Abstract: In electrical capacitance tomography, capacitance changes are used to determine the permittivity distribution in the imaging area. However, the changes are small compared with the standing capacitances, e.g., usually in the order of 10%–30%. For a single channel capacitance sensor, a differential configuration having a redundant pair of electrodes can be used to cancel the standing capacitance. However, there has been no report so far introducing such differential configuration into electrical capacitance tomography (ECT) sensors. This is mainly due to the fact that an ECT sensor is composed of an array of electrodes, e.g., 8, 12, and 16 and the capacitance measurements in ECT are required to interrogate capacitances of all electrode pair combinations, which introduce significant difficulty for a differential configuration. In this paper, a novel differential ECT sensor is proposed and designed, which consists of concentrically arranged dual array electrodes. It can also be thought as an additional array of electrodes being inserted between the measuring electrodes and the outer screen of a conventional ECT sensor. The new sensor design has been validated by the numerical simulation. A prototype sensor has been developed and evaluated with an field programmable gate arrays (FPGA)-based ECT measurement system, showing that with the proposed differential sensor, the dynamic range of the measured capacitance is reduced by $\sim 80$ % and an average improvement of 10.8 dB in signal-to-noise ratio is achieved.

Abstract: The performance of the Irrometer 200SS Watermark granular matrix sensor (WM), John Deere Field Connect (JD-v2) probe, and Delta-T PR1-capacitance (PR1-C) probe were evaluated against a Troxler 4302 neutron gauge (NG) for in-season field volumetric water content (θv) measurements at two soil depths in a Hastings silt loam soil at the University of Nebraska-Lincoln/Institute of Agriculture and Natural Resources South Central Agricultural Laboratory (SCAL) near Clay Center, Nebraska. The performances of the sensors were investigated over three years (2011-2013) under various water, nutrient, and crop management practices. The WM sensors performed best when using a field-calibrated soil water retention curve (SWRC) [root mean square difference (RMSD) = 0.024 m3 m-3] as compared to a SWRC developed from a pedotransfer function (RMSD = 0.070 m3 m-3). The WM sensors using a previously developed SWRC for the experimental field resulted in RMSD values less than 0.05 m3 m-3 when compared to the NG-measured θv at all depths and years. The JD-v2 probes underestimated θv in the dry range and overestimated θv in the wet range, which resulted in regression slopes and intercepts for the 0.30 and 1.0 m soil depths that were significantly different from unity (i.e., 1.0) and zero (p0.05

Abstract: Room temperature liquid-metal microfluidic devices are attractive systems for hyperelastic strain sensing. These liquid-phase electronics are intrinsically soft and retain their functionality even when stretched to several times their original length. Currently two types of liquid metal-based strain sensors exist for in-plane measurements: single-microchannel resistive and two-microchannel capacitive devices. With a winding serpentine channel geometry, these sensors typically have a footprint of about a square centimeter. This large footprint of an individual device limits the number of sensors that can be embedded into, for example, electronic fabric or skin. In this work we introduce an alternative capacitor design consisting of two liquid metal electrodes separated by a liquid dielectric material within a single straight channel. Using a liquid insulator instead of a solid elastomer enables us to tailor the system's capacitance by selecting high or low dielectric constant liquids. We quantify the effects of the electrode geometry including the diameter, spacing, and meniscus shape as well as the dielectric constant of the insulating liquid on the overall system's capacitance. We also develop a procedure for fabricating the two-liquid capacitor within a single straight polydiemethylsiloxane channel and demonstrate that this device can have about 25 times higher capacitance per sensor's base area when compared to two-channel liquid metal capacitors. Lastly, we characterize the response of this compact device to strain and identify operational issues arising from complex hydrodynamics near liquid-liquid and liquid-elastomer interfaces.

Abstract: A non-contact capacitance type liquid-level transducer for a conducting liquid consists of a short circuited non-inductive coil wound on a uniform cylinder made of insulating material, such as glass, PVC, nylon, and teflon. The cylinder is connected with a storage tank through a metallic connector and the capacitance between upper short circuited end of the coil and metallic connector varies linearly with liquid level measured from datum level. The capacitance at datum level depends on atmospheric condition and the fringe effect of other conductors. So, the transducers require frequent recalibration depending on atmospheric and environmental conditions. In the present paper, this non-contact capacitive sensor has been further modified in order to minimize this defect of non-contact capacitive sensor. Furthermore, all the conventional capacitance type-level sensors are associated with a perpendicular plate capacitance between liquid and electrode, which varies with the length of the electrode. In this paper, the effect of this perpendicular capacitor on liquid level measured has been studied and its effect is minimized. The proposed modified transducer has been designed and developed and its theory of operation has been derived. The performance of the developed transducer has been experimentally studied and the experimental results are reported in the paper. A good linear performance characteristic of the transducer with very minimum parasitic capacitance effect has been observed.

