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The continuous monitoring of soil water content is commonly carried out using low-frequency capacitance sensors that require a site-specific calibration to relate sensor readings to apparent dielectric bulk permittivity (Kb) and soil water content (θ). In fine-textured soils, the conversion of Kb to θ is still challenging due to temperature effects on the bound water fraction associated with clay mineral surfaces, which is disregarded in factory calibrations. Here, a multi-point calibration approach accounts for temperature effects on two soils with medium to high clay content. A calibration strategy was developed using repacked soil samples in which the Kb-θ relationship was determined for temperature (T) steps from 10 to 40 °C. This approach was tested using the GS3 and TEROS-12 sensors (METER Group, Inc. Pullman, WA, USA; formerly Decagon Devices). Kb is influenced by T in both soils with contrasting T-Kb relationships. The measured data were fitted using a linear function θ = a K b + b with temperature-dependent coefficients a and b. The slope, a(T), and intercept, b(T), of the loam soil were different from the ones of the clay soil. The consideration of a temperature correction resulted in low RMSE values, ranging from 0.007 to 0.033 cm3 cm−3, which were lower than the RMSE values obtained from factory calibration (0.046 to 0.11 cm3 cm−3). However, each experiment was replicated only twice using two different sensors. Sensor-to-sensor variability effects were thus ignored in this study and will be systematically investigated in a future study. Finally, the applicability of the proposed calibration method was tested at two experimental sites. The spatial-average θ from a network of GS3 sensors based on the new calibration fairly agreed with the independent area-wide θ from the Cosmic Ray Neutron Sensor (CRNS). This study provided a temperature-corrected calibration to increase the accuracy of commercial sensors, especially under dry conditions, at two experimental sites. [ABSTRACT FROM AUTHOR]

Propellant mass gauging under micro-gravity conditions is a challenging task due to the unpredictable position and shape of the fuel body inside the tank. Micro-gravity conditions are common for orbiting satellites and rockets that operate on limited fuel supplies. Capacitance sensors have been investigated for this task in recent years; however, the effect of various positions and shapes of the fuel body is not analyzed in detail. In this paper, we investigate this with various fill types, such as annular, core-annular, and stratified fills at different positions. We compare the performance among several curve-fitting-based approaches and a machine-learning-based approach, the latter of which offers superior performance in estimating the fuel content. [ABSTRACT FROM AUTHOR]

In recent years, laser engraving has received widespread attention as a convenient, efficient, and programmable method which has enabled high-quality porous graphene to be obtained from various precursors. Laser engraving is often used to fabricate the dielectric layer with a microstructure for capacitive pressure sensors; however, the usual choice of electrodes remains poorly flexible metal electrodes, which greatly limit the overall flexibility of the sensors. In this work, we propose a flexible capacitive pressure sensor made entirely of thermoplastic polyurethane (TPU) and laser-induced graphene (LIG) derived from wood. The capacitive pressure sensor consisted of a flexible LIG/TPU electrode (LTE), an LIG/TPU electrode with a microhole array, and a dielectric layer of TPU with microcone array molded from a laser-engraved hole array on wood, which provided high sensitivity (0.11 kPa−1), an ultrawide pressure detection range (20 Pa to 1.4 MPa), a fast response (~300 ms), and good stability (>4000 cycles, at 0–35 kPa). We believe that our research makes a significant contribution to the literature, because the easy availability of the materials derived from wood and the overall consistent flexibility meet the requirements of flexible electronic devices. [ABSTRACT FROM AUTHOR]

The continuous monitoring of soil water content is commonly carried out using low-frequency capacitance sensors that require a site-specific calibration to relate sensor readings to apparent dielectric bulk permittivity (Kb) and soil water content (θ). In fine-textured soils, the conversion of Kb to θ is still challenging due to temperature effects on the bound water fraction associated with clay mineral surfaces, which is disregarded in factory calibrations. Here, a multi-point calibration approach accounts for temperature effects on two soils with medium to high clay content. A calibration strategy was developed using repacked soil samples in which the Kb-θ relationship was determined for temperature (T) steps from 10 to 40 °C. This approach was tested using the GS3 and TEROS-12 sensors (METER Group, Inc. Pullman, WA, USA; formerly Decagon Devices). Kb is influenced by T in both soils with contrasting T-Kb relationships. The measured data were fitted using a linear function θ = aKb + b with temperature-dependent coefficients a and b. The slope, a(T), and intercept, b(T), of the loam soil were different from the ones of the clay soil. The consideration of a temperature correction resulted in low RMSE values, ranging from 0.007 to 0.033 cm3 cm−3, which were lower than the RMSE values obtained from factory calibration (0.046 to 0.11 cm3 cm−3). However, each experiment was replicated only twice using two different sensors. Sensor-to-sensor variability effects were thus ignored in this study and will be systematically investigated in a future study. Finally, the applicability of the proposed calibration method was tested at two experimental sites. The spatial-average θ from a network of GS3 sensors based on the new calibration fairly agreed with the independent area-wide θ from the Cosmic Ray Neutron Sensor (CRNS). This study provided a temperature-corrected calibration to increase the accuracy of commercial sensors, especially under dry conditions, at two experimental sites.

