Capacitance Characteristics of Glass-Embedded Interdigitated Capacitors for Touch Sensing Applications

This article presents the design and implementation of a precision lock-in amplifier for universal capacitive sensing. While conventional capacitive transimpedance amplifier (C-TIA) based on lock-in detection can extract subtle capacitance changes from a noisy environment, the capacitance resolution is further limited by parasitic capacitance at the input node, the baseline capacitance of the sensor, and current noise introduced by input bias resistor. To address these limitations, this work proposes a zeptofarad (zF) resolution lock-in amplifier using three key techniques: 1) a self-calibrated negative capacitor (NC) to cancel the parasitic capacitance at C-TIA input; 2) baseline capacitance compensation to improve the dynamic range (DR), allowing the use of higher excitation voltages, thereby improving the SNR; and 3) multi-element pseudo-resistor (PR) to mitigate shot noise in the presence of elevated input dc current. The proposed lock-in amplifier was implemented in a standard 180-nm CMOS process, achieving a best-in-class resolution of 2.06 zF<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${}_{\mathbf {rms}}$ </tex-math></inline-formula> (BW = 10 Hz) while tolerating a maximum input dc current of 122 nA. This amplifier enables wideband lock-in detection from 1 kHz to 62 MHz. Both parasitic and baseline capacitance can be automatically calibrated in the foreground, considerably improving the speed and practicality of the measurement.

In rock climbing, an appropriate motor preparation to a given climbing hold(s) is crucial for a fluent climbing. We investigated the influence of visual-tactile information in motor preparation of climbing, particularly the effect of the number of the holds and the tactile input of an actual hold was examined. Reaction times (RTs) under the priming paradigm were compared for climbers and non-climbers. Participants were asked to respond to a visual target (left or right arrow) after the presentation of a picture of a single climbing hold (Single-Prime condition: SP) or two holds (Double-Prime condition: DP). Before commencing each trial block, the participants were also asked to touch or watch an actual hold (touch /no-touch condition). The response based on the congruity between the orientation of the hold and that of the arrow was categorised as either congruent or incongruent. An ANOVA performed on the RTs showed the congruency effect, but this was observed only in the non-climbers. An additional analysis revealed a marginally significant climbing experience-related interaction. In the high-experienced climbers, the RTs in the touch condition were slower than those in the no-touch condition but this was only in the SP condition. In the no-touch condition, the RTs of DP were slower than those of SP. These results therefore suggest that the motor preparation is mediated by visual and tactile inputs of a given hold. The time needed for motor preparation, particularly in highly experienced climbers, may be modulated by the representational complexity of climbing movements through tactile information. Highlight The number of the holds visually presented affected the motor preparation. The tactile input of the climbing hold modulated the motor preparation only in the highly experienced climbers. Our findings imply that climbing-specific context (i.e. combination of the given holds) and experience (i.e. action competency) are involved in the motor preparation of climbing.

Inter digital capacitive (IDC) sensor is useful in numerous applications. In this work, a prototype of a comb IDC sensor is developed using the PCB fabrication technique to study the effect of frequency during water head transition. The mathematical and graphical analysis of the work is based on the collected real-time data. A statistical tool Pearson's are justifying the linearity of the sensor. The statistical result of Pearson's r values (> 0.9924) illustrates a strong positive correlation between the two variables, capacitance, and water level. It is found that the IDC sensor has good linearity with the water level transition for the 0.5 kHz to 40 kHz frequency range.

Light touch on a rigid surface with minimal force below a specific threshold reduces postural sway by providing additional sensory cues from the fingertips. The feasibility of maintaining light touch depends on subject characteristics and task difficulty. Therefore, we introduce a method of maintaining light touch by using electrical muscle stimulation (EMS). We applied it in a single-leg standing task involving healthy adult subjects. The subjects stood upright in a single-leg stance on a firm surface and on foam rubber (FR), respectively, under three conditions: no touch (NT, NT-FR), light touch without EMS (LT, LT-FR), and light touch in which EMS was applied based on the contact force (LT-EMS, LT-EMS-FR). The results showed that the force control by EMS helped maintain light touch and reduce postural sway compared with the no-touch condition. The amplitude of postural sway under the touch condition with EMS was equivalent to that under the touch condition without EMS.

