Electrostatic Sensor Research Articles

Measurement of velocity and concentration profiles of pneumatically conveyed particles in a square-shaped pipe using electrostatic sensor arrays

Cross-sectional measurement of particle velocity and concentration in a pneumatic conveying pipe is desirable for the characterisation of particle flow dynamics and determination of particle mass flow rate. In this study, an inner-inserted electrostatic sensor array consisting of nine pairs of electrodes is implemented to measure the cross-sectional velocity and concentration profiling of particles over the whole cross section in a square-shaped pipe. Experimental tests were conducted on both vertical and horizontal pipe sections on a test rig under dilute conditions with different air velocities and particle mass flow rates. Test results show that the slope-shaped particle concentration profile changes to an arch-shaped one when the particles flow from a horizontal pipe to a vertical one. The particle velocity profile is arch-shaped in both vertical and horizontal pipes. A comparative study of cross-sectional mean particle velocity and concentration measured by the developed electrostatic sensor arrays is conducted.

Flame Boundary Measurement Using an Electrostatic Sensor Array

The flame boundary is an important geometrical characteristic for the evaluation of flame properties such as heat release rate and radiation. Reliable and accurate measurement of the flame boundary is desirable for the prediction of flame structure and the optimization of combustion systems. Such measurement will inform the designers and operators of the combustion systems. This article presents for the first time a study of using an electrostatic sensor array for flame boundary measurement. The electrostatic sensor is placed in the vicinity of the flame to sense its movement through charge transfer. The principle, design, implementation, and assessment of a measurement system based on this methodology are introduced. Comparative experimental investigations with a digital camera conducted on a laboratory-scale combustion test rig show that the electrostatic sensor can respond to the variation of the distance between the electrode and the flame boundary. Reconstruction of the flame boundary is achieved using a set of distance measurements obtained from a sensor array. For diffusion flames over the range of fuel flow rate 0.60-0.80 L/min and premixed flames over the range of equivalence ratio 1.27-3.81, experimental results show that the measurement system is capable of providing a reliable measurement of the flame boundary. The correlation coefficients under all test conditions are mostly larger than 0.96, the mean relative errors within 7.4%, and the relative root-mean-square errors within 0.09. More accurate flame boundary measurements are achieved for diffusion flames. In addition, the overall polarity of charges in a flame can be determined from the polarity of the sensor signal.

A unified model for electrostatic sensors in fluid media

We present a unified model of electrostatic sensors comprising cantilever microbeam resonators in fluid media. The model couples Euler–Bernoulli beam equation to the nonlinear Reynolds equation. Static, damped eigenvalue, and dynamic reduced-order models were developed and validated by comparing a nonlinear frequency response of a gas sensor to its experimentally measured counterpart. Experiments were conducted to verify the capability of the developed model to predict the out-of-plane and in-plane natural frequencies of the sensor. The models were also used to investigate the potential operation of electrostatic chemical sensors based on different sensing mechanisms. While in-plane and out-of-plane vibration modes were found to be viable alternatives for resonant gas sensors, only in-plane modes were suitable to implement resonant chemical sensors due to the added mass and damping of liquid media. Similarly, higher-order modes were found more sensitive than lower order modes. Further, evidence was found for elastic interaction between out-of-plane modes and liquids in the channel underneath them but none for in-plane modes. Finally, the model predicts that in-plane modes provide the multi-valuedness necessary to implement bifurcation chemical sensors in liquid media.