From the actual development and testing requirements of horizontal wells in domestic oilfields, according to the problems that the common sensors have relatively low resolution during the water cut measurement for the oil–water flow in the horizontal wells with medium and low production, a trielectrode capacitance sensor (TECS) is designed and a water cut measurement system based on TECS is developed for different conditions of horizontal oil–water flow. Specifically, the electrostatic field distribution of the annular measurement region is investigated under different conditions of horizontal stratified flow. Then, its equivalent capacitance on the electrodes is analyzed. Based on the simulated results, the effects of structural parameters on sensitivity distribution are analyzed, including the electrode length, the radius of the flow channel, and the thickness of the insulation, determining its optimal structure. Moreover, the static and dynamic experiments, as well as the field testing, validate the designed TECS, indicating that the TECS enables measuring the water cut of horizontal oil–water flow, especially under low flow rate and oil–water stratified conditions. The developed TECS could realize the water cut measurement with a wide flow rate range (3–60 m $^3$ /d) and the full water cut range (0%–100%) for the horizontal oil–water flow. [ABSTRACT FROM AUTHOR]

Propellant mass gauging under micro-gravity conditions is a challenging task due to the unpredictable position and shape of the fuel body inside the tank. Micro-gravity conditions are common for orbiting satellites and rockets that operate on limited fuel supplies. Capacitance sensors have been investigated for this task in recent years; however, the effect of various positions and shapes of the fuel body is not analyzed in detail. In this paper, we investigate this with various fill types, such as annular, core-annular, and stratified fills at different positions. We compare the performance among several curve-fitting-based approaches and a machine-learning-based approach, the latter of which offers superior performance in estimating the fuel content.

In recent years, laser engraving has received widespread attention as a convenient, efficient, and programmable method which has enabled high-quality porous graphene to be obtained from various precursors. Laser engraving is often used to fabricate the dielectric layer with a microstructure for capacitive pressure sensors; however, the usual choice of electrodes remains poorly flexible metal electrodes, which greatly limit the overall flexibility of the sensors. In this work, we propose a flexible capacitive pressure sensor made entirely of thermoplastic polyurethane (TPU) and laser-induced graphene (LIG) derived from wood. The capacitive pressure sensor consisted of a flexible LIG/TPU electrode (LTE), an LIG/TPU electrode with a microhole array, and a dielectric layer of TPU with microcone array molded from a laser-engraved hole array on wood, which provided high sensitivity (0.11 kPa−1), an ultrawide pressure detection range (20 Pa to 1.4 MPa), a fast response (~300 ms), and good stability (>4000 cycles, at 0–35 kPa). We believe that our research makes a significant contribution to the literature, because the easy availability of the materials derived from wood and the overall consistent flexibility meet the requirements of flexible electronic devices.

Soft and flexible strain sensors are becoming popular for many robotic applications. This article presents a stretchable capacitive sensor by combining a conductive filler of carbon black with elastomers and implementing shielding to reduce parasitic interference, applied to an underactuated robotic hand. Sensors with different configurations were explored. The results show that a shield introduced to the sensor does have some mitigation effect on external interference. Two sensor configurations were explored: longitudinal interdigitated capacitive (LIDC) sensor, where the interdigitated fingers lie along the same axis as the strain, and transverse interdigitated capacitive (TIDC) sensor, where the interdigitated fingers are orthogonal to the strain direction. The LIDC configuration had better performance than TIDC. The fabricated two-layered LIDC sensor had a gage factor of 0.15 pF/mm and the rates of capacitive creep of 0.000667 pF/s and 0.001 pF/s at loads of 120 g and 180 g, respectively. The LIDC sensors attached to an underactuated robotic hand demonstrate the sensors' ability to determine the bending angles of the proximal interphalangeal (PIP) and metacarpophalangeal (MCP) joints. [ABSTRACT FROM AUTHOR]

Soft and flexible strain sensors are becoming popular for many robotic applications. This article presents a stretchable capacitive sensor by combining a conductive filler of carbon black with elastomers and implementing shielding to reduce parasitic interference, applied to an underactuated robotic hand. Sensors with different configurations were explored. The results show that a shield introduced to the sensor does have some mitigation effect on external interference. Two sensor configurations were explored: longitudinal interdigitated capacitive (LIDC) sensor, where the interdigitated fingers lie along the same axis as the strain, and transverse interdigitated capacitive (TIDC) sensor, where the interdigitated fingers are orthogonal to the strain direction. The LIDC configuration had better performance than TIDC. The fabricated two-layered LIDC sensor had a gage factor of 0.15 pF/mm and the rates of capacitive creep of 0.000667 pF/s and 0.001 pF/s at loads of 120 g and 180 g, respectively. The LIDC sensors attached to an underactuated robotic hand demonstrate the sensors’ ability to determine the bending angles of the proximal interphalangeal (PIP) and metacarpophalangeal (MCP) joints.

