). First, for a special 6-parameter second-degree model, a six-point experimental scheme is proposed, and its G-optimality has been proven based on optimal DoE. Then, a new linearization approach is introduced, by which the TA model for autocalibration can be simplified as the expected second-degree form so that the proposed optimal experimental scheme can be applied. To reliably estimate the model parameter, a convergence-guaranteed iterative algorithm is also proposed, which can significantly reduce the bias caused by linearization. Thereafter, the effectiveness and robustness of the proposed approach have been demonstrated by simulation. Finally, the proposed calibration method has been experimentally verified using two typical types of MEMS TA, and desired experimental results effectively demonstrate the efficiency and accuracy of the proposed calibration approach. [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]

Moisture measurement in ppm level is always challenging and costly. Among different technologies available for moisture measurement, the thin film capacitive sensor-based dew point meter offers a low-cost solution. Still, the cost of the dew point meter is high and it suffers from high response time. There is a need of wireless moisture measurement in ppm level that is not available with the commercial meter according to our knowledge. This paper deals with development of a low-cost passive wireless tag for capacitive type sensors. The tag can be energized by any 13.56-MHz commercial tag reader from a distance of 1 cm (approx). The tag is capable of transmitting sensor data at 2.4-GHz ISM band up to a distance of 12 m. An efficient algorithm has been developed to reduce the power consumption. The prototype system has been tested with two custom designed capacitive sensors to measure humidity over a wide range. Both sensors, having a highly stable hygroscopic film of Al2O3, are fabricated in the lab. Finally, a low-cost (approximately U.S. $250) digital hygrometer to measure trace moisture has been developed. The performances of the digital hygrometer have been compared with the commercial dew point meter, and accuracy is found to be nearly 1% in the range of 6.5–127-ppm moisture. The system can be employed for contactless measurement with any capacitive sensor in the range of 50–3200 pF. [ABSTRACT FROM PUBLISHER]

Vortex flowmeter is installed in piping to measure the fluid flow rate. The piping is easily disturbed by strong transient impact in the application fields, such as other components impacting on the pipeline, manual knocking on the pipe, and opening and closing of valves. The strong transient impact will be picked up by the vortex flow sensor, which makes the vortex flowmeter output wrong measurement results. The current commonly used digital signal processing method can do nothing about it. To solve this problem, an experimental setup is built in our laboratory to study the impact interference, and a large number of vortex flow sensor output signals are collected. The characteristics of transient impacts outputted by the vortex sensor are analyzed so as to describe this type of signal quantitatively. The pattern of transient impact is that the signal amplitudes increase suddenly and then attenuate gradually. A segmented Kalman filter based digital signal processing method is proposed according to this pattern. The data segment containing strong transient impact is found first; the transient impact power is reduced by filtering the data segment second; and through spectral analysis of the filtered signal, the maximum peak of the spectrum is extracted as the vortex flow signal finally. The algorithm is implemented in real time by a low-power microcontroller. Both gas and water flow experiments have been conducted to verify the validity and reliability of the antistrong transient impact algorithm. [ABSTRACT FROM PUBLISHER]

This paper deals with the development of a signal conditioning circuit, with microcontroller compatibility, for interfacing capacitive sensors suitable for a wide range of applications. The circuit comprises of a capacitive active bridge, along with a relaxation oscillator for converting capacitance changes into frequency directly. The design, analysis, and experimental results of the circuit and its application to a thin-film-based humidity sensor and a capacitive transducer for measurement of the dielectric constant of edible oil are reported. The experimental results confirm the theoretical values predicted. The frequency output of the circuit has been used to determine the response characteristics of the trace moisture sensor and the dielectric constants of the edible oils. Finally, the output frequency has been calibrated in terms of the trace moisture in parts per million (ppm), using commercial dew point meter (SHAW, U.K.). The accuracy of moisture measurement using custom designed capacitive sensor for the full-scale moisture range of 4–100 ppm, compared with the dew point meter (accuracy ±0.1%), is found to be nearly ±1% and the resolution is 1 ppm moisture. The circuit is less complex and is easy to integrate to application-specific integrated circuits in a standard CMOS technology with high sensitivity (selectable). It can be easily reproduced with the cheapest possible components, while achieving fairly good performance in terms of both accuracy and dynamic range. [ABSTRACT FROM PUBLISHER]