Cross-Correlation Sensitivity-Based Electrostatic Direct Velocity Tomography

Electrostatic tomography (EST) has been widely used in gas–solid two-phase flows to measure particle velocity in many industrial processes. However, EST is a passive measurement technique, and this results in rare independent measurements compared with other tomographic modalities. In this article, an electrostatic direct velocity tomography (EDVT) method is proposed to increase the number of independent measurements and to improve the accuracy of velocity estimation. For a two-plane electrostatic sensor, the cross-correlation (CC) velocities between the electrodes from the two planes at different circumferential positions can represent the particle velocities in different regions. First, the CC velocities between the electrodes on different planes are calculated and used as new measurements. In this way, the number of independent measurements of a 16-electrode EST sensor can be easily increased from 16 to 120. Second, by analyzing the relationship between the CC velocities and the particle charge and particle velocity distribution, a CC sensitivity matrix is established. Finally, a tomographic model to represent the velocity distribution of charged particles can be established based on the new measurements and the CC sensitivity matrix. Simulation and experimental results show that the velocity distribution reconstructed by EDVT can represent the particle velocity distribution in the pipeline and is promising to provide a method to study the mechanism of gas–solid two-phase flows.

Investigations into the blockage of pulverized fuel pipes on coal-fired boilers using an electrostatic sensor system

The blockage of pulverized fuel (PF) conveying pipes on a coal-fired power plant is a hazard accident. An in-depth understanding of the factors that cause PF pipe blockage provides operators with prior knowledge to avoid such accidents. Two representative primary air pipe blockage events are observed on two commercial boilers, respectively. The PF dynamic parameters of the two cases during the whole blockage processes are monitored by an electrostatic sensor array based instrumentation system. The variation trends of the velocity, mass flow rate, volumetric concentration and flow stability of PF particles in different blockage stages are described in detail. The main reasons for the two blockage events are analyzed based on the geometry of the PF conveying pipes and the dynamic parameters of the PF particles. The results obtained show that on-line monitoring of PF flow is an effective and reliable way for the early detection of PF pipe blockage.

A Method for Measuring the Height of Hand Movements Based on a Planar Array of Electrostatic Induction Electrodes.

This paper proposes a method based on a planar array of electrostatic induction electrodes, which uses human body electrostatics to measure the height of hand movements. The human body is electrostatically charged for a variety of reasons. In the process of a hand movement, the change of a human body’s electric field is captured through the electrostatic sensors connected to the electrode array. A measurement algorithm for the height of hand movements is used to measure the height of hand movements after the direction of it has been obtained. Compared with the tridimensional array, the planar array has the advantages of less space and easy deployment; therefore, it is more widely used. In this paper, a human hand movement sensing system based on human body electrostatics was established to perform verification experiments. The results show that this method can measure the height of hand movements with good accuracy to meet the requirements of non-contact human-computer interactions.

Particle velocity measurement of binary mixtures in the riser of a circulating fluidized bed by the combined use of electrostatic sensing and high-speed imaging

The flow dynamics of binary particle mixtures in the fluidized bed needs to be monitored in order to optimize the related industrial processes. In this paper, electrostatic sensing and high-speed imaging are applied to measure the velocities of polyethylene and sand particles in the binary particle mixtures in fluidization. Experimental studies were conducted on a lab-scale cold circulating fluidized bed. Correlation function between electrostatic signals from upstream and downstream electrodes placed along the riser shows two peaks that represent transit times for the two types of particles. To verify the above results, high-speed imaging was adopted to capture the flow images of particle mixtures. Particle Image Velocimetry and Particle Tracking Velocimetry algorithms were utilized to process the resulted images in order to measure the velocities of polyethylene and sand particles. The reasons for two-peak correlation functions are illustrated based on the frequency spectrums of the mono-solid-phase electrostatic signals and the velocity difference between polyethylene and sand particles. Finally, comparisons on the velocities obtained from electrostatic sensing and high-speed imaging demonstrate the electrostatic sensor can roughly estimate the particle velocity of binary particle mixtures in the near wall region of the circulating fluidized bed.

IC 741 a nd IC AMP02FP Based Signal Conditioning Circuit f or Electrostatic Sensor u sing Multisim

The Electrostatic sensors are extensively used in military, radar and electronic applications which can sense the electric charge from the moving charged motes. The signal conditioning circuit for an electrostatic sensor is a voltage amplifier that can intensify a small input signal. This paper proposal is to design a low noise signal conditioning circuit using Multisim and to study the performance of its gain, bandwidth and noise properties.