Water scarcity in semi-arid regions is expected to increase under climate change, which will significantly affect forest ecosystems by increasing fire risk, diminishing productivity and water provisioning. Eco-hydrological forest management is conceived here as an adequate strategy to buffer climate change effects and increase forest resilience. Under this context, soil moisture is a key variable to quantify the impacts of eco-hydrological forest management on forest-water relations. Cosmic-ray neutron and capacitance probes are two different techniques for measuring soil moisture, which differ greatly in the spatial scale of the measurement support (i.e., few centimeters vs. several hectares). This study compares the capability of both methodologies in assessing soil water dynamics as a key variable that reflects the effects of forest management in a semi-arid environment. To this end, two experimental plots were established in Sierra Calderona in the province of Valencia in Spain in a post-fire regeneration Aleppo pine forest with high tree density. One plot was thinned (T) and the other remained as control (C). Nine capacitance probes and one Cosmic Ray Neutron Probe (CRNP) were installed in each plot. First, the CRNP was calibrated and validated, and subsequently, the performance of both techniques was analyzed by comparing soil moisture and its relationship with environmental variables and stand transpiration. The validation results confirmed the general reliability of CRNP to obtain soil moisture under semi-arid conditions, with a Kling-Gupta efficiency coefficient (KGE) between 0.75 and 0.84, although this performance decreased significantly when dealing with extreme soil moisture (KGE: −0.06–0.02). A significant effect of forest biomass and litter layer was also observed on CRNP-derived soil moisture, which produced an overestimation of soil moisture. The performance of both methodologies was analyzed by partial correlations between soil moisture and environmental variables and transpiration, as well as by applying Boosted Regression Trees to reproduce tree transpiration with each soil moisture measurement technique together with the environmental variables. Both methodologies were capable to reproduce tree transpiration affected by soil moisture, environmental variables and thinning, although CRNP always appeared as the most affected by atmospheric driving forces.

Copyright of Technisches Messen is the property of De Gruyter and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Knowledge on the water content of a certain soil profile and its temporal changes due to rainfall and plant water uptake is a key issue for irrigation management. In this regard, sensors can be utilized to monitor soil water content (SWC). Due to the characteristic spatial variability of SWC, a key question is whether the measurements are representative and reliable. This study focused on the assessment of SWC and its variability in a vineyard with subsurface drip irrigation. SWC was measured in profiles down to a 50 cm depth by means of multi-sensor capacitance probes. The probes were installed at six locations along vine rows. A temporal stability analysis was performed to evaluate the representativeness and reliability of each monitoring profile with regard to irrigation control. Mean SWC was within a plausible range compared to unsaturated hydraulic parameters determined in a laboratory. The measurements revealed a considerable variability, but standard deviations were comparable to values from literature. The main finding was that some monitoring profiles (probes) proved to be more suitable to monitor SWC with respect to irrigation control than the others. Considering temporal stability provided helpful insights into the spatio-temporal variability of SWC measurements. However, not all questions that are related to the concept of temporal stability could be answered based on the given dataset.

Copyright of Journal of Engineering (17264073) is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The need for two-phase flow measurement in the power generation industry has been significantly increased over the last few years. This is mainly because the reliable measurements of the two-phase flow parameters, such as void fraction, phase velocity, and flow pattern identification, are important for accurate modeling and/or in the operation of energy systems. Although many two-phase flow sensors were recently developed, challenges in measuring two-phase flow characteristics using a simple and inexpensive sensor remain unresolved. Therefore, extensive research efforts that were spent in designing accurate two-phase flow sensor that does not require complex software solving an inverse problem are currently under development worldwide. In this paper, a multichannel, high-resolution capacitance sensor system for two-phase flow void fraction measurements was developed for slightly conductive and non-conductive fluids. Inductance–capacitance ($LC$) metering circuit is designed to relate the change in the measured resonance frequency to the change in capacitance registered by the sensor. The narrow band filtering effect of the $LC$ circuit allows for the system to be more resistant to background noise. Three sensor electrode configurations were designed in order to provide more information on the flow behavior in the piping system, including the bubble velocity, flow distribution, and time signal of void fraction for different flow patterns. Both static and dynamic measurements were carried out, and the sensor operation was validated using a high-speed imaging system. [ABSTRACT FROM AUTHOR]