This paper proposes an innovative method for power consumption measurement in microcontroller-based systems that provides high accuracy on a wide dynamic range of current values, which makes it particularly suitable for all those applications characterized by alternating low-/high-power modes and fast current variations. We demonstrate that using an op-amp-based voltage feedback configuration, it is possible to use shunt resistor values higher than usual to obtain increased voltage drops without affecting the microcontroller’s power supply voltage. Consequently, it is possible to directly use a data acquisition board to acquire the shunt voltage, eliminating all those common errors, like offset and gain, due to the use of an additional intermediate amplification stage. The proposed scheme has been successfully used to accurately characterize the power consumption of a single sensor node of a wireless sensor network. [ABSTRACT FROM AUTHOR]

This paper presents a new electronic Vernier fringe counter for the wavelength measurement of a diode laser in a scanning interferometer. The system is intended to be a low cost alternative to commercial systems used for gauge block calibration. The counter stage and phase coincidence detector are made with a microcontroller and high-speed CMOS logic to achieve the required resolution. The microcontroller also can synchronize with other elements to make a fully automated measurement system. This electronic design improves the resolution of the electronic counters in the previous designs. [ABSTRACT FROM AUTHOR]

This paper analyzes the energy consumption of direct interface circuits where the data conversion of a resistive sensor is performed by a direct connection to a set of digital ports of a microcontroller ( \mu \textC ). The causes of energy consumption as well as their relation to the measurement specifications in terms of uncertainty are analyzed. This analysis yields a tradeoff between energy consumption and measurement uncertainty, which sets a design procedure focused on achieving the lowest energy consumption for a given uncertainty and a measuring range. Together with this analysis, a novel experimental setup is proposed that allows one to measure the \mu \textC ’s timer quantization uncertainty. An application example is shown where the design procedure is applied. The experimental results fairly fit the theoretical analysis, yielding only 5~\mu \textJ to achieve nine effective number of bits (ENOB) in a measuring range from 1 to 1.38 \textk\Omega . With the same ENOB, the energy is reduced to 1.9~\mu \textJ when the measurement limits are changed to 100 and 138 \textk\Omega . [ABSTRACT FROM AUTHOR]

A simple signal conditioning circuit using a transformer ratio arm (TRA) bridge for converting capacitance change into frequency for capacitive sensors is presented. The circuit employs a relaxation oscillator in which the output frequency is linearly related to the capacitive unbalance of a TRA bridge. The design, analysis, and experimental results of the circuit and its application to a thin-film-based humidity sensor are reported. The experimental results confirm the theoretical value predicted. The circuit which offers the minimum parasitic earth capacitance effect has the potential for accurately monitoring measurement parameters, particularly ppm-level humidity. The simulation results for the effect of parasitic earth capacitances and ambient temperature on the output frequency have also been discussed. The pulse wave output of the circuit is interfaced with microcontroller for direct moisture display in ppm. The frequency sensitivity and nonlinearity of the sensor for the 0–110-ppm moisture range are found to be 10.94 Hz/ppm and 1.2%, respectively. [ABSTRACT FROM PUBLISHER]

A quasi-digital dc current sensor with rated current of ±600 A while overload current of about ±750 A is proposed in this paper. The new sensor is based on the open-loop self-oscillating fluxgate technology, but its originality is using a microcontroller unit to detect the duty cycle of the exciting voltage of the fluxgate. Compared with the published similar method, the whole signal chain of the new sensor is quasi-digital and without low-pass filter and analog-to-digital converter required when connected to digital systems. A precisely theoretical equation with respect to the linear dependence between the duty cycle and the current to be measured is established. Based on the equation, factors affecting the sensor sensitivity, accuracy, and resolution are determined, which constitutes the theoretical basis on the optimization design of the new sensor. The sensor linearity is improved using the least-squares polynomial fitting method. Some key specifications including the linearity, repeatability, and power supply effect of the sensor are characterized. The measurement results show that the linearity of the new sensor with the theoretical equation is better than 1.7% in the full scale of ±600 A, and can be improved to 0.3% when the fifth-order polynomial fitting method is used. [ABSTRACT FROM PUBLISHER]