Design of charge-sensitive and current-sensitive preamplifiers for electrostatic sensor

In this paper, the signal shape similarity degree is defined as quantitative criteria to distinguish charge-sensitive or current-sensitive preamplifier of electrostatic sensor. To establish the relationship between the similarity degree and the preamplifier, the rate (k) of the cutoff frequency of the preamplifier to the highest frequency of the induced current signal is presented. It is found that there are monotonic relationships between the similarity degree and k, which are built and used to design charge-sensitive and current-sensitive preamplifiers with different requirements. The results of the single particle free-fall experiment verify the effectiveness of this method.

Improvement of spatial sensitivity of an electrostatic sensor for particle flow measurement

The ring-shaped electrostatic sensor is a typical particulate flow measurement system, which suffers from flow profile dependency due to its non-uniform spatial sensitivity. In this paper, a method based on sensor's output power frequency spectrum is proposed, which can be realized by repeatedly decomposing the sensor's overall output power spectrum to identify elementary frequency spectra corresponding to equivalent flow streams. The decomposed components can then be re-weighed to improve the uniformity of spatial sensitivity. This is a low cost approach, and there is no need to modify simple structure of the current sensor.

Investigation into position deviation effect on micro newton force sensor

The position deviation effect on force sensor with a resolution of micro newton scale was investigated by theory model analysis and numerical simulation method. The finite element method and theoretical model were used to analyse the influence of the electrostatic micro force sensors when the electrode position of the cylindrical capacitor changed. Relationship between the sensor output micro force and the position deviation of the internal electrode in the cylindrical capacitance was obtained. It was found that different position deviation form had different degrees of influence on the sensor’s output result and the regions with little effect by position deviation were existed. For translation along Z-axis, the region was [-4 mm, 14 mm]. For translation along r-axis, the region was [-0.2 mm, 0.2 mm]. And for rotation around r-axis, the region was [-1°, 1°]. The corresponding maximum errors of the micro force output were 1.49%, 2.09% and 2.20%, respectively.

Electrostatic Sensor for Determining the Characteristics of Particles Moving From Deposition to Suspension in Pneumatic Conveying

The minimum conveying velocity or the lowest point of pressure drop curve can reflect the characteristics of particles moving from deposition to suspension in pneumatic conveying. However, when the mass flow rate is low, the change of particles flow cannot be effectively reflected by the above methods. In this paper, based on a 4-arc electrode electrostatic sensor, with localised sensitivity, the detailed scale signals that represent the particle random motion are extracted by the combination of Empirical Mode Decomposition (EMD) and Hurst exponent. The differences in the particle random motion energy ratio (PRMER) of 4-channel electrode signals are used to characterize the transition of flow state. In the verification experiment by using a belt-style electrostatic velocity measured rig, the higher the velocity of rubber belt or the closer to the electrode, the higher the PRMERs of electrostatic signal. In the experiment of gas-solid two-phase flow rig, the PRMERs of 4-channel electrode signals are all increasing with the increase of superficial gas velocity, and the PRMERs of different electrodes are rather different at low superficial gas velocity ( ${V}_{g}$ ). When ${V}_{g}$ drops at the minimum pressure drop point ( ${P}_{{MPD}}$ ), the PRMERs of top/bottom and left/right electrodes begin to separate (e.g. the particle mass flow rates are 100 kg/h and 120 kg/h). Furthermore, when the solid mass flow rate is 80 kg/h, the proposed method can clearly characterize the transition of flow states in the pipeline, but the pressure drop phase diagram cannot.