Chufa is a typical crop in Valencia, Spain, where it is cultivated in ridges with furrow irrigation. It uses large volumes of water, and thus, different studies have been undertaken to maximize irrigation water use efficiency to obtain important water savings. Particularly, different values for turning water on, considering the basis of volumetric soil water content were analysed in drip irrigation. It was reported that starting each irrigation event when the volumetric soil water content dropped to 90% of the field capacity resulted in the best yield, and the best irrigation water use efficiency was obtained when it dropped to 80% of the field capacity. However, these results may be improved by defining the optimum criteria for turning water off, which is the aim of the present research. This investigation, conducted in 2015, 2016 and 2017, analises the productive response of the drip irrigated chufa crop, determining the yield and the irrigation water use efficiency. The volumetric soil water content was monitored using multi-depth capacitance probes, with sensors at 0.10, 0.20 and 0.30 m below the top of the ridge. Each irrigation event started when the volumetric soil water content at 0.10 m dropped to 85% of field capacity. Three irrigation strategies were considered. T1: each event resulting in water being turned off when the sum of the volumetric soil water content values that were measured at 0.10, 0.20 and 0.30 m reached the corresponding field capacity value; T2: turning water off in each event when the volumetric soil water content values that were measured at 0.20 m reached the corresponding field capacity value; and T3: each irrigation event applying 8.5 mm in 2015 and 2016, as well as 9.8 mm in 2017. Overall, the T2 strategy resulted in the largest yield, and T3 resulted in the highest irrigation water use efficiency in 2015 and 2016. The average tuber weight and dry matter content did not differ between the irrigation strategies. [ABSTRACT FROM AUTHOR]

Void fraction plays a vital role in diverse industries like oil, petrochemical, etc., which involve a wide range of fluids, including two-phase and three-phase fluids. Various procedures are used for the measurement of the void fraction, with one of the most popular being capacitance-based sensors. The characteristics of the fluid inside the pipe affect the output of this type of sensor, and every property, such as temperature, pressure, and density, plays a role. This paper presents the use of an Artificial Neural Network (ANN) and a combined capacitance-based sensor to measure the void fraction of a two-phase air-water homogeneous fluid. The aim is to develop a system that can predict void fraction independent of temperature and pressure changes. To achieve this, the COMSOL Multiphysics software was used to design and simulate two widely used sensors, concave and ring, to create a combined capacitance sensor. Simulations were conducted for the implemented sensor in different temperature ranges (275–370 K) and pressure ranges (1–500 Bar). After a large number of simulations and producing 3780 data from the combined sensor, they were used as inputs to train the proposed MLP ANN network. The presented model provides a new metering system that can accurately estimate the amount of the void fraction of a two-phase air-water homogeneous fluid independent of temperature and pressure changes and had a low error which means the MAE is equal to 4.868. • A combined capacitive sensor and ANN were used to measure the void fraction. • This system can measure void fraction independent of temperature and pressure. • COMSOL was used to design and simulate the combined capacitive sensor. • After a large number of simulations, they were used as inputs of MLP network. • The MAE of presented system is equal to 4.868 which is a low error. [ABSTRACT FROM AUTHOR]

A capacitance measurement system is developed for the measurement of gas-liquid two-phase flow in glass micro-pipes with inner diameters of 3.96, 2.65 and 1.56 mm, respectively. As a typical flow regime in a micro-pipe two-phase flow system, slug flow is chosen for this investigation. A capacitance sensor is designed and a high-resolution and high-speed capacitance measurement circuit is used to measure the small capacitance signals based on the differential sampling method. The performance and feasibility of the capacitance method are investigated and discussed. The capacitance signal is analyzed, which can reflect the voidage variation of two-phase flow. The gas slug velocity is determined through a cross-correlation technique using two identical capacitance sensors. The simulation and experimental results show that the presented capacitance measurement system is successful. Research work also verifies that the capacitance sensor is an effective method for the measurement of gas liquid two-phase flow parameters in micro-pipes.

A design of a capacitance sensor, which remains highly sensitive while allowing the significant miniaturization of its sensitive element, the condenser, is proposed. For this purpose, supercondensers based on electroconducting and insulating nanotubes are used. The presented calculations show the possibility, in principle, to create pressure and displacement capacitance sensors on this basis with a sensitivity that is 5-6 orders of magnitude higher than the sensitivity of those based on classical carbon nanotubes. Such sensors can be used in medicine, robotics, and nanoelectronics. [ABSTRACT FROM AUTHOR]

Knowledge on the water content of a certain soil profile and its temporal changes due to rainfall and plant water uptake is a key issue for irrigation management. In this regard, sensors can be utilized to monitor soil water content (SWC). Due to the characteristic spatial variability of SWC, a key question is whether the measurements are representative and reliable. This study focused on the assessment of SWC and its variability in a vineyard with subsurface drip irrigation. SWC was measured in profiles down to a 50 cm depth by means of multi-sensor capacitance probes. The probes were installed at six locations along vine rows. A temporal stability analysis was performed to evaluate the representativeness and reliability of each monitoring profile with regard to irrigation control. Mean SWC was within a plausible range compared to unsaturated hydraulic parameters determined in a laboratory. The measurements revealed a considerable variability, but standard deviations were comparable to values from literature. The main finding was that some monitoring profiles (probes) proved to be more suitable to monitor SWC with respect to irrigation control than the others. Considering temporal stability provided helpful insights into the spatio-temporal variability of SWC measurements. However, not all questions that are related to the concept of temporal stability could be answered based on the given dataset. [ABSTRACT FROM AUTHOR]