Humidity sensor based on zeolite for application under environmental conditions

This paper describes a capacitive rotary position sensor that is characterized by its high compatibility with commercial resolvers. The main components are two electrode plates. Both parts are composed of simple circular or annular electrodes. The sensor is excited by two sinusoidal voltages, which are same as the excitation voltages of resolvers. These excitation voltages are applied to the stator transmitting electrodes. Then, these voltages arise on rotor electrodes by capacitive couplings. The stator pick-up electrodes detect voltages on the rotor that are amplitude-modulated due to the capacitance changes depending on the rotor position. The specifications of these signals are same as those of resolvers. Therefore, the rotor position can be calculated by the same way as resolvers. Due to the similarities with resolvers (excitation signals, generated signals and the way of calculate positions), this sensor can easily replace a commercial resolver. In this paper, the principle is verified by a prototype sensor, which shows a non-linearity error of +/-4 degrees.

Coupling error is one of the main error sources of the quartz tuning fork gyroscope. The mechanism of capacitance coupling error is analyzed in this article. Finite Element Method (FEM) is used to simulate the structure of the quartz tuning fork by ANSYS software. The voltage output induced by the capacitance coupling is simulated with the harmonic analysis and characteristics of electrical and mechanical parameters influenced by the capacitance coupling between drive electrodes and sense electrodes are discussed with the transient analysis.

PurposeThis paper aims to present an approach based on electrical impedance tomography spectroscopy (EITS) for the determination of water and ice fraction in low-power applications such as autarkic wireless sensors, which require a low computational complexity reconstruction approach and a low number of electrodes. This paper also investigates how the electrode design can affect the reconstruction results in tomography.Design/methodology/approachEITS is performed by using a non-iterative method called optimal first order approximation. In addition to that, a planar electrode geometry is used instead of the traditional circular electrode geometry. Such a structure allows the system to identify materials placed on the region above the sensor, which do not need to be confined in a pipe. For the optimization, the mean squared error (MSE) between the reference images and the obtained reconstructed images was calculated.FindingsThe authors demonstrate that even with a low number of four electrodes and a low complexity reconstruction algorithm, a reasonable reconstruction of water and ice fractions is possible. Furthermore, it is shown that an optimal distribution of the sensor electrodes can help to reduce the MSE without any costs in terms of computational complexity or power consumption.Originality/valueThis paper shows through simulations that the reconstruction of ice and water mixtures is possible and that the electrode design is a topic of great importance, as they can significantly affect the reconstruction results.

Low-depth modulation capacitive sensors, i.e. sensors where the capacitance variations caused by a measurand are only a small fraction of the total capacitance, are frequently encountered in measurement problems. Furthermore, also a conductance (e.g. due to parasitic conductive staining) between the sensor electrodes may affect the capacitance evaluation. We have implemented a capacitive sensor interface in a 0.25 μm CMOS process capable of measuring both conductive and capacitive coupling. The sensor interface provides an offset capacitance compensation and an offset conductance compensation such that a low-depth capacitance modulation can be mapped onto the full scale range of an Analog to Digital Converter. Experimental results for a prototype sensor interface with a capacitive slider array are presented.

This paper uses the co-planar interdigital electrode (IDE) sensor to measure water level. The researchers generally characterize the interdigital electrode sensor as a fringe field capacitor sensor developed on the printed circuit board and utilize the capacitor sensor's properties for liquid-level measurement. The interdigital electrode sensors illustrate more than one resonance at the higher frequencies, and in this study, the first resonance frequency fr -has been utilized for the water level measurement. Three water types are examined here: distilled, tap, and river. The study assesses that with the transition of water, the permittivity between the electrodes is changed and, it leads to a change in capacitance hence, the change in resonance frequency was observed. The proposed sensor can be represented by the lumped element equivalent series RLC circuit. The developed IDE sensor has good repeatability, small variability, and small hysteresis error. The maximum standard error for distilled, tap, and river water are 0.02833, 0.02503, and 0.02618, respectively, and the hysteresis error is less than 1.903% of full-scale output variation. The maximum error for the fr estimation is about ±2 Hz.

