ECE699 004 Sensor Device Technology Chapter 5 Velocity and Acceleration Force Strain and Pressure Fall 2018 George Mason University 1 1 Velocity and Acceleration Currently speed of large objects can be well determined by GPS time delay of signals from a number of Earths satellites ID: 763995
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ECE699 – 004Sensor Device Technology Chapter 5 Velocity and Acceleration, Force, Strain and PressureFall 2018George Mason University 1
1. Velocity and Acceleration Currently, speed of large objects can be well determined by GPS: time delay of signals from a number of Earth’s satellites It is difficult to detect the speed of small objects 2
Linear velocity sensors is limited by the size of the sensors 3
2. Capacitive Accelerometers Displacement change in capacitance d1 and d2 change b/c mass movement 4
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Different designs 6
3. Piezoresistive Accelerometers 7 The mass feels the force, adding a strain on the gauge Advantage: withstand overshock upto 10,000g Disadvantages: it is made of discrete, epoxy-bonded strain gauges – not good for temperature variation
4. Piezoelectric Accelerometer Sense vibration and accelerationWide operation temperature (up to 120oC)Frequency: 2 Hz – 5 kHzMostly based on PZT material 8
5. Thermal Accelerometers 5.1 Heated-Plate Accelerometer9
5.2 Heated-gas accelerometers 10
6. Gyroscopes The most common navigation sensorEspecially when the geomagnetic field is not avialableThe keeper of direction - because of the principle of the conservation of angular momentum. 11
6.1 Rotor Gyroscope 12
6.2 Monolithic Silicon Gyroscope -It can be scaled down in comparison to rotor gyro13
6.3 Optical Gyroscope 14
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7. Piezoelectric cables - Use for vibration detection, forces measurement in highway16
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