1. Instrumentation (AMME2700) 1 Instrumentation Dr. Xiaofeng Wu

2. Instrumentation (AMME2700) Piezoelectric Sensors  A piezoelectric material produces an electric charge when it is subjected to a force or pressure.

3. Instrumentation (AMME2700) Voltage Follower Circuit for Piezoelectric Sensors 3

4. Instrumentation (AMME2700) Displacement, Velocity and Acceleration Measurement in Inertial Space

5. Instrumentation (AMME2700) Dynamic Response of the Seismic Model

6. Instrumentation (AMME2700) Seismic Acceleration Transducers: Linear Seismic Accelerometer

7. Instrumentation (AMME2700) Accelerometer Design

8. Instrumentation (AMME2700) Piezoelectric Accelerometer Characteristics

9. Instrumentation (AMME2700) Example 1 9 An accelerometer with a charge sensitivity of 100pC/g ±1pC/g (95%) and a capacitance of 200pF ± 2pF (95%) is connected to a voltage follower with an input connector capacitance of 20pF (in parallel with the cable capacitance), a 10,000pF blocking capacitor and a 100MΩ resistance. A 3m long cable with a capacitance of 280pF connects the accelerometer and the voltage follower. Determine: 1.The schematic of the instrument; 2.The instrument’s sensitivity in mv/g;

10. Instrumentation (AMME2700) Temperature Measurement

11. Instrumentation (AMME2700) Expansion Methods for Measuring Temperature 1.Liquid-in-Glass Thermometer 1) An operator is needed, so the thermometer cannot be used in a closed- loop control systems. 2)The time required to reach the equilibrium temperature is excessive 2.Bimetallic Thermometer The bimetallic sensor is used in temperature control systems, and is the primary element in most dial thermometers and many thermostats.

12. Instrumentation (AMME2700) Resistance Thermometers  Resistance temperature detector (RTD)  Materials like platinum, nickel and so on  Stable and provide a reproducible response to temperature over long periods of time  Thermistors  Fabricated from semiconducting materials  Very high accuracy

13. Instrumentation (AMME2700) Resistance Temperature Detector  A RTD consists of a wire coil sensor, a sheath, a linearizing circuit, a Wheatstone bridge, and a voltage display instrument.

14. Instrumentation (AMME2700) Resistance Temperature Detector γ 1, ··· γ n are temperature coefficients of resistivity R 0 is the resistance of the sensor at a reference temperature T 0.

15. Instrumentation (AMME2700) Sensor Circuit

16. Instrumentation (AMME2700) Example 2  An RTD forms one arm of an equal-arm Wheatstone bridge. The fixed resistances, R 2 and R 3 are equal to 25Ω±0.01 Ω (95%). The RTD has a resistance of 25Ω at a temperature of 0 o C and is used to measure a temperature that is steady in time. Suppose the coefficient of resistance for this RTD is 0.004 o C -1. A temperature measurement is made by placing the RTD in the measuring environment and balancing the bridge by adjusting R 1. The value of R1 required to balance the bridge is 37.36Ω. Determine the temperature of the RTD and its uncertainty.