Electrostatic Voltmeter Research Articles

Noncontact measurement of electrostatic fields: Verification of modeled potentials within ion mobility spectrometer drift tube designs

The heart of an ion mobility spectrometer is the drift region where ion separation occurs. While the electrostatic potentials within a drift tube design can be modeled, no method for independently validating the electrostatic field has previously been reported. Two basic drift tube designs were modeled using SIMION 7.0 to reveal the expected electrostatic fields: (1) A traditional alternating set of electrodes and insulators and (2) a truly linear drift tube. One version of the alternating electrode/insulator drift tube and two versions of linear drift tubes were then fabricated. The stacked alternating electrodes/insulators were connected through a resistor network to generate the electrostatic gradient in the drift tube. The two linear drift tube designs consisted of two types of resistive drift tubes with one tube consisting of a resistive coating within an insulating tube and the other tube composed of resistive ferrites. The electrostatic fields within each type of drift tube were then evaluated by a noncontact method using a Kelvin-Zisman type electrostatic voltmeter and probe (results for alternative measurement methods provided in supplementary material). The experimental results were then compared with the electrostatic fields predicted by SIMION. Both the modeling and experimental measurements reveal that the electrostatic fields within a stacked ion mobility spectrometer drift tube are only pseudo-linear, while the electrostatic fields within a resistive drift tube approach perfect linearity.

An experimental study on the identification of delamination in a composite material by the passive electric potential CT method

When a piezoelectric film is glued on the surface of a structure member subjected to mechanical load, a distribution of electric potential is induced. In the existence of defects in the member, a characteristic variation of electric potential is observed. Based on this phenomenon, the passive electric potential CT (computed tomography) method is developed for detecting and identifying defects in a structure. In this study, the applicability of the passive electric potential CT method to the identification of a delamination in a CFRP laminate was experimentally examined. CFRP laminate specimens, which have an artificial interlaminer delamination, with a piezoelectric film on their surface were subjected to three-point bending. The electric potential distribution on the piezoelectric film was measured by a non-contact voltmeter. Characteristic variation reflecting the location and the size of the delamination is observed in the measured electric potential distributions. To identify the delamination, an inverse method was constructed based on the least-squares residual evaluated between the measured and computed electric potential distributions. The location and size of the delamination were estimated accurately. It was shown that the passive electric potential CT method using a piezoelectric film was useful for the quantitative identification of interlaminar delamination in laminated composite materials.

Monitoring of flowing charges with an electrostatic voltmeter

This paper describes a simple method of monitoring the net electric charge of powders transported pneumatically through a dielectric pipe. An electrostatic voltmeter (ESVM) is used to measure the voltage induced on an isolated ring electrode placed on the outside surface of the pipe. An equivalent circuit model of the measurement system was constructed and experimentally verified using an electrophotographic toner and an aluminum oxide powder (Al/sub 2/O/sub 3/). Knowledge of the voltage induced by flowing charged particles on the electrode allows for the calculation of the total charge that flew through the pipe. However, in order to obtain an accurate voltage measurement, the input impedance of the instrument used for that purpose must be very high. The high impedance of an ESVM makes it uniquely suited for this application.

Spectroscopic Measurement of Faint Light Produced by Rapid Separation of an Adhesive Tape

This paper describes results on an experimental study of faint light emission produced by separation of an adhesive tape from a glass or from a polymer film. Spectroscopic measurements of the faint light were carried out using a monochromator and a photomultiplier. The results indicated that the light emission was caused by discharges near the tape-air-glass triple junction. We found that the frequency of the light emission was strongly changed by changing the peeling speed of the tape. Discharge lights were detected in many times in the case of high-speed peeling, whereas no light was detected in the case of low-speed peeling. We also measured surface potential distributions on the film after separation from the tape using a XY-movable probe and an electrostatic voltmeter. The surface potential on the film after the fast-speed peeling became slightly higher than that on the film after the low-speed peeling.