Abstract: Closed-form expressions of the parasitic insulator capacitance and the substrate capacitance for tapered through-silicon vias (T-TSVs) are proposed. The expressions are suitable for TSVs with high aspect ratio (thin and long). The maximum percentage errors between the calculated and simulated results for the insulator capacitance and the substrate capacitance are 1.86% and 3.75%, respectively. Then the equivalent circuit model of the T-TSV signal-ground pair is established and validated by comparison with the full-wave simulation results. Furthermore, the electrical characteristics of the T-TSV are evaluated with the proposed expressions. The results indicate that the T-TSV has longer latency and less crosstalk than the cylindrical TSVs.

Abstract: The online and continuous measurement of velocity, concentration and mass flow rate of pneumatically conveyed solid particles for the high-efficiency utilization of energy and raw materials has become increasingly significant. In this paper, an integrated instrumentation system for the velocity, concentration and mass flow rate measurement of dense phase pneumatically conveyed solid particles based on electrostatic and capacitance sensorsis developed. The electrostatic sensors are used for particle mean velocity measurement in combination with the cross-correlation technique, while the capacitance sensor with helical surface-plate electrodes, which has relatively homogeneous sensitivity distribution, is employed for the measurement of particle concentration and its capacitance is measured by an electrostatic-immune AC-based circuit. The solid mass flow rate can be further calculated from the measured velocity and concentration. The developed instrumentation system for velocity and concentration measurement is verified and calibrated on a pulley rig and through static experiments, respectively. Finally the system is evaluated with glass beads on a gravity-fed rig. The experimental results demonstrate that the system is capable of the accurate solid mass flow rate measurement, and the relative error is within −3%–8% for glass bead mass flow rates ranging from 0.13 kg/s to 0.9 kg/s.

Abstract: A novel semiconductor variable capacitor is presented. The semiconductor structure is simple and is based on a semiconductor variable MOS capacitor structure suitable for integrated circuits, which has at least three terminals, one of which is used to modulate the equivalent capacitor area of the MOS structure by increasing or decreasing its DC voltage with respect to another terminal of the device, in order to change the capacitance over a wide ranges of values. Furthermore, the present invention decouples the AC signal and the DC control voltage minimizing the distortion and increasing the performance of the device, such as its control characteristic. The present invention is simple and only slightly dependent on the variations due to the fabrication process. It exhibits a high value of capacitance density and, if opportunely implemented, shows a quasi linear dependence of the capacitance value with respect to the voltage of its control terminal.

Abstract: Soil moisture variability has a major impact on runoff generation. In this study, the dynamics and variability of soil moisture at small hillslope transects were analyzed by artificial rainfall simulation experiments in which the influence of crop type and slope angle were considered. Soil moisture variability and dynamics during the rainfall-runoff process were monitored by capacitance sensors (EC-5) with high temporal resolution (1 min) and continuously measured after rainfall ceased to investigate soil moisture dynamics and patterns by the method of data visualization. Relationships between soil moisture and runoff (surface and subsurface flow) and response lag times of soil moisture at different slope positions and soil layers were investigated. The dynamics of soil moisture during the entire crop growth stage were also analyzed. Results showed that soil moisture exerted strong influence on runoff generation, but the relationships were strongly affected by crop type. There was an obvious thres...

Abstract: An imaging system includes an array of photodetectors and electronic circuitry associated with the photodetectors to read intensity values from the photodetectors. The electronic circuitry can include an integrator with an integrator capacitor having a nominal capacitance, wherein a gain of the electronic circuitry associated with a photodetector can depend at least in part on the actual capacitance of the integrator capacitor, the actual capacitance differing from the nominal capacitance. The imaging system can be configured to determine a gain factor that depends at least in part on the actual capacitance and/or a signal voltage input to the integrator. The imaging system can be configured to apply the gain factor based at least in part on the actual capacitance of the integrator capacitor calculated. The imaging system can be a thermal imaging system and may include an infrared camera core.

