Sensors

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11 pages, 3392 KiB

Open AccessFeature PaperArticle

Development of a Sensor Node for Remote Monitoring of Plants

by Alexandro Catini, Leonardo Papale, Rosamaria Capuano, Valentina Pasqualetti, Davide Di Giuseppe, Stefano Brizzolara, Pietro Tonutti and Corrado Di Natale

Sensors 2019, 19(22), 4865; https://doi.org/10.3390/s19224865 - 08 Nov 2019

Cited by 21 | Viewed by 3515

Abstract

The appraisal of stress in plants is of great relevance in agriculture and any time the transport of living plants is involved. Wireless sensor networks (WSNs) are an optimal solution to simultaneously monitor a large number of plants in a mostly automatic way. [...] Read more.

The appraisal of stress in plants is of great relevance in agriculture and any time the transport of living plants is involved. Wireless sensor networks (WSNs) are an optimal solution to simultaneously monitor a large number of plants in a mostly automatic way. A number of sensors are readily available to monitor indicators that are likely related to stress. The most common of them include the levels of total volatile compounds and CO₂ together with common physical parameters such as temperature, relative humidity, and illumination, which are known to affect plants’ behavior. Recent progress in microsensors and communication technologies, such as the LoRa protocol, makes it possible to design sensor nodes of high sensitivity where power consumption, transmitting distances, and costs are optimized. In this paper, the design of a WSN dedicated to plant stress monitoring is described. The nodes have been tested on European privet (Ligustrum Jonandrum) kept in completely different conditions in order to induce opposite level of stress. The results confirmed the relationship between the release of total Volatile Organic Compounds (VOCs) and the environmental conditions. A machine learning model based on recursive neural networks demonstrates that total VOCs can be estimated from the measure of the environmental parameters. Full article

(This article belongs to the Special Issue Electronic Interfaces for Sensors)

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12 pages, 4496 KiB

Open AccessArticle

Experimental Assessment of the Interface Electronic System for PVDF-Based Piezoelectric Tactile Sensors

by Moustafa Saleh, Yahya Abbass, Ali Ibrahim and Maurizio Valle

Sensors 2019, 19(20), 4437; https://doi.org/10.3390/s19204437 - 14 Oct 2019

Cited by 12 | Viewed by 3463

Abstract

Tactile sensors are widely employed to enable the sense of touch for applications such as robotics and prosthetics. In addition to the selection of an appropriate sensing material, the performance of the tactile sensing system is conditioned by its interface electronic system. On [...] Read more.

Tactile sensors are widely employed to enable the sense of touch for applications such as robotics and prosthetics. In addition to the selection of an appropriate sensing material, the performance of the tactile sensing system is conditioned by its interface electronic system. On the other hand, due to the need to embed the tactile sensing system into a prosthetic device, strict requirements such as small size and low power consumption are imposed on the system design. This paper presents the experimental assessment and characterization of an interface electronic system for piezoelectric tactile sensors for prosthetic applications. The interface electronic is proposed as part of a wearable system intended to be integrated into an upper limb prosthetic device. The system is based on a low power arm-microcontroller and a DDC232 device. Electrical and electromechanical setups have been implemented to assess the response of the interface electronic with PVDF-based piezoelectric sensors. The results of electrical and electromechanical tests validate the correct functionality of the proposed system. Full article

(This article belongs to the Special Issue Electronic Interfaces for Sensors)

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17 pages, 1507 KiB

Open AccessArticle

An Amplifier-Less Acquisition Chain for Power Measurements in Series Resonant Inverters

by Jorge Villa, José I. Artigas, Luis A. Barragán and Denis Navarro

Sensors 2019, 19(19), 4343; https://doi.org/10.3390/s19194343 - 08 Oct 2019

Cited by 2 | Viewed by 2427

Abstract

Successive approximation register (SAR) analog-to-digital converter (ADC) manufacturers recommend the use of a driver amplifier to achieve the best performance. When a driver amplifier is not used, the conversion speed is severely penalized because of the need to meet the settling time constraint. [...] Read more.

Successive approximation register (SAR) analog-to-digital converter (ADC) manufacturers recommend the use of a driver amplifier to achieve the best performance. When a driver amplifier is not used, the conversion speed is severely penalized because of the need to meet the settling time constraint. This paper proposes a simple digital correction method to raise the performance (conversion speed and/or accuracy) when the acquisition chain lacks a driver amplifier. It is intended to reduce the cost, size and power consumption of the conditioning circuit while maintaining acceptable performance. The method is applied to the measurement of the output power delivered by a series resonant inverter for domestic induction heating. Full article

(This article belongs to the Special Issue Electronic Interfaces for Sensors)

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17 pages, 4148 KiB

Open AccessArticle

A VCO-Based CMOS Readout Circuit for Capacitive MEMS Microphones

by Andres Quintero, Fernando Cardes, Carlos Perez, Cesare Buffa, Andreas Wiesbauer and Luis Hernandez

Sensors 2019, 19(19), 4126; https://doi.org/10.3390/s19194126 - 24 Sep 2019

Cited by 14 | Viewed by 6898

Abstract

Microelectromechanical systems (MEMS) microphone sensors have significantly improved in the past years, while the readout electronic is mainly implemented using switched-capacitor technology. The development of new battery powered “always-on” applications increasingly requires a low power consumption. In this paper, we show a new [...] Read more.

