Non-contact Electrostatic Voltmeter Research Articles

Voltage mapping and local defects identification in solar cells using non-contact method

Electroluminescence, infrared imaging, and current–voltage curve techniques are used to detect and map underperforming cells in a photovoltaic module or the modules in a photovoltaic string. In this work, we present a non-contact electrostatic voltmeter technique to detect and map the underperforming spots in a cell and the cells in a module. This non-contact technique directly maps the charged surface voltage (671 mV) of the superstrate glass, and it had an 11-mV difference with the voltmeter values (660 mV). Another data set of voltage values obtained by electroluminescence images conversion into a voltage map showed a difference of 7 mV with the non-contact voltmeter values. The direct voltage values obtained at various good and poor-performing spots of the cells using this technique are 3.69 V and 3.79 V and are validated using the voltage values obtained in electroluminescence analysis and the difference in voltage obtained by the two techniques is determined to be less than 2%. In this work, we combine the strengths of two complementary techniques of the electrostatic voltmeter (strength: quantitative) and electroluminescence (strength: spatial mapping) to obtain a quantitative spatial mapping of defects. Furthermore, this work is extendable to detect the poor-performing modules in solar PV power plants.

High-accuracy characterization of pyroelectric materials: A noncontact method based on surface potential measurements

The characterization of pyroelectric materials is essential for the design of pyroelectric-based devices. Pyroelectric current measurement is the commonly employed method, but can be complex and requires surface electrodes. Here, we present noncontact electrostatic voltmeter measurements as a simple but highly accurate alternative, by assessing thermally-induced pyroelectric surface potential variations. We introduce a refined model that relates the surface potential variations to both the pyroelectric coefficient and the characteristic figure of merit (FOM) and test the model with square-shaped samples made from PVDF, LiNbO3 and LiTaO3. The characteristic pyroelectric coefficient for PVDF, LiNbO3 and LiTaO3 was found to be 33.4, 59.9 and 208.4 [Formula: see text]C m[Formula: see text]K[Formula: see text], respectively. These values are in perfect agreement with literature values, and they differ by less than 2.5% from values that we have obtained with standard pyroelectric current measurements for comparison.

Application of non-contact electrostatic voltmeter to identify underperforming modules in grid-connected photovoltaic systems

This paper presents a technique that uses maximum power point voltage (Vmpp) to quantitatively identify the underperformance photovoltaic (PV) modules in grid-connected PV systems using a non-contact Electrostatic Voltmeter (ESV). Unlike the other existing techniques, this technique doesn't require the module's disconnection from the grid or other modules in a string. First, in this work, the ESV was tested for the application of thin film modules (off-grid and on-grid), and a comparison of the ESV sensed voltages with the voltmeter voltage values indicated a difference of less than 2%. Second, the least power-producing module was identified by the IV curves analysis and the Vmpp technique, and the results were compared. The comparison of both characterization tools quantitatively pointed out to the same module as the lowest performance module. It is a contactless, time and cost-saving method and is useful for quantitatively determining defective and poor-performing PV modules in large power plants where continuity of the energy production is preferred during the testing.

Experimental characterization of electric potential uniformity at the surface of polymer plates corona charged by multiple-row needle-type electrodes

Diverse configurations of needle-type electrodes are commonly used to generate DC or AC corona discharges in various industrial applications. Previous studies confirm that the amount of charges generated by corona discharge is controlled by several factors such as the level of applied voltage, the ambient conditions, as well as the geometry of the electrode system. This paper aimed to evaluate the distribution uniformity of the charges generated by multiple-row needle-type electrodes and deposited on the Polyvinyl Chloride (PVC) plate surface, either at rest (“static” regime) or in motion (“dynamic” regime) under the corona electrode. The potential at the PVC plate surface was measured by a non-contact electrostatic voltmeter. The electric potential maps resulting from the experiments carried out in “static” regime, point out that the uniformity of the corona charging effect generated by the electrodes is related to their geometry and the level of the applied voltage. In the “dynamic” regime experiments, the surface potential profiles show that the distribution of electric potential on corona-charged polymer plates depends on the number of needles and the direction of movement under corona electrode system. Comparing the results obtained in this paper with the results obtained in previous studies, lead us to a general conclusion that the uniformity can be improved, to attain values higher than 95%, and this depends on the geometry of the electrode system and on the direction of the movement of the polymer plates in the electric field.

