Mathematical modelling and experimental validation of electrostatic sensors for rotational speed measurement

Recent research has demonstrated that electrostatic sensors can be applied to the measurement of rotational speed with excellent repeatability and accuracy under a range of conditions. However, the sensing mechanism and fundamental characteristics of the electrostatic sensors are still largely unknown and hence the design of the sensors is not optimised for rotational speed measurement. This paper presents the mathematical modelling of strip electrostatic sensors for rotational speed measurement and associated experimental studies for the validation of the modelling results. In the modelling, an ideal point charge on the surface of the rotating object is regarded as an impulse input to the sensing system. The fundamental characteristics of the sensor, including spatial sensitivity, spatial filtering length and signal bandwidth, are quantified from the developed model. The effects of the geometric dimensions of the electrode, the distance between the electrode and the rotor surface and the rotational speed being measured on the performance of the sensor are analyzed. A close agreement between the modelling results and experimental measurements has been observed under a range of conditions. Optimal design of the electrostatic sensor for a given rotor size is suggested and discussed in accordance with the modelling and experimental results

A new method to optimize geometric design of electrostatic sensor electrodes using particle swarm optimization

Optimization of electrostatic sensor electrodes plays a significant role to achieve more homogenous spatial sensitivity. Particle swarm optimization (PSO) is a simple method that has attracted many attentions in recent years. In this paper, the physical sizes of several electrodes for electrostatic sensors are optimized using the PSO technique. Spatial sensitivity of electrode is considered as objective function in this method. Additionally, the thickness and length of electrode are described as physical characteristics of electrode, which need to be optimized. In order to verify this optimization method, different electrodes are applied in laboratory. The optimal value of thickness and length of electrode according to the optimization and experimentation are 5mm and 6mm, respectively. As a result, there is a great agreement between the optimization and experimental results

Particle size measurement using electrostatic sensor through spatial filtering method

Particle size measurement is important in powder and particle industries in which the particle size affects the productivity and efficiency of the machine, for example, in coal-fired power plants. An electrostatic sensor detects the electric charge from dry particles moving in a pipeline. Analysis of the detected signal can provide useful information about the particle velocity, mass flow rate, concentration and size. Using electrostatic sensors, previous researches studied particle sizing using magnitude dependent analysis which is a highly conditional method where the results can be affected by other parameters such as particle mass flow rate, velocity and concentration. This research proposes a magnitude independent analysis for particle sizing in the frequency domain called spatial filtering method. The solution was started by modeling and analysis of the charge induced to the ring electrode using finite-element analysis to find the sensitivity of electrode. A mathematical model was provided to compute particle position on the radial axis of the electrode and then a new technique was proposed to extract a single particle size from the calculated particle radial position. To validate the proposed method experimentally, a sensor was designed and five test particles ranging from 4 mm to 14 mm were selected for measurement. The results show a 0.44 mm estimation error between the estimated and expected results. The results also show that the method is promising for the establishment of a reliable and cost-effective solid particle sizing system

Analysis of the Detection of Organophosphate Pesticides in Aqueous Solutions Using Polymer-Coated Single IDT Sensors

The single interdigital transducer (IDT) device was investigated as a micro-chemical sensor for the detection of organophosphates compounds in aqueous solutions. The compounds of interest are: parathion, parathion-methyl, and paraoxon. The polymers used as a partially-selective coating for the direct detection of these compounds are 2,2\u27-diallylbisphenol A- 1,1,3,3,5,5-hexamethyltrisiloxane (BPA-HMTS) and polyepichlorohydrin (PECH). BPA-HMTS is synthesized here at Marquette University. The measurement of interest for the single IDT is the change radiation resistance. The radiation resistance represents the energy stored in the propagating acoustic wave. As analyte absorbs into the polymer coating, changes in the film\u27s properties will undergo resulting in a change in the radiation resistance i.e the acoustic wave properties. The film\u27s properties changing include: added mass, viscoelastic properties, thickness, and dielectric properties. These properties will contribute to an overall change in the radiation resistance. A linear change in the radiation resistance is expected to occur for increasing concentrations of an organophosphate. The experimental results indicate that BPA-HMTS shows greater sensitivity towards the organophosphates than PECH. Both polymers showed greatest to lowest sensitivity to parathion, parathion-methyl, and paraoxon respectively. Thicker films tested for both polymers, 0.75μm thick, show a higher response due to a more pronounced effect of mass loading than the thinner films tested, 0.50μm. The response times for BPA-HMTS were much faster than for PECH. Both films showed fastest to slowest response time to paraoxon, parathion-methyl, and parathion respectively. The sensor is tested for reproducibility for the polymer BP-HMTS. A sensor array consisting of separately tested devices from this work as well as work done by a previous student is utilized to increase the selectivity of the three organophosphates. Radial plots are performed for each organophosphate and concentration using the change in radiation resistance, response time, and frequency shift for both BPA-HMTS and PECH at 0.50μm as input parameters. These plots yield unique recognition patterns for each organophosphate that can be used to distinguish one from another

A review of electrostatic monitoring technology: The state of the art and future research directions

Electrostatic monitoring technology is a useful tool for monitoring and detecting component faults and degradation, which is necessary for system health management. It encompasses three key research areas: sensor technology; signal detection, processing and feature extraction; and verification experimentation. It has received considerable recent attention for condition monitoring due to its ability to provide warning information and non-obstructive measurements on-line. A number of papers in recent years have covered specific aspects of the technology, including sensor design optimization, sensor characteristic analysis, signal de-noising and practical applications of the technology. This paper provides a review of the recent research and of the development of electrostatic monitoring technology, with a primary emphasis on its application for the aero-engine gas path. The paper also presents a summary of some of the current applications of electrostatic monitoring technology in other industries, before concluding with a brief discussion of the current research situation and possible future challenges and research gaps in this field. The aim of this paper is to promote further research into this promising technology by increasing awareness of both the potential benefits of the technology and the current research gaps