Microelectromechanical systems (MEMS) microphone sensors have significantly improved in the past years, while the readout electronic is mainly implemented using switched-capacitor technology. The development of new battery powered “always-on” applications increasingly requires a low power consumption. In this paper, we show a new readout circuit approach which is based on a mostly digital Sigma Delta (

Σ Δ

) analog-to-digital converter (ADC). The operating principle of the readout circuit consists of coupling the MEMS sensor to an impedance converter that modulates the frequency of a stacked-ring oscillator—a new voltage-controlled oscillator (VCO) circuit featuring a good trade-off between phase noise and power consumption. The frequency coded signal is then sampled and converted into a noise-shaped digital sequence by a time-to-digital converter (TDC). A time-efficient design methodology has been used to optimize the sensitivity of the oscillator combined with the phase noise induced by

1 / f

and thermal noise. The circuit has been prototyped in a 130 nm CMOS process and directly bonded to a standard MEMS microphone. The proposed VCO-based analog-to-digital converter (VCO-ADC) has been characterized electrically and acoustically. The peak signal-to-noise and distortion ratio (SNDR) obtained from measurements is 77.9 dB-A and the dynamic range (DR) is 100 dB-A. The current consumption is 750

μ

A at 1.8 V and the effective area is 0.12 mm

^{2}

. This new readout circuit may represent an enabling advance for low-cost digital MEMS microphones. Full article

(This article belongs to the Special Issue Electronic Interfaces for Sensors)

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9 pages, 1882 KiB

Open AccessArticle

A Sensor Platform for Athletes’ Training Supervision: A Proof of Concept Study

by Alessandro Zompanti, Anna Sabatini, Marco Santonico, Simone Grasso, Antonio Gianfelici, Bruno Donatucci, Andrea Di Castro and Giorgio Pennazza

Sensors 2019, 19(18), 3948; https://doi.org/10.3390/s19183948 - 12 Sep 2019

Cited by 4 | Viewed by 2998

Abstract

One of the basic needs of professional athletes is the real-time and non-invasive monitoring of their activities. The use of these kind of data is necessary to develop strategies for specific tailored training in order to improve performances. The sensor system presented in [...] Read more.

One of the basic needs of professional athletes is the real-time and non-invasive monitoring of their activities. The use of these kind of data is necessary to develop strategies for specific tailored training in order to improve performances. The sensor system presented in this work has the aim to adopt a novel approach for the monitoring of physiological parameters, and athletes’ performances, during their training. The anaerobic threshold is herein identified with the monitoring of the lactate concentration and the respiratory parameters. The data collected by the sensor are used to build a model using a supervised method (based on the partial least squares method, PLS) to predict the values of the parameters of interest. The sensor is able to measure the lactate concentration from a sample of saliva and it can estimate a respiratory parameter, such as maximal oxygen consumption, maximal carbon dioxide production and respiratory rate from a sample of exhaled breath. The main advantages of the device are the low power; the wireless communication; and the non-invasive sampling method, which allow its use in a real context of sport practice. Full article

(This article belongs to the Special Issue Electronic Interfaces for Sensors)

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16 pages, 5705 KiB

Open AccessArticle

A VCII-Based Stray Insensitive Analog Interface for Differential Capacitance Sensors

by Gianluca Barile, Leila Safari, Giuseppe Ferri and Vincenzo Stornelli

Sensors 2019, 19(16), 3545; https://doi.org/10.3390/s19163545 - 14 Aug 2019

Cited by 25 | Viewed by 4002

Abstract

In this paper, a novel approach to implement a stray insensitive CMOS interface for differential capacitive sensors is presented. The proposed circuit employs, for the first time, second-generation voltage conveyors (VCIIs) and produces an output voltage proportional to differential capacitor changes. Using VCIIs [...] Read more.