An accurate and comprehensive assessment of platelet function is essential for managing patients who receive antiplatelet therapies or require platelet transfusion either for treating active bleeding or for prophylaxis. Platelets contribute to clotting by undergoing a series of highly regulated functional responses including adhesion, spreading, granular secretion, aggregation, and cytoskeletal contraction. However, current platelet function assays evaluate only partial aspects of this intricate process and often under non-physiological testing conditions. Herein, we describe the development of a new approach to measure multiple key platelet function-related parameters, in a more physiologically relevant ex vivo semi-rigid microenvironment using a membrane capacitance sensor (MCS). MCS response to clotting provided three sensing parameters with sensitivities towards platelet counts, stimulation strengths, and activation pathways. Live confocal fluorescent imaging of stimulated platelets on MCS suggests that the presented system can readily and accurately convert the dynamics of cytoskeletal reorganization into analyzable electrical signals. Together, this new completely electrical sensing platform can be a promising diagnostic venue to recognize the impairment of primary hemostatic functions, evaluate the efficacy of therapeutic interventions, and gain further insights into the mechanisms of platelets in hemostasis and thrombosis. [ABSTRACT FROM AUTHOR]

Chufa (Cyperus esculentus L. var. sativus Boeck.) is an important vegetable crop in Valencia (Spain), where its tubers are used to produce a refreshing drink called 'horchata'. Water is relatively inexpensive, there are no data regarding the volumes of water used to grow chufa, and the irrigation water use efficiency (IWUE) has neither been determined. The aim of this research was to compare the productive responses of the chufa crop to two irrigation strategies (IS). The volumetric soil water content (VSWC) was monitored with capacitance sensors. Trends in VSWC were used to determine the in situ field capacity (FC), beginning each irrigation event when the VSWC reached either approximately 45% (H1) or 60% (H2) of the FC at a soil depth of 0.10 m. The experiments were conducted over three consecutive seasons. An area velocity flow module measured the water flow. The yields, the water volumes used, and the IWUE were calculated. Plants were periodically sampled and the harvest index and relative growth rate were determined. The yield was affected by the year and by the IS. The greatest yields were obtained with the H2 strategy (on average 2.18 kg m-2 for H2 vs. 1.94 kg m-2 for H1; p≤0.01), and the average tuber weight (ATW) was affected (p≤0.01) by the year and IS interaction. IWUE was affected by the year, and none of the considered factors affected the harvest index (p≤0.05). It can be concluded that maintaining a higher VSWC would increase both yield and ATW without affecting IWUE.

An instrumentation technique is developed using embedded capacitive sensors to measure the thickness and evenness of coverage of a thin layer of dielectric thermal interface material (TIM) between two substrates. The technique requires an array of sensors embedded into one substrate, with an electrically conductive opposing substrate. Local capacitance measurements are sensitive to both local bond layer thickness and local voiding. We propose a means for using an array of capacitance measurements to interpret both bond layer thickness and local voiding at every sensor location. An algorithm is developed which reveals both characteristics from a single set of capacitance measurements. Experiments are conducted with thermal grease layers of different bond layer thicknesses and void distributions using a prototype system constructed on printed circuit boards. The thickness and void distribution are successfully mapped across the bond layer using the algorithm developed. The technique offers a sensing approach for in situ instrumentation of layers of thermal grease in a thermal test vehicle. [ABSTRACT FROM AUTHOR]

The paper reports a capacitive sensor for measuring liquid level which was fully fabricated with the inkjet printing technology. The liquid level measurement based on capacitive sensing is already well known technique. The novelty of presented capacitive sensor is used technology, obtained structure flexibility and its dimension. The sensor structure was printed on a thin Kapton substrate with dimensions of 210 mm x 12 mm, and the thickness approximately 27 μm. The sensor was tested on a vessel witch was filled and emptied with water. The tests shown sensor linearity in liquid level sensing and the lack of hysteresis. Obtained sensitivity of the prototype sensor was approximately 74·10 -3 pF/mm. The sensor structure can be applied to any shape of vessel. Furthermore, its construction is very simple and in mass production costs could be extremely low. This type of sensor was designed especially for autonomous cleaning and washing machines for large areas. [ABSTRACT FROM AUTHOR]

Reliable and affordable moisture sensors with a simplified calibration process for obtaining the water content information of soil/soilless substrates were limited. In this paper, an unilateral sensitive capacitive soil moisture sensor, based on the improved ECH2O sensor probe structure, was presented. Through simulating the relationship between the ratio of plate space and plate width ( $a/b$ ) and probe sensitivity, sensitive depth, respectively, the size of the sensor was determined with ANSYS first. Capacitance measurement circuit based on resonant principle was then designed. The relationship between the output of the sensor and the soil water content calibration model ( \beta $ parameter model), was investigated. As a result, we proposed a two-step calibration \beta $ method. Experimental results showed that \beta in the soil, peat, perlite, and vinegar residue. The measurement error of $\beta $ parameter model was <0.025 units except in perlite. The error caused by the change of bulk density was <0.025 units in peat and vinegar residue. Therefore, the two-step calibration $\beta $ method is suitable for calibrating the sensor. [ABSTRACT FROM PUBLISHER]

