1. ECE699 – 004 Sensor Device Technology
Chapter 5 Velocity and Acceleration, Force, Strain and Pressure
Fall 2018
George Mason University

2. 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

3. Linear velocity sensors is limited by the size of the sensors

4. 2. Capacitive Accelerometers
Displacement  change in capacitance
d1 and d2 change b/c mass movement

6. Different designs

7. 3. Piezoresistive Accelerometers
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

8. 4. Piezoelectric Accelerometer
Sense vibration and acceleration
Wide operation temperature (up to 120oC)
Frequency: 2 Hz – 5 kHz
Mostly based on PZT material

9. 5. Thermal Accelerometers 5.1 Heated-Plate Accelerometer

10. 5.2 Heated-gas accelerometers

11. 6. Gyroscopes The most common navigation sensor Especially when the geomagnetic field is not avialable The keeper of direction - because of the principle of the conservation of angular momentum.

12. 6.1 Rotor Gyroscope

13. 6.2 Monolithic Silicon Gyroscope -It can be scaled down in comparison to rotor gyro

14. 6.3 Optical Gyroscope

16. 7. Piezoelectric cables - Use for vibration detection, forces measurement in highway