Formation of PANI-PVA salt via H-bonding between PVA and PANI: Aqueous coating for electrostatic discharge, sensor and corrosion applications

This work aims to make environmentally friendly coating consists of an aqueous dispersion of conducting polyaniline (PANI) salt containing H2SO4 and PVA dopants in polyvinyl alcohol (PVA) for electrostatic discharge, sensor and corrosion applications. Aniline is oxidized by ammonium persulfate to PANI-sulfate salt (PANI-SA) without using any protic acids, wherein, sulfuric acid generated from ammonium persulfate during the oxidation of aniline gets doped on to PANI system. The results of PANI-SA are compared with (i) PANI-H2SO4 salt prepared in presence of sulfuric acid in the aniline polymerization and (ii) PANI salt containing dopants of H2SO4 and PVA, (PANI-SA-PVA), prepared with polymeric alcohol, PVA, instead of hazardous sulfuric acid, in the polymerization of aniline. Yield, conductivity, density, diffraction pattern, morphology and thermal properties of PANI-SA are more or less similar to that of the PANI-SA-PVA system. However, yield and conductivity of PANI-H2SO4 are higher than that of PANI-SA-PVA due to the increase of oxidizing efficiency by H2SO4. These three salts, PANI-SA, PANI-H2SO4 and PANI-SA-PVA are dissolved in aqueous PVA. These dispersions are coated on (i) glass slide to find the hydrophilic nature (ii) transparent polyethylene terephthalate film for ESD application, (iii) ceramic tube for sensing ammonia gas, and (iv) stainless steel plate for corrosion study. Among the three PANI salts, PANI-SA-PVA dispersed in PVA shows better performance.

Software and hardware complex for monitoring the ion beam parameters of a particle accelerator

This paper presents the development of an integrated system for monitoring the position of the ion beam in a particle accelerator. The effect of external disturbances and the imperfection of the accelerators themselves lead to the distortion of the ion beam trajectory in a cyclotron; therefore, constant monitoring and correction of the beam position is necessary. To control and correct the distortion of the ion beam trajectory in a cyclotron, an electrostatic sensor based on a pickup electrode is used as a meter. One of the features of the developed meter is that the estimation is carried out according to the second harmonic of the signal, allocated on a band-pass filter. This is due to the fact that during the accelerator work a large amount of noise is induced on pickup electrodes and the noise level at the fundamental frequency is high. The hardware and software complex converts the measured data obtained from the sensors, such as the transverse distribution of the beam energy, the beam current and the coordinates of its center of mass into an electrical signal, followed by their sampling in an analog-to-digital converter and the transmission of the measurement results through standard communication protocols and further processing in the LabView software. Using the received signals, the beam parameters such as the length of the ion bunch, the vertical beam position, and the acceleration phase are calculated for the corrector.

Electrostatic induced charge signal extraction based on waveform characteristic in time domain

The measurement signal from the inner flush-mounted electrostatic sensor includes both induced charge signal and transferred charge signal. The extraction of induced charge signal from the mixed signals is of great significance to the solid phase velocity measurement. In this paper, a method of extracting induced charge signal based on the waveform characteristic in time domain is proposed. In the calibration experiment of the belt-style electrostatic velocity measurement rig, the mean absolute percentage error and the mean relative standard deviation (1.30%/1.01%) are lower than the direct cross-correlation method (4.81%/5.71%) and the Empirical Mode Decomposition (EMD-based) method (2.55%/2.38%), moreover, the average signal-to-noise ratio (SNR) of the proposed method is the greatest. In the experiment of gas-solid two-phase flow rig, the average correlation coefficient and the mean relative standard deviation are 0.77 and 2.46%, which are better than the direct cross-correlation (0.48/2.87%) and the Discrete Wavelet Transform (DWT) (0.74/2.69%).

Design optimization of electrostatic sensor electrodes via MOPSO

An ideal electrostatic sensor with optimized electrodes is required for solid particles (SPs) velocity determination. The simplicity and reliability of the multi-objective particle swarm optimization (MOPSO) imparted further impetus to the accurate determination of SPs velocity using electrostatic sensors. This paper reports a new design of electrostatic sensors via MOPSO, where the sensors geometry is determined using response surface methodology (RSM). Besides, electrode sensing factors including spatial sensitivity and statistical error of electrostatic sensors are considered for the optimization. Parameters such as electrode dimensions, velocity, and distribution of particles in the pipeline are found to greatly influence the electrodes sensing performance. Electrodes with different physical sizes were applied to find their optimal value to attain minimum statistical error and maximum spatial sensitivity, which were optimization targets. Following RSM and MOPSO methods, an electrode’s optimum length of 0.6 cm and thickness of 0.5 cm has been achieved. It is established that the electrodes spatial sensitivity distribution appears uniform due to their size optimization. Furthermore, very thin electrodes with short length are determined to be prerequisite for sensitivity enhancement. Present study finds a theoretical basis for the electrostatic electrodes optimal design.