This paper describes an eight-channel differential pulse generator based on a fast differential bipolar transistor output stage. It has been designed specifically to test new multichannel time-correlated single-photon counting (TCSPC) instruments, while maintaining a wide range of regulation possibilities in terms of frequency, amplitude, delay, and duty cycle. The input signal for each channel can be provided either by an on-board programmable frequency synthesizer or by an external reference shared by all channels. The chosen input is delivered to a delayer loop controlled by a field programmable gate array (FPGA), which provides the desired delay, minimizing the jitter contribution. The delayed signal is fed to an analog differential stage that provides the fast output, whose amplitude and offset are adjusted by a digital-to-analog converter, controlled by the FPGA. The experimental results on the instrument show an output slew rate of 1600 V/ \mu \texts over the complete full-scale range, which is between −2 and 6 V. The feedback delayer regulates the delay between 0 ns and 30 \mu \texts whereas the high time is adjustable from a minimum of 10 ns to a maximum of 30 \mu \texts . Finally, the frequency range is from 2 kHz to 50 MHz. All these adjustable parameters are managed by a microcontroller that works as an interface between the FPGAs and dedicated PC software. The implemented structure allows the system to achieve a time resolution down to 6 ps across all channels, making this instrument perfect for testing high time resolution TCSPC systems. [ABSTRACT FROM PUBLISHER]

We present a novel method for demodulating multiple frequency components of an ac magnetic field for use in electromagnetic tracking systems. Our undersampling method allows for a low sampling rate to acquire signals of interest in a range of 20–30 kHz without significant loss of precision. Lower sample rates give additional computation time between each sample, allowing for real-time demodulation without expensive high speed data acquisition and processing hardware. This also allows the use of low speed high precision analog-to-digital converters (ADCs) for sampling high frequency signals. The presented system demodulates 16 frequency components from two signals using an Arduino Due microcontroller and a two channel 16-bit ADC. The demodulated signals are then used to accurately determine the position of a magnetic sensor to within 1 mm in a volume 25 cm \times 25~cm \times 25 cm. The system accuracy compares well with both commercial and research systems in terms of accuracy, but at a dramatically lower cost. [ABSTRACT FROM PUBLISHER]

A challenging issue in photovoltaic (PV) systems is the performance monitoring of the PV panels. This is useful to detect the causes that might lower the energy production. In this paper, a novel technique for the transmission of the data obtained by a real time monitoring of a PV system is proposed. The PV panel's voltage, current, and temperature are measured by means of a low-cost smart monitoring and communications module and transferred to the central control system using power lines carriers communications technology on already existing dc power lines, which avoid additional installations costs. Simulations and experimental results together with an estimation of the measurement uncertainty are presented in order to validate the proposed idea. [ABSTRACT FROM PUBLISHER]

This present paper describes the development of a capacitance measurement system in the picofarad region. The system uses an universal serial bus port-based arrangement in conjunction with an indigenously developed Programmable Intelligent Computer microcontroller-based frequency synthesizer-vector voltmeter that can be used to measure the voltage in vector form and the capacitance can be determined using circuit solution technique. An intelligent two-layered, hierarchical reinforcement-based instrumentation scheme is proposed that can be integrated along with the original measurements to significantly improve the system performance. In layer 1, an extreme learning machine-based supervised phase reinforcement scheme is employed to improve the accuracy of the voltage measurement. Subsequently, in layer 2, local polynomial-based reinforcements are employed to improve both the resistive and reactive part measurements in the unknown capacitance. Three variants of ELM-based reinforcements are implemented for capacitance measurements in the range 100–10 000 pF and the utility of the hybrid ELM-polynomial-based reinforcements for such measurements is aptly demonstrated. [ABSTRACT FROM PUBLISHER]

Vortex flowmeter is apt to be disturbed by pipe vibration in industrial applications. It is a very difficult problem to be solved, and affects the applications of vortex flowmeter. To solve this key problem, the frequency features of the flow signal and vibration noise are analyzed. A frequency-variance algorithm is proposed to deal with the vortex flow sensor output signal. A variance threshold is set to distinguish the vortex flow signal from the vibration noise interference. A signal processing system based on an ultralow-power microcontroller is developed to implement the algorithm and to extract the flow rate information from the signal containing strong vibration noise. At the same time, this system meets the requirements of low-power and two-wire mode, and can be used in process control. The strong vibration experiments are conducted to validate the effectiveness of both antistrong vibration algorithm and the system. Only one vortex flow sensor is required in the vortex flowmeter, which avoids the design and installation of the vibration sensor and saves the costs of meter. [ABSTRACT FROM PUBLISHER]

