Optimization of the coplanar interdigital capacitive sensor

Huang, Yunzhi; Zheng, Zhan; Bowler, Nicola

doi:10.1063/1.4974695

Cited by 36 publications

(30 citation statements)

References 9 publications

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“…A greater penetration depth will lead to a longer detection range. The depth that the electric field penetrates to the space is roughly proportional to the spatial wavelength λ, which is defined as the distance between two consecutive electrodes of the same polarity [17]. This electrode configuration provides two different spatial wavelengths, and the capacitive response is correlated with the distance.…”

Section: Methodsmentioning

confidence: 99%

Improved Capacitive Proximity Detection for Conductive Objects through Target Profile Estimation

et al. 2019

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The accuracy of a capacitive proximity sensor is affected by various factors, including the geometry and composition of the nearby object. The quantitative regression models that are used to seek out the relationship between the measured capacitances and distances to objects are highly dependent on the geometrical properties of the objects. Consequently, the application of capacitive proximity sensors has been mainly limited to detection of objects rather than estimation of distances to them. This paper presents a capacitive proximity sensing system for the detection of metallic objects with improved accuracy based on target profile estimation. The presented approach alleviates large errors in distance estimation by implementing a classifier to recognize the surface profiles before using a suitable regression model to estimate the distance. The sensing system features an electrode matrix that is configured to sweep a series of inner-connection patterns and produce features for profile classification. The performance of the sensing modalities is experimentally assessed with an industrial robot. Two-term exponential regression models provide a high degree of fittings for an object whose shape is known. Recognizing the shape of the object improved the regression models and reduced the close-distance measurement error by a factor of five compared to methods that did not take the geometry into account. The breakthroughs made through this work will make capacitive sensing a viable low-cost alternative to existing technologies for proximity detection in robotics and other fields.

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Section: Methodsmentioning

confidence: 99%

Improved Capacitive Proximity Detection for Conductive Objects through Target Profile Estimation

et al. 2019

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“…More recently, a finite-element modeling (FEM) approach has been employed to investigate the question of how to optimize the design of the interdigital sensor for various purposes (Huang et al 2017;Shao and Bowler 2017). Subject to certain constraints, such as available dimensions of the sensor for a certain type of cable application, the need to achieve a value of C that is above the instrument noise floor, and the limitations of sensor fabrication approaches, the sensor sensitivity to expected changes in the material permittivity as a function of its aging has been modeled and used as a metric by which to seek an optimal sensor design.…”

Section: Electrode Designmentioning

confidence: 99%

“…The adjustable parameters in the design process are taken to be the number of electrode digits, the width of those digits, and the separation between them-although these are not completely independent of one another. In the planar geometry treated by Huang et al (2017), it was shown that there is a design trade-off between the sensor's sensitivity and the penetration depth of the fringing field into the test piece. In other words, the sensor sensitivity to permittivity changes is better for electrodes whose digits are close together, but the penetration depth of the electric field is smaller in this case.…”

Section: Electrode Designmentioning

confidence: 99%

“…Both tools include electrostatic field solvers for 2D and 3D geometries. Huang et al (2017) investigated the effect of varying the geometrical parameters g, w (and consequently the number of digits, N) of a coplanar, interdigitated sensor with fixed overall dimensions upon its output capacitance and sensitivity. A schematic diagram of the sensor is given in Figure 6-1 (Huang et al 2017).…”

Section: Fem Simulationsmentioning

confidence: 99%

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Interdigital Capacitance Local Non-Destructive Examination of Nuclear Power Plant Cable for Aging Management Programs

Glass

Fifield

Bowler

et al. 2018

Self Cite

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This Pacific Northwest National Laboratory milestone report describes progress to date on the investigation of non-destructive test methods focusing on local cable insulation and jacket testing using an interdigital capacitance (IDC) approach. Earlier studies have assessed a number of non-destructive examination (NDE) methods for bulk, distributed, and local cable tests. A typical test strategy is to perform bulk assessments of the cable response using dielectric spectroscopy, Tan , or partial discharge followed by distributed tests like time domain reflectometry or frequency domain reflectometry to identify the most likely defect location followed by a local test that can include visual inspection, indenter modulus tests, or Fourier Transform Infrared Spectroscopy (FTIR) or Near Infrared Spectroscopy FTIR (FTNIR). If a cable is covered with an overlaying jacket, the jacket's condition is likely to be more severely degraded than the underlying insulation. None of the above local test approaches can be used to evaluate insulation beneath a cable jacket. Since the jacket's function is neither structural nor electrical, a degraded jacket may not have any significance regarding the cable's performance or suitability for service. IDC measurements offer a promising alternative or complement to these local test approaches including the possibility to test insulation beneath an overlaying jacket.

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“…The principle of the CI technique is based on the fringing effect of electric field. Compared to some of the traditional NDE techniques, the CI technique has some unique features, such as it is a non-contact technique, it only requires single side access to the specimen, and can work on a wide range of material types [21][22][23][24]. Therefore, the CI technique is widely used in the non-destructive testing field, such as humidity monitoring, ageing degree testing and compact damaging detection [25][26][27][28][29][30].…”

Section: Introductionmentioning

confidence: 99%

Capacitive Imaging Technique for the Inspection of Composite Sucker Rod

Wang

Yin

et al. 2019

Chin. J. Mech. Eng.

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Composite sucker rod has been extensively used due to its high strength, light weight and corrosion resistive nature. However, such composite sucker rod is difficult for conventional non-destructive evaluation (NDE) techniques to inspect because of its complex material and/or structure. It is thus useful to embark research on developing novel NDE technique to comply the inspection requirement. This work demonstrates the feasibility of using the capacitive imaging (CI) technique for the inspection of composite sucker rod. Finite element (FE) models were constructed in COMSOL to simulate the detection of defects in the glass-fiber layer and on the carbon core surface. An FE Model based inversion method is proposed to obtain the profile of the carbon core. Preliminary CI experimental results are then presented, including the detection of surface wearing defect in the glass-fiber layer, and obtaining the profile of the carbon core. A set of accelerated aging experiments were also carried out and the results indicate that the CI technique is potentially useful in evaluating the ageing status of such composite sucker rod. The CI technique described in this work shows great potential to target some challenging tasks faced in the non-destructive evaluation of composite sucker rod, including quality control, defect detection and ageing assessment.

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Optimization of the coplanar interdigital capacitive sensor

Cited by 36 publications

References 9 publications

Improved Capacitive Proximity Detection for Conductive Objects through Target Profile Estimation

Improved Capacitive Proximity Detection for Conductive Objects through Target Profile Estimation

Interdigital Capacitance Local Non-Destructive Examination of Nuclear Power Plant Cable for Aging Management Programs

Capacitive Imaging Technique for the Inspection of Composite Sucker Rod

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