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Random instrument noise (a, b) exhibits a Gaussian distribution. A noise source interferes with the electrical field lines of the IDS causing erratic noise patterns over a wide range of values (c, d). The investigated shield reduces this noise and restores the instrument noise pattern (e, f).
Source publication
Interdigitated dielectrometry sensors (IDS) are capacitive sensors investigated to precisely measure the relative permittivity (𝜀r) of insulating liquids. Such liquids used in the power industry exhibit a change in 𝜀r as they degrade. The IDS ability to measure 𝜀r in-situ can potentially reduce maintenance, increase grid stability and improve safet...
Citations
... The work of Alex Risos [23], [24], [25], [26] on interdigitated capacitive sensors employs the differential principle in which the reference sensor is thermally coupled with the transformer oil sensing probe. He also uses a four wire bridge measurement technique which significantly suppresses the effect of lead wire impedance. ...
This paper describes the development of an array of coplanar capacitive sensors applied to marine icing. Current atmospheric icing monitoring systems consider single phase conditions in their operation. Marine icing conditions present a unique environment where the liquid water phase effects cannot be neglected and require a novel approach. We have conducted an initial proof of concept and propose a new icing monitoring system which can distinguish between the individual phases. A numerical model confirmed our initial hypothesis of the system’s ability to discriminate the multiphase domains based on the array of geometrically dissimilar capacitive sensors. In addition, we also developed a novel experimental technique based on a comparative study under constant conditions to eliminate the need for an independent ice accretion monitoring system normally required in sensor development. The new approach promises a better characteristic in marine icing monitoring systems or in similar applications where multiphase dielectric is present.
... 28,29 Since the object of evaluation of this research was the portion of the mini-implant that remains inserted in the bone tissues of the patient, the solution for the experiment should mimic the electrolytic aggression caused by the environment and, so, Ringer's lactate solution was chosen as it is isotonic to blood plasma. 30,31 Artificial saliva was described as an environment in polarisation tests. 5,22,24,25 However, choosing this solution would only make sense if the study assessed the corrosion resistance of the head and neck of the mini-implant, 24 as then it would simulate its clinical application. ...
... Como o ensaio de polarização mede a corrente de elétrons do eletrodo de trabalho (anodização), correntes elétricas oriundas de ondas eletromagnéticas externas podem modificar as condições eletromagnéticas da célula eletroquímica, influenciando a corrente de elétrons no interior desta célula e, consequentemente, comprometendo todo o ensaio de polarização 20 . Para evitar tais alterações, todos os ensaios de polarização desta pesquisa foram realizados no interior de uma Gaiola de Faraday ligada ao aterramento do sistema elétrico. ...
Introdução
Mini-implantes ortodônticos são dispositivos de ancoragem confeccionados à base de titânio, possuindo uma camada de óxido de titânio, que desempenha função importante na resistência à corrosão.
Objetivo
O objetivo deste estudo foi avaliar a resistência à corrosão e a microestrutura superficial de mini-implantes novos, utilizados que foram perdidos precocemente e os que obtiveram sucesso de estabilidade, analisando se o processo de corrosão influencia a falha ou a perda de estabilidade, a fim de se comparar com as principais causas de sucesso e insucesso clínico.
Material e método
A amostra foi composta por 3 grupos de 7 mini-implantes divididos da seguinte maneira: Grupo C: mini-implantes na sua forma original, como são recebidos do fabricante (controle); Grupo PE: mini-implantes utilizados em pacientes e que apresentaram perda de estabilidade precoce em até 2 meses (média de 33,5 dias); Grupo E: mini-implantes utilizados em pacientes com sucesso de estabilidade (média de 230 dias). A análise visual da superfície da rosca dos mini-implantes foi feita através de microscópio eletrônico de varredura e todos foram submetidos a ensaio de polarização cíclica potenciodinâmica em potenciostato.
Resultado
A microestrutura superficial não foi significativamente alterada pela permanência e perda precoce de estabilidade em seus sítios ósseos.