Fast speed measurement and control signals are required for feedback control applications. In the proposed technique, a rotating magnetic field (RMF) is used to measure the speed and the variation in speed with high accuracy. In addition to a 400 Hz, three-phase input voltage circuit and an output zero-crossing detector circuit, a contact-type synchro is used as a primary transducer. A balanced three-phase ac voltage is applied to the stator windings of synchro, which produces an RMF. The frequency of electromotive force induced in the rotor circuit of synchro depends upon the speed of rotor or rotating member. The RMF revolves at a speed of 24 000 r/min, which is purposely kept very high in comparison with the speed of the rotor or rotating member. Thus, the measurement becomes very fast and the change in speed is sensed within 2.5 ms. The time response of the proposed scheme is also compared with the time response of a dc tachogenerator. A digital storage oscilloscope and a microcontroller are used for measurement of the output. The 16-b digital output of the microcontroller is made available as a feedback signal for control applications. The high accuracy of measurement of the proposed technique is also successfully used for calibration of different contact- and noncontact-type tachometers. [ABSTRACT FROM PUBLISHER]

Measuring solar irradiance allows for direct maximization of the efficiency in photovoltaic power plants. However, devices for solar irradiance sensing, such as pyranometers and pyrheliometers, are expensive and difficult to calibrate and thus seldom utilized in photovoltaic power plants. Indirect methods are instead implemented in order to maximize efficiency. This paper proposes a novel approach for solar irradiance measurement based on neural networks, which may, in turn, be used to maximize efficiency directly. An initial estimate suggests the cost of the sensor proposed herein may be price competitive with other inexpensive solutions available in the market, making the device a good candidate for large deployment in photovoltaic power plants. The proposed sensor is implemented through a photovoltaic cell, a temperature sensor, and a low-cost microcontroller. The use of a microcontroller allows for easy calibration, updates, and enhancement by simply adding code libraries. Furthermore, it can be interfaced via standard communication means with other control devices, integrated into control schemes, and remote-controlled through its embedded web server. The proposed approach is validated through experimental prototyping and compared against a commercial device. [ABSTRACT FROM PUBLISHER]

An automated irrigation system was developed to optimize water use for agricultural crops. The system has a distributed wireless network of soil-moisture and temperature sensors placed in the root zone of the plants. In addition, a gateway unit handles sensor information, triggers actuators, and transmits data to a web application. An algorithm was developed with threshold values of temperature and soil moisture that was programmed into a microcontroller-based gateway to control water quantity. The system was powered by photovoltaic panels and had a duplex communication link based on a cellular-Internet interface that allowed for data inspection and irrigation scheduling to be programmed through a web page. The automated system was tested in a sage crop field for 136 days and water savings of up to 90% compared with traditional irrigation practices of the agricultural zone were achieved. Three replicas of the automated system have been used successfully in other places for 18 months. Because of its energy autonomy and low cost, the system has the potential to be useful in water limited geographically isolated areas. [ABSTRACT FROM PUBLISHER]

A new approach for self-testing of analog parts terminated by analog-to-digital converters in mixed-signal electronic microsystems controlled by microcontrollers is presented. It is based upon a new fault diagnosis method using a transformation of the set of voltage samples of the time response of a tested analog part to a square impulse into localization curves placed in a multidimensional measurement space. The method can be used for fault detection and single soft fault localization. Modified digital Fourier transform formulas are used for conversion of the measurement results to the form used by the fault detection and localization algorithm during the self-testing of the system and also for creation of the fault dictionary. In this paper, the results of experimental verification of the approach are included. [ABSTRACT FROM PUBLISHER]

We have developed a binary compensation unit for balancing measurement bridges with cryogenic current comparators (CCCs) commonly used in resistance metrology. We present the basic design ideas for the new microcontroller-operated module. It offers balance over a gapless range of resistance ratios of the resistors to be compared. The binary setup allows for convenient calibration when being combined with a binary CCC. The calibration can be performed using the CCC's control electronics and software. Examples of measurements demonstrate the unit's high flexibility and stability of resistance calibration well below one part in 10^9 over a period of 21 hours. [ABSTRACT FROM PUBLISHER]