Direct monitoring of the electrostatic charge of house-flies ( Musca domestica L.) as they walk on a dielectric surface

Charge build-up on walking Musca domestica was monitored in real time using an electrostatic voltmeter attached to an individual fly by a fine copper wire. Simultaneous video recording of behavioural movement was analysed by Inchworm ©. Charge accumulation by the fly moving on PVC was positive and directly proportional to distance walked; as a consequence the rate of charge accumulation was directly related to the walking speed. Plateauing (saturation) of charge was prevented from occurring due to the increased capacitance caused by the large amounts of conductive material attached to the flies and the short distances travelled. This technique also allowed the effect of small surface charges to be observed; a positively charged acetal surface caused a rapid positive charge increase relative to distance walked, while negative charges acted against the tribocharging and reduced rate of positive charge accumulation. This work provides important information about the relationship between insect behaviour and charge accumulation with implications for the development and design of novel control strategies utilising electrostatic powders to adhere to the charged surfaces of insects or other organisms.

Charging of Insulating Glass Caused by Contact with Plates

In the fabrication of electronic products, charging of glass substrate induced in separation process is probable to cause the electrostatic discharge to the devices. We measured the charging potential of glass substrate which was separated from a plate, by using an electrostatic voltmeter. From the experiment, we obtained the following results. The contact electrification potential of glass substrate was dependent on the material of the plate. This phenomenon was related to their effective work functions. Furthermore, the charge quantity on glass depended on the number of contact with the plate and was higher in the smooth surface than in the rough surface.

On the electrostatics of pneumatic conveying of granular materials using electrical capacitance tomography

In this work the electrostatics of the pneumatic conveying of granular materials in a non-conducting (PVC) pipe is studied using Electrical Capacitance Tomography (ECT) system. The non-conducting wall in general attains static charges arising from particle-wall collisions in the initial periods of conveying process and then reaches equilibrium with the surroundings. The polarity of particles and conveying pipe inner wall agrees reasonably well with the contact potential difference measurements. The perturbations in the capacitance signal due to charge accumulation are larger with smaller air superficial velocity. The denser flow regimes give larger wall residual charge. Wall charging process shows similar trend described by surface potential taken from electrostatic voltmeter to that revealed by ECT measurements. Also the addition of small amount (0.5% by weight) of anti-static agent (Larostat-519) in the powder form decreases the electrostatic charge generation by altering the dynamics of particle–particle and the particle–wall collisions.

Stress intensity factor measurement of cracks using piezoelectric element

A stress intensity factor (SIF) measurement method for cracks using a piezoelectric element and an electrostatic voltmeter is presented. In this method, an isotropic piezoelectric element is first attached near the tip of the crack. Then surface electrodes are attached to three different positions on the piezoelectric element. The electric potentials of the surface electrodes, which are proportional to the sum of the stress (σ x + σ y ) on the structural member, are measured by an electrostatic voltmeter during load cycling. The mode I and mode II SIFs of the crack are estimated using the relationship between the SIF and (σ x + σ y ). The applicability of the proposed method is examined through experiments and numerical analysis.

Stress intensity factor measurement of cracks using a piezoelectric element

We present a stress intensity factor (SIF) measurement method of cracks using a piezoelectric element and electrostatic voltmeter. In the method, an isotropic piezoelectric element is first adhered near the crack tip. Then, the surface electrodes are attached to the three different positions on the piezoelectric element. The electric potentials of the surface electrodes, which are proportional to the strain sum (ɛx+ɛy) on the structural member, are measured by an electrostatic voltmeter during load cycling. Mode I and mode II SIFs of the crack are estimated using the relationship between the SIF and (σx+σy). The applicability of the proposed method is examined through experiments and numerical analysis.