Conclusão
Os dados sugeriram que a corrosão não foi fator associado à falha do dispositivo ou perda de sua estabilidade, sendo outros fatores, como o tipo do mini-implante, o seu comprimento e o local de implantação, considerados mais preponderantes com influência no seu insucesso.
... [1][2][3] Such materials are synthesized through a simple and efficient self-assembly method by ordered aggregation into high-dimensional architectures. 4 Moreover, 3D nanoarchitectures have potential applications in photoelectric devices, 5 catalysts, 6 lithium-ion batteries, 7 and sensors. [8][9][10] 3D nanostructures with controllable properties can be prepared through several methods, such as low-temperature aqueous solution route, 11,12 precipitation process, 13 and hydrothermal technology. [14][15][16] The powder obtained by hydrothermal method has advantages in terms of uniform particle size, high purity, and good crystallization. ...
Three-dimensional (3D) metal inorganics have gained tremendous interests for a series of applications. Here, we prepared TiO2 microspheres, urchin-like TiO2, and flower-like TiO2 by hydrothermal method. The morphologies of the three 3D TiO2 nanostructures were characterized by scanning electron microscopy and X-ray diffraction analyses. The electrochemical behaviors of the 3D TiO2 nanostructures were investigated by electrochemical impedance spectroscopy and cyclic voltammetry studies. Results showed that 3D TiO2-modified electrodes exhibited improved electrochemical performance compared with bare electrode. The three 3D nanostructures were then used with a modified glassy carbon electrode to detect dopamine (DA). According to the experimental results, the flower-like TiO2/GCE demonstrated excellent electrochemical performance than the two other electrodes. The enhanced electrochemical performance of the 3D flower-like TiO2/GCE is mainly affected by the structure of anatase crystal, which is the most important factor for the enhanced electrochemical performances toward DA detection. The flower-like TiO2/GCE, urchin-like TiO2/GCE, and TiO2 microspheres/GCE possessed linear ranges of 0.02–160, 1–180, and 1–160 μM, with limit of detection values of 0.007, 0.31, and 0.33 μM, respectively.
... As the parasitic capacitance is not a constant offset anymore, the C air value is not constant and the calibration with C air ∼ ε r = 1 becomes invalid [27]. Additionally, temperature affects the insulator's dielectric properties [28]- [30] and therefore the accuracy had suffered in many studies [8], [10], [25], [31]. An example of this problem was also studied in [32]. ...
... One way to theoretically achieve this is by closing the gap, g, between the electrodes to a minimum as shown in [31]. This may bring in other problems such as manufacturing limitations or short-circuiting of the electrodes due to tolerances. ...
... The IDS capacitance can be calculated based on the surface charges σ (V 0 ) [27], [31] for N electrodes of V 0 , ...
Interdigitated dielectrometry sensors (IDS) are used as capacitive sensors to measure the permittivity, εr, and DC conductivity, σDC, (e.g. dissipation factor tanδ) of oils. Both variables can yield the oil’s health. However, parasitic capacitances can be a source for a temperature dependence, impreciseness and inaccuracy. This study shows a design of an IDS that uses deflector electrodes to reduce parasitic capacitance effectively. The design parameter for a next generation IDS that is highly accurate, precise and effectively insensitive to temperature was determined using finite element modelling. The air capacitance between 30 and 90 °C was stable at Cair = 6.27 ± 0.02 pF. Measurements of standard transformer oil have shown an accuracy of 99% for εr and σDC. The conductivity detection threshold was as low as 6 pS/m ≈ tanδ = 0.001. Additionally, Cair correlated to 93% with the air humidity. This IDS design can be applied in various applications where accurate permittivity and conductivity monitoring of liquids in environments with temperature fluctuations is required.
... Dielectrics such as PTFE can cause a parasitic capacitance, thus altering the measurement as the electric flux is proportional to ε r . 31,32 In order to reduce the interference with the ε r measurement, the height of the PTFE lip, that is, the thickness of the PTFE that extends in the y-direction between the electrodes, should be minimized. However, this lip height must be sufficiently large to hold the electrodes rigidly in position [ Fig. 2(c)]. ...
