ECE5320 Mechatronics Assignment#01: Literature Survey on Sensors and Actuators Topic: Differential-Capacitance AccelerometerOutlineReference listTo explore further (survival pointers of web references etc)Major ApplicationsMajor Applications (continued.)Basic working principleSlide 8Slide 9Slide 10Slide 11Slide 12Slide 13A Sample configuration of accelerometerA Typical ApplicationMajor SpecificationsSlide 17LimitationsSlide 19ECE5320 MechatronicsAssignment#01: Literature Survey on Sensors and Actuators Assignment#01: Literature Survey on Sensors and Actuators Topic: Differential-Capacitance AccelerometerPrepared by:Vikranth CeakalaDept. of Electrical and Computer Engineering Utah State University3/9/200701/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-2Outline –Reference list–To probe further–Sensor – Differential-Capacitance Accelerometer•Major applications•Basic working principle illustrated•A sample configuration of an accelerometer•A typical application•Major specifications•Limitations01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-3Reference list1. Bishop, Robert H; The Mechatronics Handbook, CRC Press 20022. Senturia, Stephen D; Microsystem Design3. http://www.ee.ucla.edu/~wu/ee250b/4. http://www.analog.com/01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-4To explore further (survival pointers of web references etc) http://www.sensorland.com/http://www.howstuffworks.com/01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-5Major Applications •Measurement of Acceleration, Velocity and Position•Monitor the health of machinery by keeping track of the vibrations.•Measure the position of an object in space. - by making use of 3 accelerometers, to measure each of the x, y and z axes.01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-6Major Applications(continued.) •Computer input devices - Mouse. - Joysticks.•Crash detection devices in automobiles.01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-7Basic working principle•Change of Capacitance due to acceleration of an object.•Acceleration changes the width of dielectric material between capacitor plates.•The change in width causes the change in capacitance.01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-8Basic working principleDiagram showing the principle of a differential capacitance system01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-9Basic working principle A differential capacitance accelerometer in steady state.01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-10Basic working principle A differential capacitance accelerometer in action.01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-11Basic working principle•Change in Capacitance due to motion.–C1 and C2 are equal when the accelerometer is steady.–C1 and C2 change when the object moves, thus changing V0 as a function of displacement.The relation between output Voltage V0 and the displacement dx is given as.01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-12Basic working principle•Change in output frequency due to motion. Capacitance can be expressed as k is the dielectric constant, ε is the permittivity of free space, S is the area of the electrode, and h is the variable gap.The variable gap h is a function of acceleration “a”, mass “m” and spring constant “k”. Hence we have a variable capacitance.01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-13Basic working principleSince Capacitance C is inversely proportional to the acceleration and Frequency is inversely proportional to capacitance.The output frequency is directly proportional to the acceleration. which is given by Where f0 is the frequency at zero acceleration, and fa is the frequency due to the change in acceleration.01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-14A Sample configuration of accelerometer01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-15A Typical ApplicationSensing change in inertia in airbag crash detection systems in automobiles.By the analysis of acceleration, velocity and position one can detect a crash. In the above figure the irregular spikes represent a crash.01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-16Major Specifications•Two basic design configurations–Compression type•Crystal is held in by compression•Vibration varies the stress–Shear-stress type•Vibration deforms the crystal•Transducer–Outside power source is not needed, provides all the power it needs01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-17Major SpecificationsProof mass of 0.1ugrams.Minimum detectable beam length 0.2 angstrom.Resonant frequency of the beam 10 to 22 kHz.Smallest detectable change in capacitance 20 amtoF.01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-18Limitations•External power supply needed.•Additional circuitry needed for signal conditioning of the sensor output. - amplifier, ocillator and low pass filter01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-19Thank YouVikranth
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