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A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Physical Sensors".

Deadline for manuscript submissions: closed (31 March 2017) | Viewed by 45320

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Special Issue Editors

Dr. Manel Gasulla Forner

E-Mail Website
Guest Editor

e-CAT Reaserch Group, Department of Electronic Engineering, Castelldefels School of Telecommunications and Aerospace Engineering, Universitat Politècnica de Catalunya, c/Esteve Terradas, 7, 08860 Castelldefels (Barcelona), Spain
Interests: smart sensors; direct sensor-to-microcontroller electronic interfaces; energy harvesting and wireless power transfer for autonomous sensors

Dr. Ferran Reverter

E-Mail Website
Guest Editor

Universitat Politècnica de Catalunya
Interests: sensor electronics; smart sensors; temperature sensors; on-chip thermal testing; power processing circuits; DC/DC converters

Special Issue Information

Dear Colleagues,

Sensors are present in many electronic products and systems and are essential for gathering relevant information of physical and chemical quantities. Their importance is growing with increasing use in smart phones and other mobile devices, such as smart watches and health- and sport-related gadgets. In these products, as the power supply comes from a battery, a low-power consumption is a must. Sensors are also the core of wireless sensor networks and the Internet-of-Things, which are employed, for instance, in smart cities and buildings, where energy harvesting is a very attractive solution for power supply.

Autonomous Sensors are referred here as electronic sensors and their electronic interfaces that can operate autonomously and wirelessly during a relatively long period of time from an embedded local power source, which can be either a battery or an energy harvester. Further, the autonomous sensor is expected to be of low cost and small size. This Special Issue invites reviews and original papers dealing with relevant aspects of Autonomous Sensors, mainly focused on (a) improving the accuracy/resolution of the measurement for a given power consumption, and (b) increasing their operation time or allowing a “perpetual” operation. Average consumption of the autonomous sensor is expected in the sub-watt range. Thus, relevant topics are the reduction of the power consumption of the electronic sensors and their interfaces, and the increase of the power efficiency of the power management section. In case that energy harvesting is proposed, techniques for maximizing the harvested power are relevant. Papers that focus on specific applications or deal with all or most of the blocks of an autonomous sensor are also welcome.

Dr. Manuel Gasulla
Dr. Ferran Reverter
Guest Editors

Manuscript Submission Information

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Keywords

Low-power smart sensors
Low-power sensor electronic interfaces
Microcontroller-based readout circuits
Low-power management
Energy harvesting
Maximum power point tracking

Published Papers (6 papers)

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Research

3090 KiB

Open AccessArticle

Analysis of the Optimum Gain of a High-Pass L-Matching Network for Rectennas

by Manel Gasulla, Josep Jordana, Francesc-Josep Robert and Jordi Berenguer

Sensors 2017, 17(8), 1712; https://doi.org/10.3390/s17081712 - 25 Jul 2017

Cited by 4 | Viewed by 4530

Abstract

Rectennas, which mainly consist of an antenna, matching network, and rectifier, are used to harvest radiofrequency energy in order to power tiny sensor nodes, e.g., the nodes of the Internet of Things. This paper demonstrates for the first time, the existence of an optimum voltage gain for high-pass L-matching networks used in rectennas by deriving an analytical expression. The optimum gain is that which leads to maximum power efficiency of the rectenna. Here, apart from the L-matching network, a Schottky single-diode rectifier was used for the rectenna, which was optimized at 868 MHz for a power range from −30 dBm to −10 dBm. As the theoretical expression depends on parameters not very well-known a priori, an accurate search of the optimum gain for each power level was performed via simulations. Experimental results show remarkable power efficiencies ranging from 16% at −30 dBm to 55% at −10 dBm, which are for almost all the tested power levels the highest published in the literature for similar designs. Full article

(This article belongs to the Special Issue Autonomous Sensors)

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3876 KiB

Open AccessArticle

Measuring Dynamic Signals with Direct Sensor-to-Microcontroller Interfaces Applied to a Magnetoresistive Sensor

by Ernesto Sifuentes, Rafael Gonzalez-Landaeta, Juan Cota-Ruiz and Ferran Reverter

