In this article, we propose a novel microfluidic microstrip electromagnetic band gap (EBG) sensor realized using cost-effective 3D printing technology. Microstrip sensor allows monitoring of the ...fluid properties flowing in the microchannel embedded between the microstrip line and ground plane. The sensor's operating principle is based on the phase-shift method, which allows the characterization at a single operating frequency of 6 GHz. The defected electromagnetic band gap (EBG) structure is realized as a pattern in the microstrip ground plane to improve sensor sensitivity. The designed microfluidic channel is fabricated using a fused deposition modelling (FDM) 3D printing process without additional supporting layers, while the conductive layers are realized using sticky aluminium tape. The measurement results show that the change of permittivity of the fluid in the microfluidic channel from 1 to 80 results in the phase-shift difference of almost 90°. The potential application is demonstrated through the implementation of a proposed sensor for the detection of toluene concentration in toluene-methanol mixture where various concentrations of toluene were analysed.
This paper presents an autonomous robotic system, an unmanned ground vehicle (UGV), for in-field soil sampling and analysis of nitrates. Compared to standard methods of soil analysis it has several ...advantages: each sample is individually analyzed compared to average sample analysis in standard methods; each sample is georeferenced, providing a map for precision base fertilizing; the process is fully autonomous; samples are analyzed in real-time, approximately 30 min per sample; and lightweight for less soil compaction. The robotic system has several modules: commercial robotic platform, anchoring module, sampling module, sample preparation module, sample analysis module, and communication module. The system is augmented with an in-house developed cloud-based platform. This platform uses satellite images, and an artificial intelligence (AI) proprietary algorithm to divide the target field into representative zones for sampling, thus, reducing and optimizing the number and locations of the samples. Based on this, a task is created for the robot to automatically sample at those locations. The user is provided with an in-house developed smartphone app enabling overview and monitoring of the task, changing the positions, removing and adding of the sampling points. The results of the measurements are uploaded to the cloud for further analysis and the creation of prescription maps for variable rate base fertilization.
This paper presents a very accurate sensor for the measurement of the moisture of undisturbed soil samples. The sensor relies on accurate estimation of the permittivity which is performed ...independently of the soil type, and a subsequent calibration. The sensor is designed as an upgrade of the conventional soil sampling equipment used in agriculture--the Kopecky cylinder. The detailed description of the device is given, and the method for determining soil moisture is explained in detail. Soil moisture of unknown test samples was measured with an absolute error below 0.0057 g/g, which is only 2.24% of the full scale output, illustrating the high accuracy of the sensor.
•Plant-O-Meter is suitable for low-cost, easy-to-perform, plant status measurements.•The device is supported by android app for generation of real-time maps of vegetation indices.•NDVI measured by ...the device was strongly correlated to the NDVI obtained by hyperspectral camera.•The performance of the device is not affected by the different illumination conditions.
Plant stress monitoring is of crucial importance to understand the plant response to environmental conditions, and has been widely applied in various fields including biology, agronomy, botany, and horticulture. A number of methods and instruments for plant stress monitoring have been proposed, most of which show significant disadvantages such as high cost, poor accuracy or complex operation that limit the use of such devices. In this paper, we propose a low cost, portable active multispectral optical device for precise plant stress detection and field mapping named Plant-O-Meter. The device has an integrated multispectral source that comprises light sources of the four most indicative wavelengths (850, 630, 535 and 465 nm), and enables simultaneous illumination of the whole plant. Sequential illumination and detection provide rapid reflectance measurements, which are wirelessly transmitted to android operated devices for processing and data storing. The device was tested in laboratory conditions comparing the Plant-O-Meter measurements with the image results from a SPECIM hyperspectral camera and a GreenSeeker handheld device and under field conditions with the GreenSeeker. The comparison revealed comparable performance, showing strong correlation with both the hyperspectral (R2 = 0.997) and the GreenSeeker handheld (R2 = 0.954 from the laboratory measurements and R2 = 0.886 from the field experiments), indicating that the device exhibits strong potential for accurate plant stress measurements. Moreover, owing to the very simple operating principle, the device represents a compact, cost-effective, and easy-to-operate solution.
Due to the global water crisis, there is a strong need for real-time water quality monitoring with high temporal and spatial resolutions. This article presents an economical multiparameter water ...quality monitoring system for continuous monitoring of fresh waters. It is based on a sensor node that integrates turbidity, temperature, and conductivity sensors, a miniature 18-channel spectrophotometer, and a sensor for the detection of thermotolerant coliforms, which is a major novelty of the system. Due to the influence of water impurities on the measurement of thermotolerant coliforms, a heuristic method has been developed to mitigate this effect. Moreover, the sensor is low power, and with an integrated long-range wide-area network module, it comprises a system that is wireless sensor network ready and can send data to a dedicated server. In addition, the system is submersible, capable of long-term field operation, and significantly cheaper in comparison to existing solutions. The purpose of the system is to give early warning of incidental pollution situations, thus enabling authorities to take action regarding further prevention of such occasions.
In this paper, we present two novel dual-band bandpass filters based on surface plasmon polariton-like (SPP-like) propagation induced by structural dispersion of substrate integrated waveguide (SIW). ...Both filters are realized as a three-layer SIW where each layer represents a sub-SIW structure with intrinsic effective permittivity that depends on its width and filling dielectric material. The layers are designed to have effective permittivities of opposite signs in certain frequency ranges, which enables SPP-like propagation to occur at their interfaces. Since three layers can provide two distinct SPP-like propagations, the filters exhibit dual-band behaviour. A detailed theoretical and numerical analysis and numerical optimization have been used to design the filters, which were afterwards fabricated using standard printed circuit board technology. The independent choice of geometrical parameters of sub-SIWs and/or the corresponding dielectric materials provide a great freedom to arbitrarily position the passbands in the spectrum, which is a significant advantage of the proposed filters. At the same time, they meet the requirements for low-cost low-profile configuration since they are realized as SIW structures, as well as for excellent in-band characteristics and selectivity which is confirmed by the measurement results.
