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MSU ECE 480 - Technical_presentation

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ECE 480 – Team 6Slide 2Background (cont...)Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Touch sensorTouch sensor (cont...)Slide 12Vehicle Identification Capacitive SensorCapacitive sensor structureSlide 15Slide 16Capacitive Sensors for Thickness MeasurementCapacitive Sensors for Thickness MeasurementSlide 19Slide 20ConclusionECE 480 – Team 6In Order of Presentation:Ishaan SandhuDanny KangAnuar TazabekovArslan QaiserEric OtteHow to Choose/Use Capacitive Sensors for Various ApplicationsBackground• Three Main Types:• Displacement• Touch Sensor and iPod Click Wheel• Accelerometer• Automobile Suspension System, Air Bag System, ABS• Pressure• Tire PressureBackground (cont...)•Capacitance •Electric Fringe Fields•Dielectric differencesBackground (cont...)•Advantages of Capacitive Sensor•Higher accuracy•Smaller size•More reliable (compared to mechanical)•No moving parts (more durable)•No direct contact with the sensor•Sealed from dirt•CheaperWater level sensor•Metal electrode•Ground vessel•Dielectric change causes change in capacitanceWater Level Sensor (cont...)•Figure shows simplified view•Typical Applications:•Gas Tank Sensor•Water Reservoir•Production Vats•Cheaper than similar sensors•More AccurateAirbag System•Required by Government law since 1999 model year•Capacitive Pressure Sensor and Capacitive Accelerometer Sensor are used for passenger protection•Sense a passenger.•Capacitive Pressure Sensor•Use a thin diaphragm•Pressure is detected based on change in the capacitance between the diaphragm and the electrodeAirbag System•Sense a crash•Capacitive Accelerometer Sensor•A change in electrical capacitance with respect to accelerationAirbag SystemTouch sensor•Electrical disturbance•Two plate sensor•Surface charge•Overlay of 1-3mmTouch sensor (cont...)•Interaction with E-fields•E-fields projects through material•Responsive to conductive devicesTouch sensor (cont...)•Change in capacitance •Dielectric permittivity influence•Common applications–Touch screens (ex. iPhone, Nexus1)–Track padsVehicle Identification Capacitive Sensor• Used at road toll stations • Current Inductive sensors • Drawbacks:• Covers large area• Senses only metal• Not very accurate• Solution: Use a capacitive sensorCapacitive sensor structure• 11 Excitation and 30 detection electrodes• B0 (detection circuit and CtD)• B0 connects to B1-B30• Capacitance between plates A and B• Sensor embedded into a ramp• Help slow the cars down• Stray capacitanceStructure (cont...)• Cx is very small • Cs1 and Cs2 are large • Measured Cx: V3 = 2fVcCxRf + V1-V2• Detection of 0.001 pF• Sensitivity 1V/pFCapacitance measuring circuitCapacitive Sensors for Thickness Measurement Utilizes high-performance, complex sensorsResolution down to less than one nanometerThickness measurement: capacitive vs. inductiveEx: Measuring the thickness of silicon wafersCapacitive Sensors for Thickness Measurement•Components:•Probe: Device which emits the electric field•Probe Guard: Shapes the electric field•Circuitry: Measures very small changes in capacitance using complex algorithmsCapacitive Sensors for Thickness Measurement•Single channel:•Only one sensor probe•Non-flat surfaces produce error•Dual channel:•Uses two sensors placed on opposite sides of object to be measured•Nulls out curved surface errors due to differential operationCapacitive Sensors for Thickness Measurement•Typical Applications?•Machining•Manufacturing•Precision thickness measurementsConclusion•Background•Water Level•Air Bag deployment systems•Touch sensors•Vehicle detection system•Thickness


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MSU ECE 480 - Technical_presentation

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