Sensors 2017, 17(5), 1150; https://doi.org/10.3390/s17051150 - 18 May 2017

Cited by 13 | Viewed by 6135

Abstract

This paper evaluates the performance of direct interface circuits (DIC), where the sensor is directly connected to a microcontroller, when a resistive sensor subjected to dynamic changes is measured. The theoretical analysis provides guidelines for the selection of the components taking into account both the desired resolution and the bandwidth of the input signal. Such an analysis reveals that there is a trade-off between the sampling frequency and the resolution of the measurement, and this depends on the selected value of the capacitor that forms the RC circuit together with the sensor resistance. This performance is then experimentally proved with a DIC measuring a magnetoresistive sensor exposed to a magnetic field of different frequencies, amplitudes, and waveforms. A sinusoidal magnetic field up to 1 kHz can be monitored with a resolution of eight bits and a sampling frequency of around 10 kSa/s. If a higher resolution is desired, the sampling frequency has to be lower, thus limiting the bandwidth of the dynamic signal under measurement. The DIC is also applied to measure an electrocardiogram-type signal and its QRS complex is well identified, which enables the estimation, for instance, of the heart rate. Full article

(This article belongs to the Special Issue Autonomous Sensors)

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3096 KiB

Open AccessArticle

A Self-Powered and Autonomous Fringing Field Capacitive Sensor Integrated into a Micro Sprinkler Spinner to Measure Soil Water Content

by Eduardo Ferreira Da Costa, Nestor E. De Oliveira, Flávio J. O. Morais, Pedro Carvalhaes-Dias, Luis Fernando C. Duarte, Andreu Cabot and J. A. Siqueira Dias

Sensors 2017, 17(3), 575; https://doi.org/10.3390/s17030575 - 12 Mar 2017

Cited by 36 | Viewed by 7242

Abstract

We present here the design and fabrication of a self-powered and autonomous fringing field capacitive sensor to measure soil water content. The sensor is manufactured using a conventional printed circuit board and includes a porous ceramic. To read the sensor, we use a circuit that includes a 10 kHz triangle wave generator, an AC amplifier, a precision rectifier and a microcontroller. In terms of performance, the sensor’s capacitance (measured in a laboratory prototype) increases up to 5% when the volumetric water content of the porous ceramic changed from 3% to 36%, resulting in a sensitivity of

S = 15.5

pF per unity change. Repeatability tests for capacitance measurement showed that the

θ_{v}

sensor’s root mean square error is 0.13%. The average current consumption of the system (sensor and signal conditioning circuit) is less than 1.5

μ

A, which demonstrates its suitability for being powered by energy harvesting systems. We developed a complete irrigation control system that integrates the sensor, an energy harvesting module composed of a microgenerator installed on the top of a micro sprinkler spinner, and a DC/DC converter circuit that charges a 1 F supercapacitor. The energy harvesting module operates only when the micro sprinkler spinner is irrigating the soil, and the supercapacitor is fully charged to 5 V in about 3 h during the first irrigation. After the first irrigation, with the supercap fully charged, the system can operate powered only by the supercapacitor for approximately 23 days, without any energy being harvested. Full article

(This article belongs to the Special Issue Autonomous Sensors)

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3765 KiB

Open AccessArticle

A Miniature Magnetic-Force-Based Three-Axis AC Magnetic Sensor with Piezoelectric/Vibrational Energy-Harvesting Functions