Abstract: Various methods and systems for the use of capacitance sensors 76 within medical devices 12 configured for patient monitoring are provided. The capacitance sensors 76 are configured to measure a change in capacitance resulting from a material (e.g., human tissue, water, gel, cloth, etc.) placed near (e.g., close proximity to) the medical device 12 and/or resulting from a material making physical contact with the medical device 12. In certain embodiments, the capacitance sensor 76 may be utilized to detect whether one or more portions of the medical sensor 12 are securely applied to the patient's tissue (e.g., sensor "on") and/or may be utilized to detect whether one or more portions of the medical sensor 12 fail to maintain secure contact with the patient's tissue (e.g., sensor "off"). Further, in certain embodiments, the capacitance sensor 76 may be utilized to distinguish between one or more types of materials (e.g., human tissue, water-based materials, etc.).

Abstract: In this paper, we present a suitable electrode design for capacitive sensor for low-cost soil moisture profile probes. The probe can be implemented in quite low cost because it only requires single-side conductive patterns on PET film. Although inter-digital capacitor (IDC) is commonly used for coplanar capacitive sensor since it can sense wider area with sufficient accuracy, particularly for profile probe, narrower sensing area is preferred in order to observe capacitance on each depth. Coplanar plate capacitor (CPC) can focus on soil moisture on each profile level thanks to its single gap design so we conclude the CPC should be suitable for profile probes. We confirmed that CPC has almost identical or even better performance compared to IDC. In addition to that, CPC has an advantage that it has less sensitivity degradation with thick protective coating than IDC.

Abstract: A high capacitance embedded capacitor and associated fabrication processes are disclosed for fabricating a capacitor stack in a multi-layer stack to include a first capacitor plate conductor formed with a cylinder-shaped storage node electrode formed in the multi-layer stack, a capacitor dielectric layer surrounding the cylinder-shaped storage node electrode, and a second capacitor plate conductor formed from a conductive layer in the multi-layer stack that is sandwiched between a bottom and top dielectric layer, where the cylinder-shaped storage node electrode is surrounded by and extends through the conductive layer.

Abstract: To test a theory of the recently discovered phenomenon of super dielectric behavior at very low frequency, the dielectric constants of several ‘pastes’, composed of porous alumina powders filled to the point of incipient wetness with water containing dissolved sodium chloride, were measured. The effective dielectric low frequency constants of some of the pastes were greater than 1010, dramatically higher than that of any material ever reported. Moreover, the total energy density reported for one capacitor generated with NaCl-based super dielectric material is marginally higher than found in any prior report. These results are consistent with this recently postulated model of low frequency super dielectric behavior in porous, non-conductive materials saturated with ion-containing liquids: upon the application of an electric field, ions dissolved in the saturating liquid contained in the pores will travel to the ends of pore-filling liquid droplets creating giant dipoles. The fields of these giant dipoles oppose the applied field, reducing the net field created per unit of charge on the capacitor plates, effectively increasing charge/voltage ratio, hence capacitance. This is simply a version of the theory of ‘polarizable media’ found in most classic texts on electromagnetism. Other observations reported here include (1) the impact of ion concentration on dielectric values, (2) a maximum voltage similar to that associated with the electrical breakdown of water, (3) the loss of capacitance upon drying, (4) the recovery of capacitance upon the addition of water to a dry super dielectric material, and (5) the linear relationship between capacitance and inverse thickness. All observations are consistent with the earlier proposed model of the super dielectric phenomenon. An extrapolation of results suggests this technology can lead to energy density greater than the best lithium-ion battery.

Abstract: In this article, the design of a low-cost educational liquid-level sensor circuit is described. The sensor is of capacitive type and is in the form of a parallel plate capacitor made up of two alum...

Abstract: A device includes a glass substrate and a capacitor. The capacitor includes a first metal coupled to a first electrode, a dielectric structure, and a via structure comprising a second electrode of the capacitor. The first metal structure is separated from the via structure by the dielectric structure.

Abstract: A capacitor charging-discharging system, including a plurality of serially connected capacitors, a voltage source for setting an equalization potential, and a plurality of parallel monitoring circuit. Each parallel monitoring circuit is connected to the two ends electrodes of one capacitor, and includes: a voltage dividing circuit configured to resistively divide and attenuate two voltages respectively on the two end electrodes of the one capacitor, a differential amplifier configured to amplify a difference between the two divided voltages to thereby detecting a charge potential of the one capacitor, a comparator configured to compare the charge potential with the equalization potential, and a charge current bypass circuit configured to control charge current of the one capacitor, based on an output of the comparator, so that the charge potential of the one capacitor matches the equalization potential.