In this paper, a novel approach to implement a stray insensitive CMOS interface for differential capacitive sensors is presented. The proposed circuit employs, for the first time, second-generation voltage conveyors (VCIIs) and produces an output voltage proportional to differential capacitor changes. Using VCIIs as active devices inherently allows the circuit to process the signal in the current domain, and hence, to benefit from its intrinsic advantages, such as high speed and simple implementation, while still being able to natively interface with voltage mode signal processing stages at necessity. The insensitiveness to the effects of parasitic capacitances is achieved through a simple feedback loop. In addition, the proposed circuit shows a very simple and switch-free structure (which can be used for both linear and hyperbolic sensors), improving its accuracy. The readout circuit was designed in a standard 0.35 μm CMOS technology under a supply voltage of ±1.65 V. Before the integrated circuit fabrication, to produce tangible proof of the effectiveness of the proposed architecture, a discrete version of the circuit was also prototyped using AD844 and LF411 to implement a discrete VCII. The achieved measurement results are in good agreement with theory and simulations, showing a constant sensitivity up to 412 mV/pF, a maximum linearity error of 1.9%FS, and acknowledging a good behavior with low baseline capacitive sensors (10 pF in the proposed measurements). A final table is also given to summarize the key specs of the proposed work comparing them to the available literature. Full article

(This article belongs to the Special Issue Electronic Interfaces for Sensors)

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14 pages, 3785 KiB

Open AccessArticle

Design of a RF Switch Used in Redundant Atomic Clock Configurations

by Yuqing Hou, Sangyuan Wang, Sheng Tang and Tao Zhang

Sensors 2019, 19(10), 2331; https://doi.org/10.3390/s19102331 - 20 May 2019

Viewed by 4001

Abstract

Atomic clocks provide frequency reference signals for communication, aerospace, satellite navigation and other systems. The redundant configuration of atomic clocks is necessary for ensuring the continuity and stability of the system. A radio frequency (RF) switch is usually used as a switching device [...] Read more.

Atomic clocks provide frequency reference signals for communication, aerospace, satellite navigation and other systems. The redundant configuration of atomic clocks is necessary for ensuring the continuity and stability of the system. A radio frequency (RF) switch is usually used as a switching device in the switching system of the host atomic clock and the backup atomic clock. When the atomic clock fails, the switching between the host and the backup clock can be carried out quickly. Aiming at the fast switching requirements of atomic clock RF signals, this paper proposes a new series-shunt Positive Intrinsic Negative (PIN) switch design. In this paper, the evaluation of the RF switches is conducted by using the metrics of switching speed, insertion loss, isolation, return loss at on state and return loss at off state. Experimental result shows that the new PIN switch has better and more comprehensive performance metrics than the electromechanical switch, FET switch and conventional PIN switch. In particular, the switching speed is 53 ns faster than the conventional series-shunt PIN switch. Full article

(This article belongs to the Special Issue Electronic Interfaces for Sensors)

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13 pages, 5742 KiB

Open AccessArticle

Dynamic pH Sensor with Embedded Calibration Scheme by Advanced CMOS FinFET Technology

by Chien-Ping Wang, Ying-Chun Shen, Peng-Chun Liou, Yu-Lun Chueh, Yue-Der Chih, Jonathan Chang, Chrong-Jung Lin and Ya-Chin King

Sensors 2019, 19(7), 1585; https://doi.org/10.3390/s19071585 - 02 Apr 2019

Cited by 5 | Viewed by 4248

Abstract

In this work, we present a novel pH sensor using efficient laterally coupled structure enabled by Complementary Metal-Oxide Semiconductor (CMOS) Fin Field-Effect Transistor (FinFET) processes. This new sensor features adjustable sensitivity, wide sensing range, multi-pad sensing capability and compatibility to advanced CMOS technologies. [...] Read more.

In this work, we present a novel pH sensor using efficient laterally coupled structure enabled by Complementary Metal-Oxide Semiconductor (CMOS) Fin Field-Effect Transistor (FinFET) processes. This new sensor features adjustable sensitivity, wide sensing range, multi-pad sensing capability and compatibility to advanced CMOS technologies. With a self-balanced readout scheme and proposed corresponding circuit, the proposed sensor is found to be easily embedded into integrated circuits (ICs) and expanded into sensors array. To ensure the robustness of this new device, the transient response and noise analysis are performed. In addition, an embedded calibration operation scheme is implemented to prevent the proposed sensing device from the background offset from process variation, providing reliable and stable sensing results. Full article

(This article belongs to the Special Issue Electronic Interfaces for Sensors)

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13 pages, 4338 KiB

Open AccessArticle

Deep Submicron EGFET Based on Transistor Association Technique for Chemical Sensing

by Salvatore A. Pullano, Nishat T. Tasneem, Ifana Mahbub, Samira Shamsir, Marta Greco, Syed K. Islam and Antonino S. Fiorillo

Sensors 2019, 19(5), 1063; https://doi.org/10.3390/s19051063 - 02 Mar 2019

Cited by 21 | Viewed by 5481

Abstract

Extended-gate field-effect transistor (EGFET) is an electronic interface originally developed as a substitute for an ion-sensitive field-effect transistor (ISFET). Although the literature shows that commercial off-the-shelf components are widely used for biosensor fabrication, studies on electronic interfaces are still scarce (e.g., noise processes, [...] Read more.