Study of the Influence of the Different Parameters of the Atmospheric DBD Treatment on the Surface Roughness and the Electric Potential Distribution Generated After the Tribocharging of Polypropylene

Square plates of polypropylene (PP), dimensions 100 mm × 100 mm × 4.5 mm, were treated by atmospheric dielectric barrier discharge (DBD) generated between two disk-type electrodes (Ø 75 mm), energized from an ac amplifier 30 kV, 20 mA. The study aimed at evaluating the factors that affect the roughness and the triboelectric behavior of the plasma-treated samples. The alteration of surface aspect after each treatment was clearly visible with the naked eye and the changes were confirmed by measurements carried out with a portable roughness meter (Surftest SJ-210) and a digital microscope (Keyence VHX-7000). The roughness of the PP samples increased from an initial arithmetic mean Ra = 0.06 μm (±0.01 μm) and standard deviation Rq = 0.08 μm (±0.01 μm) to Ra = 0.22 μm (±0.03 μm) and Rq = 0.25 μm (±0.03 μm), respectively. These increases were highly dependent on the air gap distance (10.5-13.5 mm), the treatment time (5-20 min), and the configuration of the DBD cell, i.e., the number (one or two) and the thickness (4-5 mm) of the glass dielectric barriers. Untreated and DBD-treated samples were tribocharged in a linear tribometer, to evaluate the effect of the cold plasma treatment on the electric potential generated on the polymer surface by the triboelectric effect. The electric potential measured by a noncontact electrostatic voltmeter (Trek, 341B) was higher and better distributed over the surface of the plasma-treated samples.

DC and AC electric field analysis and experimental verification of a silicone rubber insulator

This paper presents the electric field analysis as well as the experimental verifications of a silicone rubber insulator by considering DC and AC voltage conditions. As a first step, a 3D electric field simulation of the insulator was performed by using a commercially available software based on finite element method. DC voltage and 50 Hz power–frequency voltage simulations were conducted for the given insulator. Low frequency field distribution along the insulator has been investigated to find threshold frequency values for resistive and capacitive field regions. The effect of the conductivity of air surrounding the insulating system on the electric field was evaluated. For each condition, electric potential and field distribution along the creepage path of the insulator was obtained. In addition to the simulation studies, voltage measurements under AC and DC conditions utilizing a different approach for the silicone rubber insulators were conducted on the insulator by using a non-contact type electrostatic voltmeter to validate the simulation results.

Experimental study of controlled active neutralization of polypropylene films

AC corona discharge is widely employed for neutralizing the electric charges at the surface of insulating bodies: films, plates, granules, etc. If uncontrolled, this active neutralization process is accompanied by the persistence of a residual charge at the surface of the treated bodies. The aim of this present work is to demonstrate experimentally the efficiency of the controlled active neutralization using AC corona generated in a triode-type electrode configuration, with the grid connected to the ground. The experimental study was carried out on DC corona charged polypropylene films that were neutralized by a sinusoidal corona discharge at industrial frequency (50 Hz). The distribution of the electric potential at the surface of the charged and neutralized samples were measured by a non-contact electrostatic voltmeter. The factors under study were: the amplitude of the AC voltage applied to the corona electrode of the triode system, the duration of exposure to the corona discharge, the scanning speed, and the spacing between the grid and sample. The experimental results obtained show that the neutralization rate is close to 100%, i.e. the electric potential profiles obtained at the surface exposed to AC corona discharge show the absence of the residual charge. The results show that the efficiency of the controlled active neutralization depends on the energy that the AC corona discharge imparts to the charged samples, and that affects the trapped bulk charge.

Surface potential stability of large-area Teflon PTFE electret dosimeters of different thicknesses

The effects of charge polarity and thickness on the surface charge potential stability responses of large-area Teflon polytetrafluoroethylene (PTFE) discs electrostatically charged by a new “modified single point-to-plane corona poling rotating system” were studied. Large-area Teflon discs (6 cm diameter) with 0.2, 0.5 and 1 mm thicknesses were used to produce both negatively or positively charged Teflon discs, at the same charging conditions. The deposited charge potential stability of the Teflon discs of different thicknesses monitored by a non-contacting electrostatic voltmeter for an extended time were monitored up to 77 days. Some inter-related parameters such as surface charge potential and external electrostatic field, internal electrostatic field, surface charge density, and the storage duration were also studied. The thick large-area Teflon disc electrets produced provided a steady-state charge stability on either negative (0.2, 0.5 and 1 mm thick) or positive (1 mm thick) surface charge potentials for the long period studied. The Teflon electret discs produced demonstrated having the highest charge potential stability in thicker electrets (1 mm), either negative or positive polarity, with provision of high potential for different applications in general and radiation protection dosimetry in particular.

