ECE5320 Mechatronics Assignment#01: Literature Survey on Sensors and Actuators Topic: Capacitive proximity sensorsOutlineReference listBasic Working PrincipleFunctionality ExampleSlide 6Slide 7Device DiagramTypes of Capacitive SensorsSlide 10Slide 11Slide 12Slide 13Slide 14Slide 15Selection ParametersRelative Merits of Capacitor SensorsMajor applicationsManufacturersECE5320 MechatronicsAssignment#01: Literature Survey on Sensors and Actuators Assignment#01: Literature Survey on Sensors and Actuators Topic: Capacitive proximity sensorsPrepared by: Sunil IndluruDept. of Electrical and Computer EngineeringUtah State [email protected]/9/200701/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-2Outline –Reference list–To probe further–Basic working principle–Functionality Example–Device Diagram–Types of Capacitor Sensors–Limitations–And many more relevant issues in applications (such as, how to choose, cost information, where to buy etc.)01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-3Reference list•http://ee.sharif.edu/~industrialcontrol/Summary_Automation_Sensors_tutorial.pdf•http://www.sensors-transducers.machinedesign.com/guiEdits/Content/bdeee4/bdeee4_7.aspx•http://www.howstuffworks.com•http://www.mech.utah.edu/~me7960/lectures/Topic6-SensorsAndEncoders.pdf01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-4Basic Working Principle •The sensing face of the sensor constitutes the armature of a capacitor.•A sine-wave voltage is applied to this face, creating an alternating electrical field in front of the sensor.•Since this sine-wave voltage is referenced in relation to a reference potential (ground or machine ground, for example), the second armature consists of an electrode connected to this reference potential (machine frame, for example).•These two electrodes facing each other form a capacitor of capacitance: where ε0 = 8.854 187 pF/m is the absolute permittivity of the vacuum and εr the relative permittivity of the material between the two electrodes01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-5Functionality Example•Case – 1 (No object between the 2 electrodes)01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-6Functionality Example•Case – 2 (Insulating object between the 2 electrodes)In this case the ground electrode can be the metal belt of a conveyor.For example: When the mean εr becomes greater than 1 in thepresence of an object, C increases.Measuring the increase in the value of C allowsthe presence of the insulating object to be detected.01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-7Functionality Example•Case – 3 (Conductive object between the 2 electrodes)The presence of a metal object thus leads to a rise in the value of C.01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-8Device Diagram01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-9Types of Capacitive Sensors• Capacitive sensors without a ground electrode These sensors use the principle described as in the previous slides. A path to ground (reference potential) is needed in order to detect an object. They are used for detecting conductive materials (metal, water) at considerable distances. Typical application: Detection of conductive materials through an insulating material.01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-10Types of Capacitive Sensors•Capacitive sensors with a ground electrode It is not always possible to find a path to ground, as would be the case if we wanted to detect the insulating container in the previous example. The solution, therefore, is to incorporate the ground electrode on the sensing face. This creates an electrical field, which is independent from a path to ground Typical application: Detection of all materials.Possibility of detecting insulating or conductive materials behind an insulating partition, e.g. cereals in a cardboard box.01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-1101/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-1201/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-1301/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-1401/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-1501/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-16Selection ParametersThe sensitivity of capacitive sensors according tothe basic equation depends on both the distance between the object and the sensor and the material from which the object is made i.e.,•Sensing Distance•Material (dielectric constant)01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-17Relative Merits of Capacitor Sensors Pros•Nearly universal sensing ; no need for special materials.•High speed. Use charging and discharging, therefore realizing full mechanical response speed. Cons•Force and distance inversely scaled - to obtain larger force, the distance must be small.•In some applications, vulnerable to particles as the spacing is small – needs packaging.•Vulnerable to sticking phenomenon due to molecular forces.•Occasionally, sacrificial release. Efficient and clean removal of sacrificial materials.01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-18Major applications •Industries:–Oil refineries, chemical & fertilizer plants–Hydroelectric, NG, coal, & nuclear power plants–Aircraft & naval engines–Heavy manufacturing equipment (Paper)Key Purposes–Bearing monitoring & diagnosis–Shaft/Rotor balancing & monitoring–Provide data for asset control & protection systems01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-19Manufacturers•Siemens Corp. •Honeywell Sensing & Control - Freeport, IL •Steiner Electric Co. •Spectec - Emigrant, MT •Turck, Inc. - Plymouth, MN •Festo Corp. - Hauppauge, NY •Many
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