Extended-gate field-effect transistor (EGFET) is an electronic interface originally developed as a substitute for an ion-sensitive field-effect transistor (ISFET). Although the literature shows that commercial off-the-shelf components are widely used for biosensor fabrication, studies on electronic interfaces are still scarce (e.g., noise processes, scaling). Therefore, the incorporation of a custom EGFET can lead to biosensors with optimized performance. In this paper, the design and characterization of a transistor association (TA)-based EGFET was investigated. Prototypes were manufactured using a 130 nm standard complementary metal-oxide semiconductor (CMOS) process and compared with devices presented in recent literature. A DC equivalence with the counterpart involving a single equivalent transistor was observed. Experimental results showed a power consumption of 24.99 mW at 1.2 V supply voltage with a minimum die area of 0.685 × 1.2 mm². The higher aspect ratio devices required a proportionally increased die area and power consumption. Conversely, the input-referred noise showed an opposite trend with a minimum of 176.4 nV_rms over the 0.1 to 10 Hz frequency band for a higher aspect ratio. EGFET as a pH sensor presented further validation of the design with an average voltage sensitivity of 50.3 mV/pH, a maximum current sensitivity of 15.71 mA^1/2/pH, a linearity higher than 99.9%, and the possibility of operating at a lower noise level with a compact design and a low complexity. Full article

(This article belongs to the Special Issue Electronic Interfaces for Sensors)

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9 pages, 3813 KiB

Open AccessArticle

Fully Integrated Light-Sensing Stimulator Design for Subretinal Implants

by Hosung Kang, Wajahat H. Abbasi, Seong-Woo Kim and Jungsuk Kim

Sensors 2019, 19(3), 536; https://doi.org/10.3390/s19030536 - 28 Jan 2019

Cited by 15 | Viewed by 4072

Abstract

This paper presents a fully integrated photodiode-based low-power and low-mismatch stimulator for a subretinal prosthesis. It is known that a subretinal prosthesis achieves 1600-pixel stimulators on a limited single-chip area that is implanted beneath the bipolar cell layer. However, the high-density pixels cause [...] Read more.

This paper presents a fully integrated photodiode-based low-power and low-mismatch stimulator for a subretinal prosthesis. It is known that a subretinal prosthesis achieves 1600-pixel stimulators on a limited single-chip area that is implanted beneath the bipolar cell layer. However, the high-density pixels cause high power dissipation during stimulation and high fabrication costs because of special process technologies such as the complementary metal-oxide semiconductor CMOS image sensor process. In addition, the many residual charges arising from the high-density pixel stimulation have deleterious effects, such as tissue damage and electrode corrosion, on the retina tissue. In this work, we adopted a switched-capacitor current mirror technique for the single-pixel stimulator (SPStim) that enables low power consumption and low mismatch in the subretinal device. The customized P+/N-well photodiode used to sense the incident light in the SPStim also reduces the fabrication cost. The 64-pixel stimulators are fabricated in a standard 0.35-μm CMOS process along with a global digital controller, which occupies a chip area of 4.3 × 3.2 mm² and are ex-vivo demonstrated using a dissected pig eyeball. According to measured results, the SPStim accomplishes a maximum biphasic pulse amplitude of 143 μA, which dissipates an average power of 167 μW in a stimulation period of 5 ms, and an average mismatch of 1.12 % between the cathodic and anodic pulses. Full article

(This article belongs to the Special Issue Electronic Interfaces for Sensors)

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13 pages, 3847 KiB

Open AccessArticle

Low-Power Highly Robust Resistance-to-Period Converter

by Luis C. Álvarez-Simón, Emmanuel Gómez-Ramírez and María Teresa Sanz-Pascual

Sensors 2019, 19(1), 8; https://doi.org/10.3390/s19010008 - 20 Dec 2018

Cited by 4 | Viewed by 3276

Abstract

This paper presents a novel structure of Resistance- to-Period (R-T) Converter highly robust to supply and temperature variations. Robustness is achieved by using the ratiometric approach so that complex circuits or high accuracy voltage references are not necessary. To prove the proposed architecture [...] Read more.

This paper presents a novel structure of Resistance- to-Period (R-T) Converter highly robust to supply and temperature variations. Robustness is achieved by using the ratiometric approach so that complex circuits or high accuracy voltage references are not necessary. To prove the proposed architecture of R-T converter, a prototype was implemented in a 0.18

μ

m CMOS process with a single supply voltage of 1.8 V and without any stable reference voltage. Experimental results show a maximum ±1.5% output signal variation for ±10% supply voltage variation and in a 3–95

^{°}

C temperature range. Full article

(This article belongs to the Special Issue Electronic Interfaces for Sensors)

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