Abstract: This paper presents a passive LC wireless sensor for measuring temperature. The sensor is designed as a parallel connection of a spiral inductor and an interdigitated capacitor and it was fabricated in a conductive layer using LTCC (Low Temperature Co-fired Ceramic) technology. The inderdigitated capacitor electrodes were coated with a thin film of bismuth doped barium titanate (Ba0.9Bi0.066TiO3), whose permittivity changes with temperature, which directly induces changes in the capacitance of the interdigitated capacitor and consequently changes the resonant frequency of the sensor. The measurements of S-parameter of the sensor were performed using a Vector Network Analyzer (E5071B, Agilent Technologies, Santa Clara, CA, USA), whose port was connected to the antenna coil that was placed around the sensor in order to be able to wirelessly detect temperature, in the temperature range from 25 °C to 165 °C.

Abstract: The primary application of this work is to design and develop a reliable capacitance sensing system for measuring very small capacitive changes at low frequencies for human interface application. The sensing system is applicable in monitoring and characterizing human body movement. The interface circuit measures very small capacitive variation. A number of capacitive values have been set in the proposed system and the produced capacitance variations have been measured for verifying the possibility to characterize the presence/absence of human bodies. A variation in capacitance results in variation on the output voltage. Based on change in the voltage conclusion can be made regarding the presence/absence state of the human body. The sensing method is based on the fundamental principle of capacitance changes that is produced by the interaction of a human body with capacitive sensors. Different human body will exhibit different capacitance due to their height, weight and so on; giving each person distinctive identification. Primary simulation results show that the measurement of little capacitance variation using an interface circuit is precise and linear. The simulation results conclude that a very small capacitive variation can be detected using the developed capacitive sensing method. When a human body enters in the vicinity area right above the sensor, a variation in capacitance as well as output voltage can be observed.

Abstract: An insulation detecting device includes a flying capacitor that holds a charged voltage, and a measurement and calculation unit that measures the charged voltage of the flying capacitor and calculates a ground fault resistance formed between a direct-current power supply electrically insulated from a ground, and the ground, based on the measured voltage. The flying capacitor includes one or a plurality of first capacitors, one or a plurality of second capacitors connected with the first capacitor in parallel, and a parallel cancellation switch arranged between the first capacitor and the second capacitor, and which performs parallel connection, and cancellation of the parallel connection, between the first capacitor and the second capacitor. A capacitance of the flying capacitor is variably changed by turning on or turning off of the parallel cancellation switch.

Abstract: A capacitance-to-digital converter (CDC) that gives a digital value proportional to the change in the capacitance of a sensor, independent of its nominal capacitance, is presented in this paper. The CDC presented is suitable for single element capacitive sensors. For most of the CDCs, available in the market, the output depends on the nominal value of the sensor. Thus, a manual intervention for appropriate correction in the output is required whenever a new sensor is connected to such CDCs. The proposed CDC uses a simple automatic calibration, employing a digitally controlled reference voltage in a feedback topology, and provides an output independent of the nominal value of the sensor employed. This automatic calibration also removes the dependence on the accuracy of the absolute value of reference capacitor, in the final output. The proposed CDC is based on a switched-capacitor dual-slope technique and possesses the advantages of the dual-slope conversion method. A prototype CDC has been developed and the test results are presented. The results obtained show that the output of the proposed converter is not a function of the nominal capacitance of the sensor for a wide range (50 pF to 1.15 nF). For this range, the worst error noted from the prototype CDC was less than 0.65 %.

Abstract: A device for detecting steering wheel contact comprises at least a first electrode (12) which is provided in a steering wheel (10) and which forms, together with a human body acting as a second electrode and a dielectric situated therebetween, at least one sensor capacitor (26). The device also comprises an evaluation circuit (24) having a reference capacitor (30) of known capacitance which can be connected parallel to the sensor capacitor (26), a direct current voltage source (34) which can be connected to the reference capacitor (30), and a measuring device for measuring the voltage at the reference capacitor (30). A method for detecting steering wheel contact using such a device comprises the following successive steps: charging the reference capacitor (30) by applying a known reference voltage, or charging the reference capacitor (30) and subsequently measuring a first voltage at the reference capacitor (30); connecting, in parallel, the sensor capacitor (26) to the reference capacitor (30) so that a portion of the charge of the reference capacitor (30) is transmitted to the sensor capacitor (26); measuring a second voltage at the reference capacitor (30); and determining the capacitance of the sensor capacitor (26) from the known capacitance of the reference capacitor (30), the reference voltage or the first voltage and the second voltage.