Sensing electrodes arranged in or around a display can provide input function for interactive displays. Commercially this is interesting because the sensing electrodes and electronics can be made in the same manufacturing process as that of the display itself thus reducing cost. In engineering terms, the electrodes measure capacitance changes resulting from the presence and movement of objects such as hands and fingers in front of the display. At the quasi-static frequencies used (100 kHz) the human body is conductive and the hands or fingers provide a screen between the capacitive electrodes. There is no need to touch the actual display and the overall system constitutes a touchless gesture input system. Determining the shape of the hand or fingers is a boundary condition reconstruction problem of finding the boundary of an earthed conductive object D from electrostatic measurements. This is the ill-posed problem of recovering the zero surface of a solution to Laplace's equation from Cauchy data on part of the boundary of a domain. The problem has similarities with object reconstruction in EIT or inverse scattering but is complicated because only a partial Dirichlet–Neumann map is available as experimental data. We suggest an algorithm where at each iteration we have an approximation ∂Dk to ∂D on which we calculate approximate Cauchy data by solving a Tikhonov regularized linear system. These data are used to modify ∂Dk by extrapolation towards the zero surface giving the next approximation ∂Dk+1. We implemented the algorithm in two and three space dimensions using the boundary element method for discretization. Numerical results using simulated data with added noise show that simply connected but not necessarily convex objects can be reconstructed with reasonable positional accuracy and approximate shape, but as might be expected the shape is more accurately determined near the plane of measurements.

This paper concerns the modeling of planar inductors with magnetic layers (one or two ferrite layers). A new equivalent circuit model (as simple as possible with a few parameters) is presented. The main new feature of this model is that the evolutions of both magnetic permeability (µ r ) and core losses (loss tangent, tanδ) versus frequency are taking into account. The model is suitable for low and high frequencies, it also takes into account skin and proximity effects, capacitive coupling between turns and capacitive coupling between the ground plane and the last turn.

Intrabody communication (IBC) is a promising modality that leverages the human body as a transmission medium for data communication, enabling low-power and compact solutions suitable for wearable and implantable biomedical devices. This work presents a comprehensive study of IBC channels, jointly evaluating galvanic coupling (GC) and capacitive coupling (CC) in both wearable and implantable configurations. Unlike prior works, which typically consider individual methods or limited configurations, this study combines three different analysis approaches. These are finite element method (FEM) simulations, equivalent circuit modeling, and experimental channel impulse response (CIR) characterization over a broad frequency range. This enables cross-method validation, and consequently the emergence of comparative insights. Full-wave electromagnetic simulations using FEM were performed up to 100 MHz using a multilayered cylindrical model with realistic anatomical and dielectric properties. CIR characterization was performed by transmitting baseband pseudorandom noise (PN) sequences through the modeled and experimental setups. Experimental validations up to 2.5 MHz were carried out using chicken tissue as a biological surrogate. Experimental communication channel gain results closely matched the simulation outcomes, confirming the accuracy of the proposed models and methodologies. Among all tested scenarios, the implantable CC configuration exhibited the highest channel frequency response (CFR) within the investigated frequency range.

Monitoring erosion progress of biodegradable drug carrying polymer coated on coronary drug eluting stents (DES) is largely hindered because of the small amount of coating material as well as the irregular profile of coating, both of which make the monitoring using traditional methods highly challenging. In our study, electrochemical impedance spectroscopy (EIS), a widely used method in the study of metal corrosion, was used to address the challenges traditional methods face. In vitro, remained mass and molecular weight drop data of film-like poly(lactide-co-glycolide) (PLGA) samples due to degradation were monitored using traditional mass loss measurement and size exclusion chromatography (SEC) methods. The obtained data were compared to the changes of capacitance and impedance measured by EIS from PLGA-coated stainless slices with an equivalent electrical circuit model. The results showed that the changes of the resistance and capacitance obtained by EIS, which indicates transformations of PLGA coating, can be correlated to the degradation measured by traditional methods, such as SEC. Furthermore, EIS method was applied to monitor and evaluate the erosion progress of a real stent with PLGA coating. Our results suggested that EIS method can accurately monitor real-time erosion process of thin polymer coatings on DES in situ.

Electropolishing of cylindrical workpiece of tool materials using disc-form electrodes