The aim of this paper consists in identifying the main design specifications of a portable analyzer that allows the vocal signal of a person under monitoring to be acquired and stored. Suitable calibration procedures will be also defined for the microphone used in the portable device in order to ensure the traceability of the obtained measurements. The collected data will be used to identify voice disorders, to prevent an improper use of the voice, and to evaluate the vocal effort induced by noisy and/or reverberant environments. The vocal analyzer is based on a contact microphone worn by the person under monitoring and a portable microcontroller-based unit that hosts the conditioning circuitry, analog-to-digital converter, and storing memory. Two alternative sensors are investigated as contact microphones: an accelerometer and an electret condenser microphone. The former is expected to exhibit a negligible sensitivity to airborne effects, and the latter would provide a larger bandwidth, thus allowing parameters related to the vowel quality to be estimated. Particular attention will be paid toward traceability assurance and uncertainty estimation, and a calibration procedure for each of the estimated parameters will be proposed. In this paper, a data-acquisition-board-based setup has been used instead of a portable microcontroller unit in order to easily perform tests that allow the used microphones to be characterized and the calibration procedures for the parameters of interest to be assessed. Experimental results are reported that refer to the estimation of the parameters sound pressure level (SPL) and fundamental frequency (F0). [ABSTRACT FROM AUTHOR]

This paper analyzes theoretically and experimentally the current consumption in direct interface circuits, i.e., circuits in which the sensor is directly connected to a microcontroller ( \mu\C) without using either a signal conditioning circuit or an analog-to-digital converter. The theoretical analysis, which takes into account the current consumed by both the internal electronics of the \mu\C and the external components, proposes formulas to estimate the average current consumption in active mode. The estimated values fairly agree with those obtained in the experimental tests carried out by an AVR ATtiny2313 \mu\C at different operating conditions. For example, the current consumption in active mode at 3 V–4 MHz was about 1.5 mA for the measurement of a 1-\k\Omega resistive sensor and 0.6 mA for the measurement of a 177-pF capacitive sensor. The results reported herein are expected to be useful for the design of direct interface circuits intended for battery-powered measurement systems. [ABSTRACT FROM PUBLISHER]

The use of biomimetic measurement systems as electronic tongues and noses has considerably increased in the last years. This paper presents the design of a low-cost electronic tongue system that includes a software application that runs on a personal computer and electronic equipment based on a 16-b microcontroller. The designed system is able to implement voltammetry and impedance spectroscopy measurements with different-electrode configurations. The data obtained from the electrochemical measurements can be used to build statistical models able to assess physicochemical properties of the samples. The designed system has been applied to the detection and quantification of trinitrotoluene (TNT), which is one of the most common explosive materials. Pulse voltammetry measurements were carried out on TNT samples with different concentration levels. The principal component analysis of the obtained results shows that the electronic tongue is able to detect TNT in acetonitrile samples. Prediction models were built with partial least squares regression, and a good correlation was observed between the pulse voltammetry measurements and the TNT concentration levels. In this experience, a new voltammetric data compression algorithm based on polynomial approximations has been tested with good results. The electronic tongue has also been applied to the prediction of water quality parameters in wastewater and to the evaluation of different-pulse array designs for pulse voltammetry experiences. [ABSTRACT FROM PUBLISHER]

An ultrasonic distance measurement system for use in air is presented. The measurement is based upon the two-frequency continuous-wave (TFCW) phase-shift method. In the system, two vernier caliper phase meters are used to measure the phase-shift data. The phase meter circuit developed to emulate the vernier caliper to measure the phase shift is able to eliminate the measuring error and produce higher resolution results without increasing the clock frequency. A single-chip microprocessor is used to control the TFCW phase-shift measurement and send the data to a personal computer for distance calibration and examination. The experimental results show that the accuracy of the system is \pm0.1362 mm and the distance resolution is 0.04% of the wavelength corresponding to the 40-kHz ultrasonic wave at a range of 50–200 mm. Therefore, the main advantages of this system are high resolution, high accuracy, low cost, and ease of implementation. [ABSTRACT FROM PUBLISHER]