Laboratory measurements of dusty surface charging in plasma.

A novel method is developed to study the charging of a conducting surface covered by a thin dust layer in plasma. The potential profile in the dust layer and the floating potential of the surface underneath are measured directly by embedding conducting wires in the dust and connecting the wires to a measurement plate outside the vacuum chamber, where a Trek non-contacting electrostatic voltmeter measures the floating potential of the measurement plate. Laboratory experiments are carried out to study plasma charging of a conducting plate covered by lunar dust simulant, JSC-1A. The results show that the plate potential is dependent on both the ambient plasma condition and the dust layer thickness. The current balance condition controls the floating potential of the dust surface while the dust layer acts as a capacitor and controls the potential of the plate with respect to the dust surface. Hence, a dust covered conducting plate will be charged more negatively than a clean plate.

Measurement of surface potential of non-uniformly charged insulating materials using a non-contact electrostatic voltmeter

Non-contact measurements performed with the auto-compensated electrostatic induction probe of an electrostatic voltmeter are often employed to characterize the charging state of insulating materials, such as films or non-woven media. The aim of the paper is double: (i) describe a simple method for assessing the resolution of such a probe; (ii) discuss the significance that can be attributed to the value displayed by the electrostatic voltmeter when the charge is non-uniformly distributed at the surface of the bodies examined by the probe and no constant surface potential can be defined. The measurements were performed for some simple experimental models that simulate surface potential non-uniformity of constant-charge insulating bodies. By examining the different surface potential distribution curves that were obtained for each of the situations under study, it is possible to estimate the resolution of the probe. A commercial computer program based on the superficial charge simulation method was employed for the numerical analysis of the electric field in a simplified 2-D representation of the geometric system formed by the probe, the experimental model, and the grounded plate. The potential that anneals the electric field at the surface of the probe (to simulate its principle of operation) was calculated by an iterative method. A good agreement was found between the results of the numerical simulations and the experimental data. The errors that can be made in the interpretation of the results of surface potential measurements are illustrated by the case of a non-uniformly-charged non-woven polypropylene fabric.

Dependence of contact electrification on the magnitude of strain in polymeric materials

We present a new experimental approach to systematically study the effect of material strain on contact electrification. Thin sheets of latex rubber are variably strained by stretching over a hollow cylinder, analogous to a drum. The strained sheets are repeatedly contacted with another surface by a computer-controlled apparatus. The surface potential on the latex rubber is measured in real time by a non-contact electrostatic voltmeter. For unstrained latex rubber, we find that contact with polytetrafluoroethylene (PTFE) leads to a negative surface potential that progressively increases in magnitude to more negative values with increasing number of contacts. When the latex rubber is strained, contact with PTFE causes the surface potential of the latex rubber to shift to less negative values. At strains of more than ∼50%, the polarity of the surface potential is reversed, such that contact with PTFE causes the latex rubber to charge positively. These results indicate that contact electrification intimately depends on the degree of material strain, and may explain how spatial inhomogeneities of charge exist on contacted surfaces and why there is a lack of reproducibility in contact charging experiments.

Active ingredient-containing chitosan/polycaprolactone nonwoven mats: Characterizations and their functional assays

This study demonstrates a facile method developed to generate a chitosan/polycaprolactone (CS/PCL) nonwoven mat. All nonwoven mats are composed of microfibers with an average diameter of 2.51±0.69μm. The X-ray photoelectron spectroscopy data indicate that positively charged nitrogen was generated on the surface of the mats after undergoing CS coating. By using a non-contacting electrostatic voltmeter, we determined that the nonwoven mats exhibited a positive potential and the charge density of the CS/PCL nonwoven mat was in proportion to the thickness of the CS overlayer. Moreover, platelet aggregation and anti-bacterial ability were enhanced by the CS/PCL nonwoven mat as compared to that of PCL nonwoven mat alone. The enhancements of the CS/PCL nonwoven mat on platelet aggregation are further promoted by incorporating a 1mM calcium ion in its CS overlayer. We also find that the addition of tea tree oil in the CS overlayer significantly inhibited LPS-induced nitrite formation in Raw 264.7 macrophages. In conclusion, our CS/PCL nonwoven mat possesses pharmacological effects including an increase of platelet aggregation, anti-bacterial, anti-adhesive, and anti-inflammatory activities. The performance of this CS/PCL nonwoven mat can be further promoted by incorporating active compounds to exert therapeutic effects in wound healing.