... Parasitic effects such as stray capacitances or external electric fields can also interfere with the measurement. 31,33,34 This problem is addressed through an electric shield, a 3D Faraday housing, that is connected to the ground of the measurement instrument. A sample exchange arrangement provides the option to measure the air capacitance and the MUT capacitance without interfering with the mechanical arrangement of the setup. ...
A measurement of the complex permittivity, εr, of a liquid can give valuable information about the molecular polarizability and dielectric losses. This can be obtained by means of an impedance measurement using a parallel plate test cell. However, highly accurate and precise measurements are challenging, in particular when measuring as a function of temperature. Thermal expansion affects the geometry of a test cell and thus the measured capacitance from which εr is calculated. In this paper, a broadband four-terminal dielectric test cell is presented that is insensitive to temperature fluctuations. This was achieved by means of a cell geometry exploiting the thermal expansion coefficient of different materials. Experimental measurements on the manufactured cell yielded a stable capacitance of 35.322 ± 0.001 pF across 20 °C–90 °C. The capacitance stayed within ±0.01 pF over multiple experimental cycles of cleaning and assembly. A finite element modeling showed a theoretical accuracy in measuring εr better than 99.995%. The measured εr values for a number of standard liquids showed an agreement of 99.7% compared to literature values.
... The electrostatic potential between the electrodes was V = 1 in the simulations in section II, E is the electric field and ε 0 is the permittivity of free space. Indications for such parasitic capacitances of IDS were observed in previous work [20] and [29]. The expected increase of ε r during the oil's lifetime is generally about +5% to +10% [7]- [10], [30], which can easily be swamped by the parasitic capacitance in the system. ...
... Shenzhen JDB Technology Co., Ltd, Shenzhen, China), therefore the permittivity value for the soldermask was approximated to 4.5 as ε r = 4 to 5 is a common value for epoxies in literature [35]. Using this value has shown to give accurate results with experimental observations in preceding research [29]. While the relative permittivity of the soldermask ε r,SM and insulator ε r,ins was held constant at 4.5, the permittivity of the oil, ε r , was varied from 2 to 5, covering a wide range of oil permittivities. ...
An accurate measurement of the relative permittivity, εr, of industrial oils using interdigitated dielectrometry sensors (IDS) is challenging due to the parasitic capacitance caused by the IDS spatial structure. In this paper, the investigated IDS structure consists of a substrate, a ground plane, an insulating layer below the electrodes and a soldermask above the electrodes having a periodicity of λ. This structure was simulated to determine the influence on the expected values of capacitance C, sensitivity S and deviation D (accuracy) for typical values of εr for industrial oils. It is shown that for particular structure ratios and values of εr, the parasitic capacitance can be compensated in order to provide an accurate measurement of εr. A standard rapid and cost efficient printed circuit board (PCB) technology is used to manufacture an IDS based on the simulations to verify the expected high accuracy in practice. Experiments conducted with this IDS structure on both new and degraded oils showed a high accuracy ≈ 99.5 %, verifying the simulations. These results have the potential to reduce the number of IDS design iterations in order to carry out highly accurate and precise measurements. This may go beyond the in-situ monitoring of oil degradation such as a number of related sensing applications employing interdigitated sensor platforms.
... Capacitive measurements are generally carried out to measure the permittivity/dissipation factor of oil samples as a way of evaluating the oil condition. Therefore, RRI have decided to explore the use of IDS (interdigitated sensors) for in-situ measurements of permittivity [4]. ...
Lifetime diagnostics of distribution transformers have traditionally not been done due to the lack of financial benefit. Although online monitoring is used for power transformers, the cost of the systems used make it infeasible for distribution transformers. However, with NZ’s aging distribution network and introduction of new technologies such as photovoltaic systems and electric vehicle charging, which impose a highly fluctuating load profile, the capacity to have online monitoring of distribution transformers is becoming an increasingly attractive option.