Electromechanical behavior of graphene foams

Graphene foam (GF)—a three-dimensional porous structure that comprises several graphene layers—has excellent physical properties and, consequently, exciting possible applications. In this work, we report the mechanical behavior of GFs that were grown using high-temperature chemical vapor deposition (CVD) and subjected to electrostatic tensile loads. We show that such loads reduce the mechanical stiffness of the GF (Young's modulus in the kilo-Pascal range) and release prestresses generated during growth. In addition, GF demonstrates electrostatic resonance. By characterizing the fundamental electromechanical behavior of GF, this Letter paves the way toward the development of novel GF-based devices, such as GF electrostatic resonant sensors, flexible capacitors, and micro- and nanoelectromechanical devices.

Reweighting Signal Spectra to Improve Spatial Sensitivity for an Electrostatic Sensor.

The ring-shaped electrostatic sensor is a gas–solid flow measurement system, which has a problem of flow profile dependency. To deal with this problem, a method was introduced in this paper, which was to repeatedly use the successive “tails” of the sensor’s overall output power spectrum to identify elementary frequency components corresponding to the equivalent roping flow streams. From the radial locations of these equivalent flow streams, the decomposed power frequency spectral components were then reweighted accordingly. Through such signal processing, an improved electrostatic sensor spatial sensitivity was achieved without modifying the sensor’s structure. The method of interpolation was presented and discussed, and the effect of velocity profile on the proposed method was evaluated under different velocity profiles.

Design of embedded electrostatic sensors for the RFX-mod2 device

The RFX-mod experiment is currently undergoing a challenging upgrade of the machine assembly. One of the main purposes of RFX-mod2, the upgraded device, is the achievement of better performances by decreasing the tearing modes amplitude in Reversed-Field Pinch (RFP) configuration thanks to a higher plasma-shell proximity. Moreover, most of the innovations characterizing the device and its diagnostics are conceived with the aim of operating as both RFP and tokamak. These different configurations are taken into account in the electrostatic sensors design and layout. RFX-mod2 will be equipped with poloidal and toroidal arrays of electrostatic probes, measuring plasma density and temperature, plasma potential, particle and energy fluxes and floating potential fluctuations. Two toroidal arrays of 72 probes each (one on the high field side and one on the low field side), along with four poloidal arrays of 28 elements, are foreseen. Such a large amount of sensors is due to the requirement of a better characterization of the numerous instabilities observed in the RFP plasma edge, with the possibility to study the plasma shape in different tokamak configurations (circular, single null, double null). Three different kinds of Langmuir probe configurations will be installed: single probes, 5-pin balanced triple probes and ball-pen probes. The conceptual design of the sensors takes inspiration from the model successfully installed on RFX-mod, that allows the removal of tiles in case of damage, by means of a remote handling manipulator.

Research of electrostatic field measurement sensors

Due to the discharge of static electricity, the force of static electricity and the phenomenon of electrostatic induction, it poses a major safety hazard for on-site operations personnel and equipment, resulting in significant losses and hazards. When people work on site, they can't intuitively know whether there is static electricity and quantify the static charge on the device. Therefore, this article describes the design principle of the sensor in the electrostatic field measurement in detail. In this paper, theoretical analysis and simulation analysis are carried out for two different working modes of variable-area and variable-pitch sensors. The experimental results verify the measurement principle of the vibration capacitor sensor, and the MEMS electric field sensor is also described in detail. This paper analyzes and summarizes the characteristics of existing electrostatic field measurement sensors at home and abroad in order to select reference for electrostatic field measurement sensor design and actual scene measurement operations.