A modified potential probe for induction charging risk assessment

Practical assessment of risks for Electrostatic Discharge (ESD) failures of semiconductor devices, due to charges induced on devices in a manufacturing or repair environment of electronics has been difficult, because easily measurable parameters such as the electrostatic field and the potential of a charged surface do not directly quantify the risk. In this paper a new method of assessing the risks with induction charging of a sensitive device is presented by introducing a well-defined dummy device, which is a simple modification of the probe of DC type non-contacting electrostatic voltmeter. By placing the modified potential probe (mimicking large sensitive device) in front of charged surface, risks of ESD failure for a device due to induction charging can be assessed. The electrostatic response of the probe at different distances between charged surface and the probe has been verified by numerical model calculations.

Surface strain sensing with polymer piezoelectric film

A sensing technique for surface strain distributions of a structural component using piezoelectric polymer films is demonstrated. A piezoelectric polymer (polyvinylidene fluoride, PVDF) film is mounted onto the structure surface, and the electric potential induced by the surface deformation is measured with the aid of a non-contact electrostatic voltmeter. The measured potentials are converted into surface strain components using a theoretical formula derived on the basis of linear piezoelectricity. The validity and accuracy of the procedure are illustrated for (i) a plate with a penetrating circular hole and (ii) a plate with a non-penetrating slit-like groove on the back-surface, under in-plane compressive loading. Also, an alternative method for visualization of surface strain patterns using electrically charged powders is demonstrated for plates with back-surface defects.

Mechanism of Electrochemical Detection of DNA Hybridization by Bilayer Lipid Membranes

Recent reports have suggested that bilayer lipid membranes (BLMs) and stabilized self-assembled bilayer lipid membranes (s-BLMs) can detect DNA hybridization, but have not explained the actual mechanism of signal generation. The electrochemical experiments have demonstrated that hybridization of complementary single-stranded DNA (ssDNA) 20mers, where one sequence is terminated by a C16 alkyl chain to assist incorporation into the lipid membrane, can cause reduction of ion current through membranes. The present work has explored egg-phosphatidylcholine monolayers at the air–water interface as a model of BLMs, and has investigated the effect of DNA on pressure–area relationships, electrostatic fields as measured using a noncontacting electrostatic voltmeter, and fluorescence microscopy of membranes that were loaded with fluorescein labelled DNA. Each of these experiments confirms that ssDNA partitions onto and changes the structural and electrostatic properties of lipid monolayers. On hybridization the DNA desorbs from the surface of the lipid membrane, causing a substantial alteration of surface properties.

Adhesion of charged powders to a metal surface in the powder coating process

Substrate-particle adhesion of electrostatically charged, nonconducting particles deposited on electrically grounded substrates is discussed. Glass microspheres of diameters ranging from 25.5-74.1 /spl mu/m, charged by corona and tribe-charging, were deposited in a monolayer on conducting stannic-oxide coated surfaces of glass plates (NESA). The total force of adhesion due to electrostatic, van der Waals, and gravitational forces was measured by observing the removal of particles by applying a known electric field between the particle coated surface and a clean surface of a second NESA glass, placed parallel to it at a distance of 0.013 m. The adhesive force was measured as a function of particle size and charge. The net average charge on the particles was measured using a Faraday cup. The experimental values agree well with the calculated force of adhesion for a single layer deposition. The charge decay of the particles was studied using a noncontact electrostatic voltmeter. The charge relaxation time of the deposited powder was found to increase with time. A physical model of the adhesion of charged powder paints deposited on a grounded metal substrate is presented. The role of the forces acting on a spherical polymer particle deposited on the surface of a uniform coating of powder paint is investigated as a function of particle diameter and charge. The particles are assumed to be unipolarly charged and deposited uniformly on the substrate. The relative magnitudes of the electrostatic attractive and repulsive forces are analyzed as functions of powder film thickness and particle size.

