A VHDL Model of a IEEE1451.2 Smart Sensor: Characterization and Applications

New sensors are required to be small, cheap, and smart. This paper deals with intelligent sensors embedded in a single chip: a VHDL model of an IEEE1451.2 Smart Sensor is proposed to obtain a portable STIM block suitable for customizable compact solutions and allowing low-cost, large-scale production. In order to evaluate performances of the proposed model, working prototypes have been built and some tests have been carried out in a real case (chemical detection sensors). The proposed VHDL model has been compared with traditional, software-based, microcontroller solutions showing that a timing performance improvement greater than 50% can be obtained. Finally, to exemplify effectiveness of a portable VHDL model, a single-chip sensor with USB interface and integrated IEEE1451 structures has been realized and experimentally characterized     

A New Instrument for Real-Time Ethernet Performance Measurement

Ethernet is now becoming a popular physical layer for industrial communications due to its reliability, performance, and widespread use. Its actual cutting edge is a minimum cycle time on the order of 100 mus and a jitter of 1 mus. Usually, high-cost laboratory devices are used to log network traffic, but they are still not suitable for an industrial environment. In this paper, a field-programmable-gate-array-based instrument is proposed to log 100-Mb/s Ethernet frames, assigning them a high-resolution time stamp. Full-duplex full-rate network traffic is duplicated and sent through two auxiliary Ethernet ports to a personal-computer-based monitor station for frame analysis. A prototype has been realized to verify feasibility and performance. Results show that the proposed instrument introduces a maximum delay of about 500 ns. The measurement capabilities are comparable with commercial instruments: The time-stamp assignment has a jitter of 150 ns measured on a test frame set.     

Application of an ANFIS Algorithm to Sensor Data Processing

Some sensors require frequent recalibrations; therefore, calibration cost must be limited. In this paper, a new calibration technique is presented. It is a two-phase method which is based on adaptive neuro-fuzzy networks, and it shows superior performances with respect to traditional algorithms, requiring fewer calibration points and less computational power in the recalibration phase. Feasibility has been demonstrated with a pyroelectric biaxial positioning system, reaching performance to the limit of the adopted test bench, on the order of 20 mum with respect to a whole sensible area of 7 mm times 7 mm     

A CMOS Integrable Oscillator-Based Front End for High-Dynamic-Range Resistive Sensors

A new oscillating circuit is proposed to estimate the resistance and parallel parasitic capacitance of resistive chemical sensors. The circuit is able to reveal the resistance in a wide range (from tens of kiloohms to more than 100 $hbox{G}Omega$) due to the adopted resistance-to-time technique. In addition, the parallel capacitance (up to 50 pF) can be estimated. The circuit, which does not need any initial calibration, is very simple and compact and is suitable to be integrated with a standard CMOS technology to obtain a low-cost and low-power device for a sensor array interface. Different kinds of postlayout simulations concerning the CMOS integrated implementation have been conducted. Experimental results obtained using a discrete prototype board, both on passive components and on real sensors (metal–oxide sensors), have shown good linearity and reduced percentage error with respect to the theoretical expectations.      

Digital signal processing for biaxial position measurement with a pyroelectric sensor array

This paper proposes a new full digital approach to estimate biaxial position with a pyroelectric sensor array. The previously developed analog interface shows its limits in the calibration procedure, requiring several trimming adjustments. A DSP-based hardware has been developed to experimentally evaluate three digital methods: radial basis function (RBF) neural network, best fitted plane (BFP), and look-up table (LUT) in the least mean square (LMS) error sense. Experimental results show that no dramatic improvements are obtained by the RBF, despite the long training required and the external PC support for weight calculation. The BFP reaches performances comparable to the analog processing system using only nine calibration points, but the best tradeoff has been found with the LUT technique. Actually, with a 64-point calibration set, LUT gives a root mean square error (RMSE) of 0.5% with respect to full scale (FS), offering a valid in-circuit compensation of array structural defects.     