The paper describes a new approach for non-destructive testing of the structural and geometric parameters of dielectric objects using capacitance techniques. The novelty of this approach lies in the design of a capacitance sensor comprising an array of electrodes with changeable potential distribution on them during a measurement process. This makes solvable the problem of measuring independently three input parameters. To demonstrate the capabilities of the developed measurement algorithms, the case studies based on computer simulation have been carried out. [ABSTRACT FROM AUTHOR]

Independently controlled irrigation plots were designed to test two container nursery irrigation regimes on oakleaf hydrangea ( Hydrangea quercifolia ‘Alice’) in both nursery and controlled greenhouse environments. The experiments were conducted in both 3.8 and 11.4 L containers. Plants were automatically irrigated by one of two soil moisture sensor-based regimes: (1) a daily water use (DWU) system that delivered the exact amount of water that had been lost in the previous 24 h and (2) an on-demand (OD) irrigation system based on a specific substrate moisture content derived from the relationship between substrate moisture and photosynthetic rate. In this system, irrigation was applied when the substrate moisture level fell below 33% container capacity, which corresponded to 90% maximum predicted photosynthetic rate. Both treatments delivered the volume of water required to return the containers to container capacity by overhead irrigation, but the DWU system was static, irrigating once per day, whereas OD was dynamic and irrigated whenever the substrate moisture reached the 33% threshold level. Gas exchange was measured at the driest point prior to the next irrigation event. Periodical growth index, water use, and final dry weight were recorded. OD used less water than DWU outdoors, reduced leaching fraction among greenhouse experiments, and had either no or a positive impact on biomass in all but one trial. For 3.8 L plants, photosynthesis and stomatal conductance were consistently greater when irrigated by the OD program. Both treatments used significantly less water than the industry standard of 2.5 cm per day. This research demonstrated that both DWU and OD are a dramatic improvement over conventional irrigation scheduling and could be adopted as conservative irrigation systems for nursery production. [ABSTRACT FROM AUTHOR]

Highlights: [•] We tested the continuous-time monitoring of LWC using EnviroSMART® sensors. [•] Eight capacitance sensors and two time-domain reflectrometers were used. [•] Field results were validated by means of laboratory tests and a FEM model. [•] The study demonstrates that capacitance sensors are sensitive to LWC. [•] Their installation entails localized melting and air intrusion around the tube. [ABSTRACT FROM AUTHOR]

Electrical capacitance volume tomography (ECVT) has shown to be an effective low-cost and high-speed imaging technique suitable for many applications, including 3-D reconstruction of multiphase flow systems. In this paper, we introduce the concept of adaptive ECVT based upon the combination of a large number of small individual sensor segments to comprise synthetic capacitance plates of different (and possibly noncontiguous) shapes while still satisfying a minimum plate area criterion set by a given SNR. The response from different segments is combined electronically in a reconfigurable fashion. The proposed adaptive concept paves the way for ECVT to be applicable in scenarios requiring higher resolution and dynamic imaging reconstruction. [ABSTRACT FROM PUBLISHER]

Several newly developed sensors based on capacitance and frequency techniques have simplified real-time determination of soil water content (θ). The 10HS sensor is one of the most recent developments in capacitance sensors. However, up to now, little is known about the accuracy of this sensor, and the dependency of its measurements on soil type and environmental factors. In this study, the performance of the 10HS sensor was investigated through experiments using liquids with known dielectric properties and experiments in a set of porous media exhibiting a wide range of properties. The response of the 10HS sensor in bilayered systems was also investigated. The experimental results suggested that there is a distinct instrument sensitivity to soil type, indicating the need for individual soil calibration. A set of specific calibration equations for the various porous materials studied were proposed. It was shown that the 10HS sensor is able to provide reasonably accurate relative permittivity (εr) measurements, but the manufacturer’s εr calibration equation, to some extent, overestimates εr in the full range of the measured values in liquids. The sensor to sensor variability was also found to be relatively small. It was shown that the manufacturer’s calibration equation for measuring θ Version 1 underestimates θ, whereas Version 3 overestimates θ, in all porous materials examined. The most accurate results were provided by the proposed soil-specific calibration equations obtained using the multipoint calibration equations. However, the two-point calibration equations reasonably represent θ in all porous media tested. Underestimation of soil moisture with increasing temperature in coarse porous media and overestimation in fine porous media were observed. The temperature dependence was more important in the fine porous media. The effect of electrical conductivities in sand was also examined, and it was found to be negligible. Finally, the sensors’ response in bilayered systems generally follows the refractive averaging scheme at lower εr values and the arithmetic averaging scheme at higher εr values. [ABSTRACT FROM AUTHOR]