Robinson Research Institute (RRI) and ETEL transformers have been collaborating to develop cost-effective transformer diagnostic systems. The current focus of the team at RRI is on three aspects of transformer diagnostic sensing: thermal modelling and load response of the transformer; DGA sensors; and oil quality sensors. Therefore RRI has constructed a small experimental transformer test-facility to support the R&D program with in-situ testing of sensors and characterisation of the behaviour of distribution transformer parameters under different scenarios.
Fibre-optic based sensors are one of the type of sensors being explored, which are ideal for use within high voltage windings of transformers due to their non-conductive characteristic. The winding temperature is of interest as it affects the life of a transformer. Fibre optic temperature sensors have been installed and tested within a custom-made single-phase 30kVA transformer in our test facility. Temperature measurements were carried out at several points within the transformer windings, including at the estimated hot spot within the windings. A number of heat run tests (based on the IEC 60076 standard) with different loading conditions up to 135% of the rated power were performed by applying short circuit impedance loading. Different ambient temperature and ventilation conditions were investigated.
We will give a general overview of our diagnostic sensor development program and discuss in more detail the use of Fibre Bragg Gratings (FBG) for the measurement of winding temperature rise, in particular the advantages and disadvantages of using this temperature measuring technique within distribution transformers. We will also discuss the measured dynamic thermal behaviour of transformers in comparison to industry standards.
... Therefore, the value of μ can be an indicator of the molecular polarity and potentially an effective measure of monitoring paraffinic oxidation. The measurement of μ can be performed by capacitive probes such as interdigitated dielectrometry sensors [15][16][17][18][19] which are readily available and have been used to measure hydrocarbon liquids. Such probes can be made of highly cost efficient and robust materials (e.g. ...
... Such probes can be made of highly cost efficient and robust materials (e.g. printed circuit boards [15] and polytetrafluoroethylene [19]) potentially preserving their functionality over long time scales. The result of a capacitive measurement can be expressed in the relative permittivity r that is linked to μ via Clausius-Mossotti related equations [13,14,[20][21][22][23]. ...
A study of the link between the infra-red (IR) absorbance and the relative static permittivity 𝜀r of liquid hydrocarbons is of special interest for developing in-situ oxidation monitoring tools. In particular, where IR measurements are difficult to implement but cost efficient and durable capacitive probes can be used. This paper will explore this link by exposing a paraffinic hydrocarbon to oxidation in an accelerated degradation process, while measuring the IR absorption and 𝜀r values during this process. It is shown to what extent the IR response of the hydrocarbon liquid changes in the 500 to 4000 cm-1 window, and how this can be translated into a measured increase in 𝜀r during oxidation time. The correlation coefficient between IR absorbance at around 1720 cm-1 and 𝜀r increase with oxidation time was 99.7%. This remarkably good agreement shows that capacitive probes have the potential to be used as a substitutional in-field tool for in-situ degradation monitoring of hydrocarbon liquids.
This paper proposes an online monitoring method of metal-oxide arrester (MOA) based on passive RFID sensor tag and mind evolutionary computation (MEC). Firstly, an RFID sensor tag is designed to collect the leakage current of MOA, so as to realize the rapid fault location and equipment life cycle management. The proposed RFID sensor incorporates the sensor data into its ID information. The proposed power management block adopts a new architecture of a low-voltage DC-DC charge pump after a single-stage rectifier circuit. A method of MOA condition monitoring based on MEC is proposed. According to the measured operating voltage and leakage current, the parameters k and α which can reflect the aging condition of MOA are solved by using MEC's better optimization calculation ability, so as to monitor the MOA condition. In addition, the influence of harmonic voltage on the algorithm is analyzed through MATLAB simulation. The results show that the designed sensor tag can effectively measure the leakage current, and the proposed monitoring algorithm can accurately calculate the relevant parameters reflecting the state of MOA. Moreover, under the influence of harmonic voltage, the maximum errors of parameters k and α are 1.8% and 2.0%. Compared with the existing monitoring technology, it has the advantages of low cost, high precision and rapid fault location, which provides a new method and idea for on-line monitoring of MOA.