A new 0.35 μm CMOS electronic interface for wide range floating capacitive and grounded/floating resistive sensor applications

In this paper we propose a novel interface circuit suitable for the read-out of both wide range floating capacitive and grounded/floating resistive sensors. This solution, employing only two Operational Amplifiers (OAs) as active blocks and some passive components, is based on a square-wave oscillating circuit topology which, instead of a voltage integration typically performed by other solutions in the literature, operates a voltage differentiation. Therefore, the proposed circuit, performing an impedance-to-period (Z–T) conversion, results to be suitable as first analog front-end for both wide variation capacitive (e.g., relative humidity) and resistive (e.g., gas) sensors. Its sensitivity and dynamic range can be easily set through external passive components. Preliminary experimental measurements, which have characterized and validated this solution, have been conducted through a suitable prototype PCB fabricated with discrete commercial components. Then, the proposed interface has been also designed at transistor level, in a standard CMOS technology (AMS 0.35 um), developing a single-chip integrated circuit with low-voltage (1.8 V, single supply) low-power (about 350 μW) characteristics in a very small silicon area (lower than 0.6 mm²) which results to be suitable for sensor array configurations and portable applications. Further experimental results, achieved utilizing commercial sample resistors and capacitors to emulate sensor behavior, have shown a linear trend and a satisfactory accuracy in the evaluation of floating capacitive (in the range 10 pF–1 μF), grounded resistive (in the range 150 kΩ–1.5 MΩ) and floating resistive (in the range 10 MΩ–1 GΩ) variations, also when compared to other solutions presented in the literature. The satisfactory interface behavior has been also confirmed by the measurement of both relative humidity through the commercial sensor Honeywell HCH-1000 (capacitive) and carbon monoxide CO through the commercial air quality sensor FIGARO TGS-2600 (resistive).     

Model and Experimental Characterization of the Dynamic Behavior of Low-Power Carbon Monoxide MOX Sensors Operated With Pulsed Temperature Profiles

Wireless sensor networks for home automation or environment monitoring require low-cost low-power sensors. Carbon monoxide (CO) metal-oxide (MOX) sensors could be suitable in terms of device cost, but they show some severe limits, such as the need to be heated, which means large power consumption and the need for complex and frequent calibration procedures, which increases the overall cost. This paper investigates the possibility to partially overcome these limits by a low-cost detection system based on a suitable commercial sensor (TGS 2442, Figaro, Inc.) and an ad hoc measurement technique exploiting specifically tailored temperature profiles. To this aim, the authors study the dynamic behavior of low-power CO MOX sensors operated with pulsed temperature profiles by means of two approaches: 1) sensor modeling and 2) experimental evaluation. To analyze how the sensor dynamic response changes as a function of the CO concentration, the authors individuate a temperature profile, which ensures satisfactory sensitivity to the target gas and very low power consumption. Moreover, some parameters describing the sensor response shape are selected, which prove to be significant in terms of both robustness to environmental conditions and calibration simplicity.     

Programmable logic device-based interface for resonant sensor arrays

A simple and successful approach for signal frequency estimation is presented. If applied to multichannel measurements (i.e. resonant sensors arrays) this method allows smaller implementation compared to classical techniques (e.g. CET). A prototype has been developed to evaluate the algorithm and the measured data agree with predicted results.     

USB Sensor Network for Industrial Applications

This paper proposes a universal serial bus (USB) solution for sensor networking. First, network architecture has been presented to have, as its primary objective, its integration with existing infrastructure. For this reason, a USB-to-Ethernet gateway has been introduced. Then, many aspects of industrial applications have been considered to realize a suitable solution. Insulation problems and low-cost implementation have been tackled. Working prototypes of each network component have been defined and realized: USB host gateway, USB insulator, and USB hub. Several commercial USB devices can be used as sensors. Finally, some experiments have been carried out: Timing performances, network activities, and power consumption have been tested.     

A New Low-Cost Electronic System to Manage Resistive Sensors for Gas Detection

In this paper, a new electronic system for gas detection is presented. Particular attention is focused on electronic noses that employ several resistive sensors. New resistive sensors may have high value due to new substances (TiO₂) or to low-cost fabrication process and, supposing to use these sensors together with traditional ones (SnO₂), a novel instrument to manage high-value resistive sensors varying over a wide range, from kilohms to gigohms is required. The proposed hardware approach is a modular architecture which takes advantage from an improved resistance-to-period converter, where sensors are DC powered. Experimental results show a relative standard deviation below 0.01% and a relative displacement to the reference line less than 1% over six decades if commercial resistors are considered. A prototype has been realized to manage up to eight sensors, detect and estimate substance concentrations, and communicate results to the Internet.