Search for: capacitive-sensors
M.Sc. Thesis Sharif University of Technology ; Golnabi, Hossein ; Gobal, Fereydoon
Estimation of physical parameters for solutions and mixed liqids are used widely in industrial applications. However, we can do these measurements with conventional laboratory analysis, but we always want to find an easy and quick method that use on-line measurements. In this study electrical properties of different water liquids and mixture samples in frequency stepwise range of 100-100000 Hz are measured by using a short cylindrical capacitive sensor and a measuring module (LCR-703).Operation of the capacitance measurement module for such probes is based on the auto-balancing bridge method.The effects of frequency and volume fraction on the electrical parameters and permittivity of mixed...
Investigation of water electrical parameters as a function of measurement frequency using cylindrical capacitive sensors, Article Measurement: Journal of the International Measurement Confederation ; Volume 46, Issue 1 , 2013 , Pages 305-314 ; 02632241 (ISSN) ; Sharifian, M ; Sharif University of Technology
In this study electrical properties of different water liquids at frequency range of 100-2000 Hz are investigated by using the short invasive and non-invasive cylindrical capacitive sensors (CCSs). Operation of the capacitance measurement module for such probes is based on the auto balancing bridge method. Comparison of the measured capacitances and measured resistances for different water liquids shows decrease by increasing the frequency. In another study the dielectric constant of distilled water, mineral water, tap water and salt water are measured. The effects of the frequency on the resistivity, permittivity and conductance of the different water liquids are also investigated
M.Sc. Thesis Sharif University of Technology ; Karbalaee Aghajan, Hamid
To create applications for smart environments we can select from a huge variety of sensors that measure environmental parameters within the premises. Capacitive proximity sensors use weak electric fields to recognize conductive objects, such as the human body. They can be unobtrusively applied or even provide information when hidden from view which make these sensor more popular. Furthermore, these sensors are low cost, precise and low power. In this thesis, we study the construction and operation of capacitive sensors and the challenges of using them. Then we use them to produce smart devices. Smart flooring is used on the ground and it can be used to track people or fall detection. Smart...
Investigation of Water Electrical Parameters as a Function of Measurement Frequency and Concentration Using Cylindrical Capacitive Sensors, M.Sc. Thesis Sharif University of Technology ; Golnabi, Hossein ; Gobal, Fereydoon
The electrical conductivity of the solution has been one of the important physical quantities in many application. In this respect many probes and devices such as conductive sensors have been devised. In this study electrical properties of different water samples at frequency step range of 100-100000 Hz are measured by using the long cylindrical capacitive sensor and a measuring module (LCR-703). Operation of the capacitance measurement module for such probes is based on the auto balancing bridge method. Comparison of the measured capacitances and measured resistances for different water samples shows a decrease by increasing the measurement frequency. In another study the dielectric...
M.Sc. Thesis Sharif University of Technology ; Ghanbarpour Asl, Habib
This paper presents a novel method for satellite attitude determination, using Electrostatically Suspended gyroscope (ESG). In this method, two superconducting rings rotated around a spherical rotor, which causes a variable flux in rings. So according to faraday’s law of induction, a voltage will be induced in the rings. Using this voltage and a kalman filter, attitude of satellite will be determined. ESG works precisely, when the rotor is maintain at the center of gyroscope cavity, between three pairs of circular electrode, so a backstepping control algorithm will be designed In order to this purpose. The performance of attitude determination using this ESG and designed control algorithm is...
Article Journal of Applied Sciences ; Volume 9, Issue 8 , 2009 , Pages 1556-1561 ; 18125654 (ISSN) ; Golnabi, H ; Sharif University of Technology
In this study a more precise formulation of electrical capacitance for a cylindrical capacitive sensor is reported. By using different theoretical models such as Coulomb law, Gauss law and Laplace equation the electrical capacitance is calculated. Based on the given models the relation between the capacitance and the geometrical parameters (e.g., cylindrical length) is formulated and by using suitable software capacitance variation is computed and compared for different methods. In Coulomb method, the electrical potential is first solved numerically by using Mathematica and then the electrical capacitance is computed. It is found that the active capacitor length is crucial parameter in the...
Article Journal of Applied Sciences ; Volume 8, Issue 9 , 2008 , Pages 1699-1705 ; 18125654 (ISSN) ; Azimi, P ; Sharif University of Technology
In this study, design and operation of a cylindrical capacitive sensor based on the dielectric and reactance capacitance changes of the gap medium is reported. The proposed system was used to determine the electrical properties of different water liquids as a result of the capacitance variations. For capacitance measurement, the cylindrical gap can be filled up by water liquids under study, the electrical characteristics of different water liquids, mixture of ethanol and water, mixture of methanol and water, mixture of petroleum and water and other liquid mixtures were studied. In this research a big difference about 16200 nF was noticed in the measured capacitance of the corresponding...