More efficient irrigation practices are needed in ornamental plant production to reduce the amount of water used for production as well as runoff of fertilizers and pesticides. The objective of this study was to determine how different substrate volumetric water contents (θ) affected petunia (Petunia xhybrida) growth and to quantify the daily water use of the plants. A soil moisture sensor-controlled irrigation system was used to maintain θ within ≈0.02 m3 ⋅ m-3 of the θ threshold values for irrigation, which ranged from 0.05 to 0.40 m3 ⋅ m-3. Shoot dry weight increased as the θ threshold increased from 0.05 to 0.25 m3 ⋅ m-3 and was correlated with the total amount of irrigation water applied over the 3-week course of the experiment. The daily water use of the petunias grown with a θ threshold of 0.40 m3 ⋅ m-3 was 12 to 44 mL/plant and was positively correlated with both plant age and daily light integral. Lower θ thresholds resulted in a decrease in both leaf water (ψ) and osmotic potential (ψS). A decrease in turgor pressure (P) at lower θ was seen at 11, but not 20 days after the start of the treatments. There were no significant effects of θ on ψ, ψS, or P on fully rehydrated plants at the end of the study. Plants were able to survive and grow at all θs, although water at a θ less than 0.20 m3 ⋅ m-3 is generally considered to be unavailable to the plants. Results show that it is possible to automatically irrigate plants with the use of soil moisture sensors, and this approach to irrigation may have applications in controlling the growth of ornamental plants. [ABSTRACT FROM AUTHOR]

Abstract: Our prototype atomic force microscope (AFM) uses a piezoelectric tube to scan a probe tip over a sample surface, while a PC-based digital controller maintains a constant tip–sample separation based on feedback from a quartz tuning fork proximity sensor. We have successfully run the AFM in both the shear and tapping modes, using optical fibers as probe tips. The AFM utilizes a set of capacitance sensors with a spherical target for direct measurement of probe tip displacements. We have used this system to image localized surface topography of a square wave silicon calibration grating with localized step height accuracy of 1nm in the vertical direction and vertical RMS noise less than 4nm. The lateral accuracy is on the order of 100nm, and our largest lateral measurement scans have been performed on regions with step heights of 26.5nm and a modest scan speed of . [Copyright &y& Elsevier]

Efficient water resource management is one of the most important policy issues facing agriculture in Hawaii in the years ahead. Soil water sensors, multisensor capacitance probes (MCP), have been successfully used for different water management projects. These MCPs monitor water content at multiple depths and at various locations in real-time. The objectives of this study were to determine the effect of water content on field soil bulk density of Wahiawa silty clay tropical soil; measure field saturated hydraulic conductivity of this tropical soil; calibrate MCP system for this soil; and monitor and evaluate real-time soil water content variations under a tomato crop using the calibrated MCP system. Sensor calibration was conducted under laboratory conditions. Soil bulk density at different water contents and saturated hydraulic conductivity were measured on the field. Bulk density increased with increasing water content; there was a 30 percent bulk density increase as a result of 0.25 cm³ cm-3 water content variation. Compared with the manufacturer's calibration, site specific laboratory calibration of MCP gave a more accurate determination of soil water. Field determined saturated hydraulic conductivity was higher than laboratory determined values reported in the literature for the same soil type. Real-time soil water content monitoring within the root zone showed substantial variations due to water input (irrigation and rainfall) and water output (evapotranspiration and deep percolations). However, water content variations were much further reduced in the soil layer below the root zone. [ABSTRACT FROM AUTHOR]

The design methodology of capacitance sensors for void-fraction measurement in adiabatic two-phase flow systems is presented in this paper. The effect of design parameters on the capacitance output has been theoretically and experimentally investigated for two types of sensor configurations: concave and ring types. Experiments were performed using air-oil two-phase flow to determine the signal-to-noise ratio, sensitivity, and time response of the capacitance sensors. The results show that the ring-type sensors are more sensitive to the void-fraction signal than the concave type for the same spatial resolution. The predictions from the theoretical model for the ring-type sensors are in better agreement with the experimental results than for the concave type. The mean value, time trace, power spectral density (PSD), and the probability density function (PDF) of the void-fraction signal from the capacitance sensors are used to objectively identify the flow pattern. The method was validated using high-speed video images of the flow and comparing the results to those from the signal analysis [ABSTRACT FROM PUBLISHER]

Abstract: The interpretation of soil water dynamics under drip irrigation systems is relevant for crop production as well as on water use and management. In this study a three-dimensional representation of the flow of water under drip irrigation is presented. The work includes analysis of the water balance at point scale as well as area-average, exploring uncertainties in water balance estimations depending on the number of locations sampled. The water flow was monitored by detailed profile water content measurements before irrigation, after irrigation and 24h later with a dense array of soil moisture access tubes radially distributed around selected drippers. The objective was to develop a methodology that could be used on selected occasions to obtain ‘snap shots’ of the detailed three-dimensional patterns of soil moisture. Such patterns are likely to be very complex, as spatial variability will be induced for a number of reasons, such as strong horizontal gradients in soil moisture, variations between individual sources in the amount of water applied and spatial variability is soil hydraulic properties. Results are compared with a widely used numerical model, Hydrus-2D. The observed dynamic of the water content distribution is in good agreement with model simulations, although some discrepancies concerning the horizontal distribution of the irrigation bulb are noted due to soil heterogeneity. [Copyright &y& Elsevier]