Abstract: An electrical circuit comprising at least two negative capacitance insulators connected in series, one of the two negative capacitance insulators is biased to generate a negative capacitance. One of the negative capacitance insulators may include an air-gap which is part of a nanoelectromechnical system (NEMS) device and the second negative capacitance insulator includes a ferroelectric material. Both of the negative capacitance insulators may be located between the channel and gate of a field effect transistor. The NEMS device may include a movable electrode, a dielectric and a fixed electrode and arranged so that the movable electrode is attached to at least two points and spaced apart from the dielectric and fixed electrode, and the ferroelectric capacitor is electrically connected to either of the electrodes.

Abstract: A simple relationship determining the dielectric constant of a material inserted in a parallel-plate capacitor is formulated from Gauss's law for a uniform electric field and the continuity condition of electric flux at the boundary of the material The relationship suggests that the dielectric constant can be determined from the dependence of the charge stored on the capacitor on the thicknesses of the material and the air layer between the plates A uniform field is created by applying an ac voltage to the plates, which includes a guard ring The stored charge is estimated by using an oscilloscope to measure the voltage across a resistor inserted between the power supply and the capacitor The results of the measurement are given for planar materials such as soda-lime glass, Bakelite, acrylic glass, and Teflon with a thickness of 05–1 cm

Abstract: A sensor concept is developed and analyzed for in situ characterization of a thin dielectric layer. An array of long, planar electrodes is flush-mounted into opposing faces of two substrates on either side of the dielectric layer. The substrates are oriented such that the lengthwise dimensions of the opposing electrodes are orthogonal. Capacitance is measured between single electrode pairs on opposite substrates while all other electrodes are grounded. The electric field between the active electrodes is sharply focused at their crossing point, resulting in high sensitivity to void content in a square detection zone of the dielectric layer. For a fixed interfacial gap size, direct proportionality of the capacitance with void fraction within the detection zone is poor for high electrode-to-electrode spacing on the substrates, but improves dramatically as this spacing is reduced. Three methods of deriving a simulation-based sensitivity response of measured capacitance to any arbitrary two-dimensional void geometry are investigated. The best method requires data from simulations of an empty air gap and a TIM-filled gap, and uses a reduced-order superposition technique to predict the normalized capacitance value obtained for any void geometry to within 10% of that predicted by a high-fidelity direct simulation. The sensing technique is demonstrated using manually introduced voids of 250 µm–2000 µm diameter in a 254 µm thick interface material layer with a dielectric constant of 4.7. The relationship of the capacitance to the void fraction is shown to fall within the predicted bounds.

Abstract: The Hilhorst model was used to convert bulk electrical conductivity (σb) to pore water electrical conductivity (σp) under laboratory conditions by using the linear relationship between the soil dielectric constant (eb) and σb. In the present study, applying the linear relationship eb–σb to data obtained from field capacitance sensors resulted in strong positive autocorrelations between the residuals of that regression. We were able to derive an accurate offset of the relationship eb–σb and to estimate the evolution of σp over time by including a stochastic component to the linear model, rearranging it to a time-varying dynamic linear model (DLM), and using Kalman filtering and smoothing. The offset proved to vary for each depth in the same soil profile. A reason for this might be the changes in soil temperature along the soil profile. Editor D. Koutsoyiannis; Associate editor M.D. Fidelibus

Abstract: In order to increase two important factors of capacitance and self-resonant frequency (SRF) of the microelectromechanical systems (MEMS)-switched capacitor, we developed a room-temperature-grown high- $\kappa $ TiO2 dielectric layer in the metal–insulator–metal (MIM) capacitor and an SU-8 bridged beam structure in the MEMS switch. The high- $\kappa $ TiO2 dielectric layer, which has a relative dielectric constant of up to 32, was utilized to minimize the MIM capacitors’ sizes while maintaining their high capacitance values. In addition, the SU-8 bridged beam structure of the MEMS switch, whose radio frequency (RF) signal interconnecting part is electrically isolated from the switching mechanism, was introduced to shorten the RF signal path. Because of the high- $\kappa $ dielectric and the bridged beam structure, we have achieved a very high capacitance of up to 14.3 pF with an SRF of 1.8 GHz (the MIM capacitor size was $50~\mu $ m $\times 1200~\mu $ m). The same-sized MIM capacitor with a conventional Si3N4 dielectric layer and a conventional cantilever beam-switched capacitor showed only 4.9 pF with an SRF of 2.8 GHz. In a similar capacitance value, the proposed switched capacitor showed 22% increase in SRF (7.1 GHz at 0.92 pF) compared with the conventional cantilever beam switched capacitor with a Si3N4 dielectric layer (5.8 GHz at 1.01 pF). The high SRF was attributed to the short RF signal path and the minimized capacitor size, thereby reducing parasitic inductance. [2014-0130]