Diurnal electrical potentials of plant leaves under natural conditions

Surface electrical potentials of leaves of beans ( Phaseolus vulgaris L.), cucumber ( Cucumis sativus L.) and cherry ( Prunus avium L.) were measured continuously and repeatedly over 3–4 day periods, mainly during fine weather. Potentials were monitored with a non-contacting electrostatic voltmeter. Leaves exhibited a diurnal rhythm of potentials with highest voltages after mid-day (+ 120 V max. recorded) and minimum potentials, near zero, at night. On dry, sunny days the polarity of leaves was consistently positive, at night polarity varied between neutral, positive and negative (− 30 V max.). Among the various weather factors examined that might influence leaf potentials, solar radiation and leaf surface temperatures were most intimately associated with electrical changes. Increases in leaf potentials could be detected within a few minutes of sunrise. Potentials were highest on hot, sunny days and lowest on overcast, cool days. Significant potential changes occurred when leaves were severed. Severance of leaves from plants growing in dry soil resulted in a rapid surge of leaf voltage (+) followed by a gradual decline. In contrast, severance of leaves from plants growing in flooded soil resulted in a reversal of polarity and a rapid increase in negative potential. When a severed leaf was electrically reconnected to the plant, its potential would revert back (approx.) to the level before severance. It was also discovered that when plants growing in dry soil were irrigated, leaf potentials increased rapidly. This study has revealed that there are significant patterns of diurnal variations of electrical potential of leaves under natural conditions. The reason for these changes is not understood.

The Langmur-blodgett monolayer dipole potential: a smeared dipole model for a lipid array, and pulsing of the potential by direct subphase infusion of immunochemical and lecti/polysaccharide complexes

An important contribution to the surface potential of lipid bilayers and monolayers comes from the intrinsic dipole moment of the lipid molecules. A theoretical model of the monolayer which involves a smeared dipole sheet approximation is introduced. This model is used to explore the nature and origins of the surface potential. In addition, the potential associated with phosphatidyl choline/cholesterol monolayers compressed on a Langmuir-Blodgett trough was measured with a non-contacting electrostatic voltmeter. A trough infusion configuration was fabricated to perform dynamic subphase experiments with compressed films in place. The potential/time response of monolayers to selective bimolecular systems such as antibody-antigen and concanavalin A-saccharide pairs was examined. These reactions induce spontaneous transients in dipole potential of magnitude 20–80 mV and duration of less than 1 s. The potential transients are attributed to local perturbation of lipid orientation and introduction of protein dipole fields caused by the formation of aggregates at the monolayer/water interface.

933 — Chemical modification of the bilayer lipid membrane biosensor dipolar potential

The bilayer lipid membrane (BLM) is an interesting model for a transducer, based on transmembrane ion current modulation by selective complexation of a membrane-embedded receptor with a suitable stimulant. The dipolar potential, which originates from the lipid bilayer headgroup zone, partially controls transmembrane ion current. Dipolar potentials associated with phosphatidyl choline/steroid lipid monolayers on a Langmuir-Blodgett thin-film trough have been measured with a non-contacting electrostatic voltmeter, and have been correlated with lipid chemistry. Lipid molecular interactions established by monolayer compression and BLM Arrhenius energy barriers determined from thermal dependence of ion conductivity of BLM have provided an evaluation of the dipolar potential with respect to its role in controlling ion current, surface ion adsorption and BLM structural integrity. Additionally, this work deals with the characteristics required for an optimum receptor-membrane system, which would best operate by dramatically influencing membrane fluidity/packing parameters as well as dipolar potential.

Electrostatic measurements of unusually large secondary pyroelectricity in partially clamped LiNbO3

Pyroeleetricity has been observed in single domain, single crystal LiNbO3 under partially clamped elastic boundary conditions using a non-contact electrostatic voltmeter. These boundary conditions were produced by the use of localized laser heating which generated a temperature change in the central 2.5 mm of a 19 mm diameter disk. These partially clamped boundary conditions give rise to (1) unusually large secondary pyroelectric effect in 2-cut crystals (the 2 or y axis perpendicular to the disk's face) whose components along the 1 and 3 axes map the radial and tengential components of the thermal stress, respectively and (2) surface and volume polarization which permit a partial experimental separation of primary and secondary pyroelectricity.