by Chiao-Fang Hung, Po-Chen Yeh and Tien-Kan Chung

Sensors 2017, 17(2), 308; https://doi.org/10.3390/s17020308 - 08 Feb 2017

Cited by 13 | Viewed by 7993

Abstract

In this paper, we demonstrate a miniature magnetic-force-based, three-axis, AC magnetic sensor with piezoelectric/vibrational energy-harvesting functions. For magnetic sensing, the sensor employs a magnetic–mechanical–piezoelectric configuration (which uses magnetic force and torque, a compact, single, mechanical mechanism, and the piezoelectric effect) to convert x-axis and y-axis in-plane and z-axis magnetic fields into piezoelectric voltage outputs. Under the x-axis magnetic field (sine-wave, 100 Hz, 0.2–3.2 gauss) and the z-axis magnetic field (sine-wave, 142 Hz, 0.2–3.2 gauss), the voltage output with the sensitivity of the sensor are 1.13–26.15 mV with 8.79 mV/gauss and 1.31–8.92 mV with 2.63 mV/gauss, respectively. In addition, through this configuration, the sensor can harness ambient vibrational energy, i.e., possessing piezoelectric/vibrational energy-harvesting functions. Under x-axis vibration (sine-wave, 100 Hz, 3.5 g) and z-axis vibration (sine-wave, 142 Hz, 3.8 g), the root-mean-square voltage output with power output of the sensor is 439 mV with 0.333 μW and 138 mV with 0.051 μW, respectively. These results show that the sensor, using this configuration, successfully achieves three-axis magnetic field sensing and three-axis vibration energy-harvesting. Due to these features, the three-axis AC magnetic sensor could be an important design reference in order to develop future three-axis AC magnetic sensors, which possess energy-harvesting functions, for practical industrial applications, such as intelligent vehicle/traffic monitoring, processes monitoring, security systems, and so on. Full article

(This article belongs to the Special Issue Autonomous Sensors)

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4279 KiB

Open AccessArticle

Real-Time Performance of a Self-Powered Environmental IoT Sensor Network System

by Fan Wu, Christoph Rüdiger and Mehmet Rasit Yuce

Sensors 2017, 17(2), 282; https://doi.org/10.3390/s17020282 - 01 Feb 2017

Cited by 102 | Viewed by 11104

Abstract

Wireless sensor networks (WSNs) play an increasingly important role in monitoring applications in many areas. With the emergence of the Internet-of-Things (IoT), many more lowpower sensors will need to be deployed in various environments to collect and monitor data about environmental factors in real time. Providing power supply to these sensor nodes becomes a critical challenge for realizations of IoT applications as sensor nodes are normally battery-powered and have a limited lifetime. This paper proposes a wireless sensor network that is powered by solar energy harvesting. The sensor network monitors the environmental data with low-power sensor electronics and forms a network using multiple XBee wireless modules. A detailed performance analysis of the network system under solar energy harvesting has been presented. The sensor network system and the proposed energy-harvesting techniques are configured to achieve a continuous energy source for the sensor network. The proposed energy-harvesting system has been successfully designed to enable an energy solution in order to keep sensor nodes active and reliable for a whole day. The paper also outlines some of our experiences in real-time implementation of a sensor network system with energy harvesting. Full article

(This article belongs to the Special Issue Autonomous Sensors)

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4910 KiB

Open AccessArticle

Atmospheric Measurements by Ultra-Light SpEctrometer (AMULSE) Dedicated to Vertical Profile in Situ Measurements of Carbon Dioxide (CO₂) Under Weather Balloons: Instrumental Development and Field Application

by Lilian Joly, Rabih Maamary, Thomas Decarpenterie, Julien Cousin, Nicolas Dumelié, Nicolas Chauvin, Dominique Legain, Diane Tzanos and Georges Durry

Sensors 2016, 16(10), 1609; https://doi.org/10.3390/s16101609 - 29 Sep 2016

Cited by 7 | Viewed by 6967

Abstract

The concentration of greenhouse gases in the atmosphere plays an important role in the radiative effects in the Earth’s climate system. Therefore, it is crucial to increase the number of atmospheric observations in order to quantify the natural sinks and emission sources. We report in this paper the development of a new compact lightweight spectrometer (1.8 kg) called AMULSE based on near infrared laser technology at 2.04 µm coupled to a 6-m open-path multipass cell. The measurements were made using the Wavelength Modulation Spectroscopy (WMS) technique and the spectrometer is hence dedicated to in situ measuring the vertical profiles of the CO₂ at high precision levels (σ_Allan = 0.96 ppm in 1 s integration time (1σ)) and with high temporal/spatial resolution (1 Hz/5 m) using meteorological balloons. The instrument is compact, robust, cost-effective, fully autonomous, has low-power consumption, a non-intrusive probe and is plug & play. It was first calibrated and validated in the laboratory and then used for 17 successful flights up to 10 km altitude in the region Champagne—Ardenne, France in 2014. A rate of 100% of instrument recovery was validated due to the pre-localization prediction of the Météo—France based on the flight simulation software. Full article

(This article belongs to the Special Issue Autonomous Sensors)

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