Measurement of electric charges on flowing toner with an electrostatic voltmeter

In every electrophotographic development system, the optimal charging and mass transfer processes are crucial for achieving high quality prints. Therefore, precise measurements of both charge and mass of toner become very important. This paper presents a novel method for measurements of the electric charge of the flowing electrophotographic toner particles. An electrostatic voltmeter (ESVM) is used for precise measurements of the voltage induced by charges carried by the flux of solid toner particles and by the charges generated on the walls of a dielectric pipe, while the toner is pneumatically transported through the pipe. Additionally, the total charge and mass of the toner are measured before and after passing through the pipe. In this way, voltages registered by the ESVM can be correlated with the amount of charge created by tribocharging. This allows for determination of tribocharging properties of the toner at a given particle flow velocity and for a given dielectric pipe material. The ESVM is a convenient, noncontacting, continuous, real-time charge monitoring tool.

Generation mechanism of residual clamping force in a bipolar electrostatic chuck

Clamping and residual clamping forces of a Johnsen–Rahbek-type (JR-type) bipolar electrostatic chuck (ESC), which has electrically independent dual electrodes, were measured. Area ratios of the ESC’s two electrodes ranged from 1 to 4.6. It was found that the clamping force per unit area decreases with increasing area ratio and that the residual clamping force per unit area increases with increasing area ratio. To reveal the mechanism of residual clamping force, an equivalent circuit model of a JR-type bipolar ESC was devised. The model showed that the residual clamping force is caused by the residual charge that results from the charge difference in two monopolar ESCs. The charge difference is due to the resistance dependency on voltage of the dielectric layer of the ESC. The wafer voltage calculated from the model agreed well with the voltage measured by an electrostatic voltmeter. It can be concluded that the model is suitable for simulating the performance of a bipolar ESC.

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.

Electrostatic charge and field sensors based on micromechanical resonators

We have developed highly sensitive electrometers and electrostatic fieldmeters (EFMs) that make use of micromechanical variable capacitors. Modulation of the input capacitance, a technique used in macroscale instruments such as the vibrating-reed electrometer and the field-mill electrostatic voltmeter (ESV), moves the detection bandwidth away from the 1/f-noise-limited regime, thus improving the signal-to-noise ratio (SNR). The variable capacitors are implemented by electrostatically driven resonators with differential actuation and sensing to reduce drive-signal feedthrough. The resonators in the electrometer utilize a balanced comb structure to implement harmonic sensing. Two fabrication methods were employed - a hybrid technology utilizing fluidically self-assembled JFETs and SOI microstructures, and an integrated process from Analog Devices combining 0.8-μm CMOS and 6-μm-thick polysilicon microstructures. All devices operate in ambient air at room temperature. Measured data from one electrometer with an input capacitance of 0.7 pF indicates a charge resolution of 4.5 aC rms (28 electrons) in a 0.3 Hz bandwidth. The resolution of this electrometer is unequaled by any known ambient-air-operated instrument over a wide range of source capacitances. The EFM has a resolution of 630 V/m, the best reported figure for a MEMS device.

Visualization of back surface defects by piezoelectric film

The surface strain distribution of a plate can be measured from the electric potential on the piezoelectric film mounted on it. When the plate with a back surface defect is deformed, the resultant strain distribution on the front surface reflects the size and the shape of the defect. Instead of measuring the electric potential by the electrostatic voltmeter, this paper attempts to visualize the strain distribution by means of absorption of charged polymer powder to the piezoelectric film. And also attempting this method to the various size of the defect, resolution of detecting the defects is discussed by the experiment.

612 受動型電気ポテンシャル CT 法による三次元表面き裂の同定に関する実験的検討

When a piezoelectric film is glued on the surface of a cracked structure subjected to load, change in distribution of electric potential is observed on the surface of piezoelectric film. Based on this phenomenon, the passive electric potential CT (computed tomography) method was developed for identifying two- and three-dimensional cracks. In this study, this method was applied to identify experimentally a three-dimensional crack opening on the back surface. Electric potential distribution on the piezoelectric film mounted on the front surface was measured by non-contact voltmeter. Measured electric potential distribution agreed well with that calculated by the FEM. The inverse method based on the least residual method was applied for estimating the location and size of crack from the measured electric potential distribution. It was shown that the passive electric potential CT method using piezoelectric film was useful for quantitative identification of back-surface three-dimensional crack.