Article Mechanics and Industry ; Vol. 15, issue. 2 , January , 2014 , p. 139-145 ; Ghafari, A. S ; Sharif University of Technology
This paper presents closed loop simulation of a CMOS-MEMS force sensor for biomedical applications employing an optimal proportional-integral-derivative controller. Since the dynamic behavior of the sensor under investigation is nonlinear the iterative feedback tuning approach was proposed for optimal gains tuning of the proposed controller. Simulation results presented in this research illustrate that the proposed controller suppresses the undesired in-plane vibration induced by environment or gripper 40 times faster than the nonlinear controller proposed in the literature. To suppress the maximum input disturbance the maximum voltage was approximately 18 V which was less than the pull-in...
Design of electrostatic actuators for suppressing vertical disturbances of CMOS-MEMS capacitive force sensors in bio applications, Article Mechanics and Industry ; Volume 16, Issue 3 , 2015 ; 22577777 (ISSN) ; Selk Ghafari, A ; Khayyat, A. A ; Sharif University of Technology
EDP Sciences 2015
The objective of this work is to design electrostatic actuators for a CMOS-MEMS nano-newton capacitive force sensor to suppress vertical vibrations disturbances. Electrostatic actuators are selected because the movable part of this force sensor is anchored to the fixed parts. In the first step, we propose a framework for simulation of the force sensor based on finite element method. The proposed model is modified utilizing comparison between the simulation and experimental models to improve the performance of the model. Then, 14 pairs of electrostatic actuators are designed for applying the control algorithm and their pull-in voltage is calculated. In next step, Modal Analysis is applied to...
Investigation of conductivity effects on capacitance measurements of water liquids using a cylindrical capacitive sensor, Article Journal of Applied Sciences ; Volume 10, Issue 4 , 2010 , Pages 261-268 ; 18125654 (ISSN) ; Golnabi, H ; Sharif University of Technology
In this study by using a Cylindrical Capacitive Sensor (CCS), the Electrical Conductivity (EC), effects on the capacitance measurements of the water liquids was investigated. Theoretical values of the capacitance measurements of water liquids with the cylindrical length in the range 0.5-5 cm are calculated. Our obtained results indicate that measured capacitance value by CCS depends on the liquid capacitance and reactance capacitance. Liquid capacitance value of the distilled water for permittivity of 80 is about 33.5 pF and reactance capacitance value is about 0.290 μF, when the cylindrical length value is about 1.6 cm. The reactance capacitance for the mineral, tap and dilute salt water...
Active vibration control of a cmos-mems nano-newton capacitive force sensor for bio application using PZT, Article Advanced Materials Research, San Diego, CA ; Volume 628 , 2013 , Pages 317-323 ; 10226680 (ISSN) ; 9783037855706 (ISBN) ; Selkghafari, A ; Zabiholah, A ; Meghdari, A ; Sharif University of Technology
This paper reports the design of an optimal controller to prevent suppressvertical vibration due to undesired out of plane excitations generated by environment or gripper during manipulation for a CMOS-MEMS Nano-Newton capacitive force sensor applied for biomedical applications. Undesired out of plane excitations generated by environment or gripper during manipulation is the most prevalent source of vertical vibration in this type of sensors. To suppress the vibrational movement a PZT 5A is used as actuation mechanism. Discrete element method DEM model and Modal analysis were used to find dominant natural frequencies and mode shape vectors. To eliminate out of plane excitation an optimal...
Comparison of invasive and non-invasive cylindrical capacitive sensors for electrical measurements of different water solutions and mixtures, Article Sensors and Actuators, A: Physical ; Volume 167, Issue 2 , June , 2011 , Pages 359-366 ; 09244247 (ISSN) ; Golnabi, H ; Sharif University of Technology
In this study design and operation of invasive and non-invasive cylindrical capacitive sensor (CCS) designs for the electrical measurements of water, water solutions, and water mixtures are reported. Operation of the capacitance measurement module for such probes is based on the charge/discharge method. The measured capacitances and resistances for distilled water, mineral water, tap water and salt water samples are reported by using two sensor types and results are compared. The measured capacitance by invasive CCS for distilled water is about 2.28 μF and by non-invasive CCS is 31.40 pF, which shows a big difference for different probes. Such a difference is due to the electrical...