Optimization of electrostatic sensor for velocity measurement based on particle swarm optimization technique

Electrostatic sensors are broadly applied to measure velocity of solid particles in many industries because controlling the velocity particles improves product quality and process efficiency. These sensors are selected due to their robust design and being economically viable. Optimization of different electrode sizes and shapes of these sensors is required to find the ideal electrodes associated with maximum spatial sensitivity and minimum statistical error. Uniform spatial sensitivity is a crucial factor because it would lead to increase similarity between the measured correlation velocity and true mean particle velocity. This thesis proposes a new method to optimize different parameters of electrodes for electrostatic sensors. This technique identified characteristics of the electrostatic sensor in a MATLAB code called Particle Swarm Optimization (PSO). A mathematical model of various electrodes to compute spatial sensitivity and statistical error was applied to extract geometric size information of electrodes to detect suitable equations. To validate the proposed method, different values of electrode designs were applied in experimental tests conducted in a laboratory to measure the velocity of solid particles. The experimental results were optimized through Response Surface Methodology (RSM), an optimization technique for experimentation. The optimized results showed that spatial sensitivity of circular-ring electrode is more uniform in comparison to the other electrodes. The optimal length of circular-ring electrode was between 0.577 cm and 0.600 cm. In addition, the best thickness for the electrodes was between 0.475 cm and 0.500 cm. A close agreement between optimization and experimentation verifies that the proposed method is feasible to optimize physical sizes of electrostatic sensor electrodes. These results provide a significant basis of the effect of geometric dimensions on the sensing characteristics of electrostatic sensors

Environmental and medical applications of molecularly imprinting polymer sensor for the detection of progesterone

Molecularly imprinted polymers are spatial technique with artificial recognition sites compatible to the template size, shape, and functional groups arrangement. The MIPs have shown high selectivity and affinity for the target molecules with a substantial potential for the hormones detection as an environmental sensor. The objective of this research is to fabricate a label-free molecular imprinted polymer (MIPs) sensor and investigate the sensing ability for progesterone detection in aqueous solutions and blood. The Progesterone (PGN) is a cholesterol-long biosynthetic endocrine disruptor steroid and is naturally occurring estrogenic compound with a majority effect to alter the vital functions of the human body. The MIPs detection was based on the reflectance mechanism of inverse opal film, after the PG attachment into the photonic MIP binding sites modified the Bragg diffraction spectra of the films due to swelling and refractive index changes, producing the optical signal. MIPs were investigated by equilibrium binding, kinetics experiments, and UV- visible spectra that occurs with the rebinding at different progesterone concentrations in deionized water and 150 mM NaCl solutions. The MIPs response were investigated with progesterone concentration in the 1-100 [mu]g L-1 range; with LOD of 0.5 [mu]g L-1, reaching the detected range of hormone in natural waters. Furthermore, hydrogel MIP films were successfully tested in various real water matrices, they revealed satisfactory recognition ability towards the analyte, and a promising performance in challenging, unknown natural water samples. Moreover, the MIPs film exhibited good selectivity towards the progesterone hormone when exposed to structurally similar molecules, evidenced by a larger response than non-imprinted films (NIPs) due to the specific adsorption provided by molecular imprinting. Computational studies suggested that size along with surface potential influenced the binding of analog compounds. The molecularly imprinted polymer (MIP) were applied to whole blood and plasma samples of three different animals, the levels of free and total PG were analyzed along with different days of the estrous cycle of the cows. The commercial PG kits test results followed the same trend with MIPs test results for the non-bound PG in the blood samples. The measurements revealed the minimum concentration at day 0, and highest level between day 10 and 14. Both MIPs and commercial PG kits test results were in agreement in evaluating the PG levels trend during the estrous cycle, however, there was some variance in evaluating the exact concentrations of PG hormone during the cycle, but no discrepancy in determining the cow's pregnancy profile.Includes bibliographical references

MODELLING AND SIMULATION OF FIELD EMISSION IN CARBON NANOTUBE BASED IONIZATION GAS SENSOR

Gas sensors are of main interest in the field of oil and gas industry. They are used to sense corrosive gases in the pipelines and leakage in the delivery system. One of the recently developed gas sensor that has become the focal point of research is the ionization gas sensor. This sensor technology is still in its infancy and much can be done to increase the efficiency of the sensor. In this research, a new model to study the gas detection mechanism of carbon nanotube (CNT) based ionization gas sensor has been developed. The model incorporates electron field emission property of the CNTs. The new model consists of three modules, i.e., CNT particle injection module, CNT density and aspect ratio variation module, and CNT velocity assignment module. These three modules are combined together and embedded in the standard Particle-In-Cell / Monte Carlo Collision (PIC-MCC) codes. The integrity of the enhanced PIC-MCC codes has been validated by calculating the field enhancement factor, β. Furthermore, the functionality of these codes is checked by running simulations of DC discharges in different gases and comparing the results with published experimental and simulated works. With the help of enhanced PIC-MCC codes the simulation of gas breakdown behavior with CNT field emission effects become possible for the first time. From the results, around one order of magnitude decrease in the breakdown voltages is observed when CNT is used in ionization gas sensor. The electrostatic screening effects are reduced to a minimum when inter-tube spacing is equal to the height of the CNT. Faster response time is also observed with the presence of CNT in ionization gas sensor. These results suggest that by properly controlling the growth of CNT structures, an optimized CNT based ionization gas sensor can be realized