In this paper, we propose a novel metamaterial-based microfluidic sensor that permits the monitoring of properties of the fluid flowing in the microfluidic reservoir embedded between the composite ...left–right handed (CLRH) microstrip line and the ground plane. The sensor’s working principle is based on the phase shift measurement of the two signals, the referent one that is guided through conventional microstrip line and measurement signal guided through the CLRH line. At the operating frequency of 1.275 GHz, the CLRH line supports electromagnetic waves with group and phase velocities that are antiparallel, and therefore the phase “advance” occurs in the case of CLRH line, while phase delay arises in the right-handed (RH) frequency band. The change of the fluid’s properties that flow in the microfluidic reservoir causes the change of effective permittivity of the microstrip substrate, and subsequently the phase velocity changes, as well as the phase shift. This effect was used in the design of the microfluidic sensor for the measurement of characteristics of the fluid that flows in the microfluidic reservoir placed under the CLRH line. The complete measurement system was developed including the Wilkinson power divider that splits the signal between conventional RH and CLRH section, transmission lines with the microfluidic reservoirs, and a detection circuit for phase shift measurement. Measurement results for different fluids confirm that the proposed sensor is characterized by relatively high sensitivity and good linearity (R2 = 0.94). In this study, the practical application of the proposed sensor is demonstrated for the biomass estimation inside the microfluidic bioreactors, which are used for the cultivation of MRC-5 fibroblasts.
► Characterization of NTC powders in a wide frequency and temperature range is made. ► Relative permittivity of NTC materials in the form of as-prepared powder determined. ► Measurement device for ...characterization of materials in powder form is proposed.
This paper presents a study of electrical properties of nickel manganite powder (NiMn2O4, NTC thermistor material) in a wide frequency range up to 1GHz, which is much needed for the development of NTC thermistors for mobile phones and other RF and microwave devices. The permittivity of nickel manganite has been analyzed as a function of frequency (100MHz–1GHz) and temperature (30–100°C), as well as for mechanically activated powders (milled for 5, 30 and 45min). To accurately measure the permittivity we have developed a robust, fast and low-cost device that enables repeated measurements at various temperatures. The detailed description of the device is given, and the method to determine permittivity of the sample is explained. We have found that the permittivity of nickel manganite powder decreases with the frequency for over 15%. In the same time, permittivity increases for almost 40% with the milling time and around 5% with the temperature.
Senzori vlažnosti zemljišta su od ključnog značaja za sisteme za navodnjavanje kojima je moguće uvećati prinose u proseku za 79%. U okviru ove disertacije razvijena su dva senzorska rešenja za ...merenje vlažnosti zemljišta. Prvi senzor je namenjen određivanju vlažnosti uzoraka zemljišta u neporemećenom stanju. Rešenje je nastalo nadogradnjom standardne opreme za uzorkovanje zemljišta. Za pomenuti senzor konstruisana je kalibraciona kriva kojom je moguće odrediti vlažnost zemljišta sa relativnom greškom ne većom od 2.5%. Drugo senzorsko rešenje je fabrikovano u LTCC tehnologiji, malih je dimenzija i namenjeno je primeni na terenu. Glavna prednost ovog senzora je da na njega ne utiče provodnost zemljišta koja je usko povezana sa tipom zemljišta. Predloženi senzor je testiran na dva uzorka zemljišta različitog hemijskog sastava. Rezultati merenja su pokazali da tip zemljišta nema uticaj na odziv senzora. Ostvarena relativna greška u odnosu na pun merni opseg iznosi 5.36%.
Soil moisture sensors are of great importance for the irrigation systems that
are able to increase the yiel on avarage of 79%. Within this thesis two sensor
solutions have been developed. The first sensor, which is intended for
laboratory use, has been designed by upgrading existing sampling
equipment. The constructed calibration curve for this type of sensor that can
be used for soil mositure determination with relative error not larger than
2.5% with respect to full scale output. The second sensor solution is
designed to be used in the field. It is fabricated in LTCC technology and it is
charaterized by small overall dimensions. The main advantage of this sensor
is that it is immune to the soil electrical conductivity which is closely related to
the soil type. Proposed sensor is tested on two soil sample of different
chemical composition and the results have shown that the type of soil does
not influence the sensor response. The relative error with the respect of full
scale output was only 5.36 %.
Senzori vlažnosti zemljišta su od ključnog značaja za sisteme za navodnjavanje kojima je moguće uvećati prinose u proseku za 79%. U okviru ove disertacije razvijena su dva senzorska rešenja za ...merenje vlažnosti zemljišta. Prvi senzor je namenjen određivanju vlažnosti uzoraka zemljišta u neporemećenom stanju. Rešenje je nastalo nadogradnjom standardne opreme za uzorkovanje zemljišta. Za pomenuti senzor konstruisana je kalibraciona kriva kojom je moguće odrediti vlažnost zemljišta sa relativnom greškom ne većom od 2.5%. Drugo senzorsko rešenje je fabrikovano u LTCC tehnologiji, malih je dimenzija i namenjeno je primeni na terenu. Glavna prednost ovog senzora je da na njega ne utiče provodnost zemljišta koja je usko povezana sa tipom zemljišta. Predloženi senzor je testiran na dva uzorka zemljišta različitog hemijskog sastava. Rezultati merenja su pokazali da tip zemljišta nema uticaj na odziv senzora. Ostvarena relativna greška u odnosu na pun merni opseg iznosi 5.36%.
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