Simulation and optimization were applied to a capacitive sensor system based on electrical tomography technology. Sensors, consisting of Morgantown Energy Technology Center (METC) axial synchro driving guard electrodes and two sets of detecting electrodes, make it possible to obtain simultaneously two groups of signals of the void fraction in oil-gas two-phase flow. The computational and experimental results showed that available sensors, charactered by high resolution and fast real-time response can be used for real-time liquid-gas two-phase flow pattern determination. [ABSTRACT FROM AUTHOR]

Multimodality sensing is used for monitoring of multiphase hydrocarbon flow where there is a need to measure the quantity of oil, water and gas in a cross section of a pipe originating from an oil well. Information on the flow regime, i.e., the physical distribution of the hydrocarbon production constituents in the pipe cross section, is demanded. Expedient information concerning the productivity of the well, i.e., the quantity of oil, water and gas produced, the transport of multiphase flow and the upstream separation process can be provided by tomographic information. A dual modality tomograph (DMT), consisting of capacitance and gamma-ray sensors, has been developed at the University of Bergen. Characterization of the DMT has demonstrated feasibility in relation to the hydrocarbon flow application, but also shortcomings mainly relating to the performance of the capacitance sensor in water continuous phase, and the salinity dependence of the gamma-ray measurements. Research work has been conducted to further develop the DMT for hydrocarbon multiphase flow. The new developments include dual modality densitometry (DMD), where both mixture density and salinity are measured, and a water-cut independent high-frequency magnetic field sensor. [ABSTRACT FROM PUBLISHER]

Abstract: Measurements of suspended sediment concentration are of importance in soil erosion research and soil and water conservation practices and monitoring. A method of measuring sediment concentration with capacitance sensors was advanced in this study. The relationships between the sediment concentration in flowing water and the output of capacitance sensor, as affected by temperature, flow velocity, soil types and salt contents were experimentally investigated with two types of capacitance sensors. The temperature used in the experiments ranged from 0 to 40 degrees centigrade. Salt concentrations (NaCl) in the flowing water ranged from 0 to 5 g/L and the flow velocity varied between 0.5 to 2.0 m/s. Two types of soil (a loam and a sandy soil) with sediment concentration up to 70% were studied. The results showed that suspended sediment concentrations, over a wide range, were linearly correlated with the outputs of capacitance sensors. The outputs of the capacitance sensor increased with temperature, with little influence from flow velocity, soil types and salt concentration. The results suggest that capacitance sensors may be used for sediment concentration measurement of flowing water. [Copyright &y& Elsevier]

Most citrus nurseries in Florida, USA use overhead irrigation, but subirrigation methods, including ebb-and-flow and capillary mats, have been shown to conserve water and accelerate plant growth relative to overhead irrigation for other nursery species and may be a viable alternative to overhead irrigation in citrus liner production. The objectives of this study were to (1) automate an ebb-and-flow system for citrus liner production using capacitance sensors, and (2) evaluate how subirrigation and overhead irrigation methods affect water use, plant growth parameters, and substrate chemical properties. A study was conducted from 22 May to 23 September 2018 in which liners of six commercially important rootstock cultivars in cone-shaped containers were subjected to one of the following irrigation methods: ebb-and-flow triggered at substrate volumetric water contents (θ) of 0.24, 0.36, or 0.48 m3 m−3, capillary mats, and overhead irrigation. Capacitance sensors successfully monitored irrigation throughout the study. Ebb-and-flow benches used substantially less water (~411 L) than either capillary mats (13,098 L) or overhead irrigation (3193 L). By the end of the study, rootstock cultivars propagated using subirrigation methods were approximately 22% taller with 7% more total biomass than plants subjected to overhead irrigation. Additionally, plant growth at the 0.24 m3 m−3 threshold used to trigger ebb-and-flow was as great or greater than growth at 0.36 and 0.48 m3 m−3 thresholds. During the final five weeks of the study, substrate electrical conductivity was higher using subirrigation methods (0.84–1.3 ds m−1) than under overhead irrigation (0.55–0.8 ds m−1), but there were no symptoms of salt stress observed in plants at any time. Results from this study show that ebb-and-flow is a viable alternative to overhead irrigation and is superior to capillary mats for water conservation. In automated ebb-and-flow systems in Florida, we recommend using the 0.24 m3 m−3 threshold to produce the citrus rootstock cultivars used in this study with peat: perlite substrate. • Ebb-and-flow subirrigation was successfully automated for citrus liner production. • Ebb-and-flow benches used less water than capillary mats and overhead irrigation. • Liners under overhead irrigation generally grew slower than under subirrigation. • Triggering irrigation at 0.24 m3 m−3 substrate threshold optimized liner growth. • Ebb-and-flow is a viable alternative to overhead irrigation for liner production. [ABSTRACT FROM AUTHOR]