Bojan M. Dakic

The possibility of using a plastic optical fibre as a sensing element in civil structural health monitoring

In this paper we propose a low-cost fibre-optic sensor, primarily intended for application in civil structural health monitoring. The sensor is based on a plastic optical fibre as a sensing element. The sensing optical fibre is optimized for measuring small curvature displacements. The behaviour of the sensor is first measured on flexible structures to achieve the characteristic of the sensor. In this paper, we perform the curvature gauge characterization and discuss the results. The characterized sensor is then mounted on a fragile material construction to investigate its potential for crack detection.

Design and simulation of 13.56 MHz RFID tag in ink-jet printing technology

This paper presents design, modeling and simulation cost-effective RFID (Radio Frequency Identification) tag using ink-jet printing technology. Passive 13.56 MHz RFID tag is based on an inductive-capacitive resonant circuit. Designed RFID tag is part of the ID (Identification) card, which has standard ISO ID1 size (85.60 mm × 53.98 mm). It consists of rectangular spiral planar inductor (antenna) and interdigital capacitor. The modeling and optimization of RFID tag are discussed. At the first step, inductor and capacitor were designed using in-house developed simulation tools AntInd and INDICON, respectively, in order to provide proper electrical characteristics of tag. After that, the designed geometrical structures are modeled and simulated using CST Microwave Studio software. A radiation pattern at operational frequency of 13.56 MHz simulated in CST of the RFID tag insulated in free spaces is presented.

Design of RFID antenna in ink-jet printing technology

In this paper design of 125 kHz RFID antenna is presented. The optimization and improvement of electrical characteristics, including inductance and Q-factor, is also discussed. Designed RFID antenna is part of the ID card, which has standard ISO ID1. It consists of two spiral coils in two layers. Comparison of antenna in flexible and PCB technology is presented. The aim of this work is to introduce novel cost-effective antenna in flexible technology instead of conventional RFID antenna in PCB technology.

An intensiometric contactless vibration sensor with bundle optical fiber for real time vibration monitoring

In this paper a low-cost fiber-optic intensity based vibration sensor is presented. As sensing element a bundle optical fiber was used. The sensor is based on changes of the reflected light intensity in bundle fiber which is placed near the vibrating element. As the vibrating element loudspeaker cone was used. The sensor was tested in the range of frequencies from 10 Hz to 1 kHz. The minimum detectable amplitude of vibration achieved is 1 μm. An application for real time vibration monitoring in LabVIEW software package was developed. The advantages of the proposed sensor are its simplicity, low-cost, immunity to electromagnetic interference, and the possibility of distributed and long term vibration monitoring over a single optical fiber link.

Analysis of Quantized Electrical Characteristics of Microscale TiO 2 Ink-Jet Printed Memristor

We demonstrate the ink-jet printed fabrication technique for TiO2-based memristor, followed by detailed analysis of electrical characteristics and development of a new model that considers observed phenomena of quantized conductance steps. The existence of pinched hysteretic current-voltage characteristics is evidence of memristive behavior, provided by the reversible atomic rearrangement taking place in the functional layer. For the first time, performed electrical measurement on the micrometer thickness devices based on TiO2 active layer has captured the plateaux steps of the conductance at integer multiples of elementary quantum conductance. This behavior is consistent with the assumption that transport from electrode to electrode emerges through confined paths of conductive filaments with radius in the nanometer size range. Moreover, we introduce a novel model, based on the diffusion equation for ballistic transport in memristive devices, which considers the conductance plateaux steps.

A Novel Fiber-Optic Mass Flow Sensor

In this paper a novel fiber-optic mass flow sensor based on coriolis force is presented. As sensing elements two fiber-optic curvature sensors mounted on elastic rubber tube are used. Rubber tube with sensing elements is excited by stepper motor. Produced system has the option of varying angle and speed of excitation. The bending of the fibers at the sensitive zone on curvature sensor changes the intensity of light traveling through the optical fiber. Curvature sensors are attached to the rubber tube so that they can measure phase difference produced by coriolis force. Mass flow rate is obtained by digital signal processing technique for phase difference detection.

Remote monitoring of water salinity by using side-polished fiber-optic U-shaped sensor

In this paper, a remote water salinity measurement system based on a simple and low-cost intensity based side-polished fiber-optic U-shaped sensor is presented. The sensor system utilizes a side-polished U-shaped configuration in order to maximize the sensitivity and expand the measurement range. The implemented salinity sensor is made of a multimode plastic optical fiber, and sensor determines the salinity by measuring the refractive index. Measurement resolution and uncertainty of proposed salinity sensor are 0.001 and 0.002, respectively. Wireless electronics based on ZigBee protocol is also implemented. Therefore, the sensor has the possibility of wireless measurements. The main advantages of this sensor are simplicity, lightness and flexibility. This sensor is also electrically safe and immune to electromagnetic interferences. In LabVIEW software package client and server applications are implemented, which gives a possibility of remote monitoring of water salinity over the internet.

Implementation and characterization of a fibre-optic colour sensor

In this paper the implementation of a fibre-optic sensor for colour detection based on reflective colour sensing is proposed. The sensor consists of three plastic optical fibres emitting red, green and blue components and one optical fibre collecting light reflected from the object. Red, green and blue LEDs are excited at different frequencies. In this way detection of the reflected signal is achieved with only one photodetector and three bandpass filters. Bandpass filters are implemented as digital IIR (infinite impulse response) filters on the microcontroller. Results obtained from the proposed sensor are compared with commercial available colour sensors and the results are satisfactory. Analyses of the sensor performance both in RGB and HSV colour space are done. The proposed solution shows that in specific applications by using the HSV model the sensor can be used both as a colour and distance sensor.

An End-Type Fiber-Optic UV Sensor Covered with Mixture of Two UV Sensitive Materials

An end-type fiber-optic UV sensor based on the principle of fluorescence is proposed and demonstrated. The sensor is made of large-core plastic optical fiber with one end covered with mixture of hot melt adhesive and small amount of chlorophyll. As sources of ultraviolet radiation solar simulator and UV lamp are used. Spectra on the sensor output are measured with spectrometer and compared for different UV light sources. Both hot melt adhesive and chlorophyll reacted to UV radiation. The peaks of fluorescent emission are obtained in visible spectrum in range of blue wavelengths (for hot melt adhesive) and in range of red wavelengths (for chlorophyll), which makes this sensor configuration a good solution for signal multiplexing.