Measurement errors such as gain, offset, nonlinearity, hysteresis, and cross-sensitivity degrade sensor performance, meaning that self-compensation becomes an important aspect in the maintenance of smart sensors. The progressive polynomial calibration (PPC) method is a step-by-step compensation algorithm that can fix some of the aforementioned errors by using microprocessors. In this paper, a modified-PPC (M-PPC) method is introduced. It is then shown that the number of calibration points, their selection, and permutation mechanisms can affect the M-PPC method. Therefore, an intelligent algorithm is presented to select appropriate calibration points from the input–output data. Intelligent selection of calibration points during the M-PPC method makes the calibration process simple, accurate, less time consuming, and low on computational load. A numerical example is provided to show the advantages of the proposed method in comparison with previously published ones. Finally, a test bench based on a thermistor with a nonlinearity characteristic is employed to examine the experimental results of the proposed method. [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 reports on the fabrication of a capacitive-type relative humidity (RH) sensor using screen printing processes for electrode film deposition. The applied measurement method based on microcontrollers is also reported. In this specific case, the microcontroller is used to measure RH by means of a capacitive sensor with a simple low-cost electronic system. In addition, a comparison between two different types of polyester substrates [Melinex (DuPont) and CG3460 (3M)] is shown. Both polyester substrates have similar properties, and only the thickness is different (175 \mu\m for Melinex and 100 \mu\m for CG3460). A nonlineal response has been obtained in this type of sensors. In order to linearize the response and reduce the external hardware, an artificial neural network embedded into the microcontroller has been used. [ABSTRACT FROM PUBLISHER]

A high-precision ultrasonic ranging system platform is presented and evaluated in this work. By queuing peaks of the self-destructive interference, the proposed hardware platform can enhance the accuracy without complex algorithms. At the emitter, the developed technique generates two amplitude-modulated pulses with 180 ^\circ phase shift. At the receiver, on the other hand, the two pulses create a self-destructive interference. This interference waveform can be used to directly determine the time of flight. By implementing the developed technique on a low-cost microcontroller platform, the experimental result shows the accuracy with 0.06 mm over a range of 50–1000 mm. Moreover, the system accuracy remains 0.15 mm within the range of 2000 mm. The developed system establishes an effective method for low-cost and high-performance ranging systems. [ABSTRACT FROM AUTHOR]

This paper presents the development of an intelligent fuzzy-based compensation scheme, utilizing reinforcement learning methodology, which can be used to compensate the reading of an unknown voltage, in vector form. This compensator is implemented online, in real time, with an indigenously developed microcontroller-based scheme that can be used both as a frequency synthesizer and as a vector voltmeter. This frequency synthesizer/vector voltmeter is developed using a direct digital synthesis method for the frequency synthesizer and a synchronous detection technique for the vector voltmeter. The developed fuzzy compensator has been tested in both offline and online modes, and in both cases, it has been found to significantly improve the accuracy of the measurement compared to those obtained with an uncompensated vector voltmeter. It has been shown that the final compensated measurements are in close agreement with the true unknown voltages under measurement. [ABSTRACT FROM AUTHOR]

An optical scanner, also known as a flux mapping system, capable of acquiring a flux distribution pattern of a light source on a 2-D flat surface, has been designed and constructed. The novel optical scanner can measure the light flux distribution at high resolution with fewer sensors in a relatively short amount of time, and it can be used for precise calibration of any light source. The design of the optical scanner consisted of a single row of photodiodes with fixed distances that can scan and acquire flux distribution data in the 2-D measurement plane. In our prototype design of the novel optical scanner, 25 photodiodes with a photosensitive area of 1 \cm^2 each were arranged in a single row and fixed to an aluminum holder. The resulting scanner was fast enough to perform scanning and recording of light irradiance over a test plane area of 1125 \cm^2 within a period of 5 s. [ABSTRACT FROM PUBLISHER]

This paper presents a small microcontroller-based sine-wave generator for probe signals of a wide range of amplitudes and frequencies, which requires very little energy so that it can be used for wireless applications in biosensing. The presented realization generates a 10-kHz sine wave with a 100-mV peak-to-peak voltage. Its total harmonic distortion is less than 0.15%, and the spurious free dynamic range excluding harmonics is about 85 dB. The generator's total power consumption at a 3.3-V supply voltage and without output buffers is less than 3.5 mW. This value includes the power requirement of the microcontroller's internal 8-MHz clock generator and is below the power needs of current direct-digital-synthesis-based signal generators. The presented concept bases on commercially available electronic components and is implemented for probe signal generation in wireless batteryless tags for long-term impedance measurements on standard microbiological cell cultures. The included microcontroller enables the use of a phase-controlled trigger signal and other simultaneous control functions, e.g., for peripheral components and data communication. [ABSTRACT FROM AUTHOR]