Application of PVDF Film to Stress Measurement of Structural Member

In this paper a method to measure stress distribution using PVDF film and electrostatic voltmeter of non-contact type is developed. PVDF film is well suited to strain sensing applications for its excellent sensitivity and other good properties. The stress and strain distributions are determined from the measured potentials taking into account the piezoelectric constitutive law of film materials. First, in this paper the relationship between the electric potential and stresses is deduced in detail. Then, parameters used in the electric potential-stress relationship are estimated by an experiment applying the PVDF films to a smooth plate specimen. Next, a method to make isotropic piezoelectric material and a method too amplify the electric potential of the PVDF film by laminating two or more PVDF films together are also introduced and validated by experiment. Last, in order to check the accuracy of PVDF film as a stress measurement sensor, an experiment to measure the stress distribution of a plate specimen with an inclined crack is performed. The experimental results are in good agreement with those obtained from numerical calculation.

232 試験片表面に接合したピエゾ材膜の非接触電気ポテンシャルCT計測によるき裂同定(OS6-7 超音波・赤外線・圧電フィルム)(OS6 実験力学の新展開)

Piezoelectric film is a sensing element that generates an electrical charge proportional to a change in mechanical stress. When the piezoelectric film is glued to the surface of a cracked material subjected to varying load, periodic change in distribution of electric potential is observed on the surface of piezoelectric film. Based on this phenomenon, the passive electric potential CT (computed tomography) method was developed for identifying two- and three-dimensional cracks. In the previous study, contact measurement method using electrodes and voltmeter was applied. In the present study, electric potential distribution is measured by non-contact voltmeter, which may be suitable for multi-point measurement, to develop non-contact electric potential CT measurement. It was found that the non-contact electric potential CT measurement had improved resolution and accuracy in crack identification.

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.

Measurement of Static Strain Distribution Using Piezoelectric Polymer Film. Principle and Application to a Holed Plate.

The objective of the present study is to exploit the feasibility of piezoelectric polymer film sensors to evaluate in-plane static strain distributions of structural components. In contrast to ordinary use of piezoelectric films as strain and strain-rate sensors detecting electric charges or currents in a closed circuit, the proposed strategy consists of directly measuring the distribution of electric potentials induced in the piezoelectric film mounted on the surface of a deforming structural component. Strain distributions are determined from the measured potentials taking into account the piezoelectric constitutive law of the film material. As an illustrative example, thin films of polarized polyvinylidene fluoride (PVDF) are mounted on a holed elastic plate subjected to in-plane loading, and the induced potential distributions are measured on the film surface by an electrostatic voltmeter. It is demonstrated that the determined strain distributions are in fair conformity with those predicted by the theory of linear elasticity.

Measurement of Static Strain Distribution Using Piezoelectric Polymer Film. Principle and Application to a Holed Plate.

The objective of the present study is to exploit the feasibility of piezoelectric polymer film sensors to evaluate in-plane strain distributions of structural components. In contrast to ordinary use of piezoelectric films as strain and strain-rate sensors detecting electric charges and currents through electrodes, the proposed strategy consists of directly measuring the distribution of electric potentials induced in the piezoelectric film mounted on the surface of a structural component in loading. The stress and strain distributions are determined from the measured potentials taking into account the piezoelectric constitutive law of film materials. As an illustrative example, thin films of polarized polyvinylidene fluoride (PVDF) are mounted on a holed elastic plate subjected to in-plane loading, and the induced potential distributions are measured on the film surface by an electrostatic voltmeter of non-contact type. It is demonstrated that the determined strain distributions are in fair conformity with those analytically predicted.