1. Introduction to Modeling  Define the terms  System  Surroundings  Input/output  Transducer  Distinguish between sensors and actuators  For a given transducer, identify the appropriate inputs and outputs  For a given transducer, find find/calculate  span,  full scale output,  sensitivity,  accuracy, and  resolution  Distinguish between static and dynamic response characteristics of transducers  For a given transducer, find find/calculate  response time,  overshoot,  gain, and  phaseshift, and  Explain the concept of resonance

2. Some definitions System : Region of space set aside for analysis Boundary : Defines a system such that everything within it is the system Surroundings : Everything outside the system Interactions between the system and surroundings: Inputs  from surroundings to the system Outputs  from system to the surroundings. boundary system surroundings “Stuff” can be a physical quantity (p. ej., masa, energía) or something more abstract (p. ej, information, a signal, or a reading)

3. Levels of modeling An automotive airbag system A block diagram

4. Levels of modeling

6. This is the “MEMS” you would buy.

7. Levels of modeling This is the “MEMS” you would buy. MEMS sensor This is the “MEMS” we usually model.

8. Levels of modeling MEMS sensor This is the “MEMS” we usually model. How many inputs/outputs are there? What are the inputs? What are the outputs? What is the relationship between the inputs and the outputs? What do we need to know about what is inside the “black box” in order to find those relationships?

9. Transducers Most MEMS are transducers. Sensors Input is some physical quantity whose value we wish to know (p. ej., temperatura) Output is some other physical quantity (p. ej., voltage) whose value correlates to the measurand Sensors measure something Actuators Input is usually a voltage or some other electrical signal Output is physical motion of some kind Actuators move something

10. Sensor or actuator? Thermometer Input Output Thermocouple Input Output

11. Sensor or actuator? Bimetallic micro-valve Input Output (http://www.konicaminolta.com) Ink jet print head Input Output

12. Sensor or actuator? Digital micromirror device Input Output Capacitive accelerometer Input Output

13. Sensor or actuator? Comb drive Input Output “Micro-reactor” microfluidic device Input Output

14. Loading The act of measuring alters the thing we’re trying to measure  loading

15. Power input to transducers Many sensors require a voltage supply as a second input to provide power for signal conditioning —circuits that help convert the output signal to a form useful for the application Sensors and actuators require different amounts of input power. Sensors are low input- power devices; actuators are high-input-power devices Power input Converted into the actuation output Control input Tells the system what to do

16. Transducer characteristics Static response characteristics Span (or full scale input) Range of input values over which a transducer produces output values with acceptable accuracy Units Same as input. (p. ej., Pa for a pressure sensor) Full-scale output (FSO) Range of output values corresponding to the span. Units Same as output (p. ej., V for a pressure sensor) For an actuator? μmμm

17. Transducer characteristics Static response characteristics Sensitivity Constant of proportionality between output and input for a linear transducer. Slope of the best-fit line. Units Output units/input units. Accuracy How close the transducer output is to (sensor) true value of the measurand, or (actuator) the desired output effect. Accuracy is determined by a calibration procedure

18. Transducer characteristics Static response characteristics Resolution (sensor) smallest detectable change in the measurand Units units of the measurand (actuator) smallest change in output that can effected by changing the input Units units of the output effect (e.g., μm for displacement)

19. Te toca a ti For the PX26-001DV model differential pressure transducer: 1.What is the measurand? 2.What is the span? 3.What is the full-scale output? 4.Determine the system sensitivity. 5.Can this transducer be used to measure Δ P, for P 1 = 25 psi and P 2 = 24.5 psi? Explain your answer.

20. Dynamic versus static response MEMS Transducer Steady inputSteady output Time varying input Time varying output Static response Dynamic response Step input Sinusoidal input Time

21. Response to step input MEMS Transducer Response time Time required for output to reach new steady state value Overshoot Amount the initial response exceeds the desired value Time or

22. Response to sinusoidal input MEMS Transducer Time y(t)y(t) Amplitude ratio (or gain ) Ratio of the output amplitude to the input amplitude Usually reported in decibels (dB) dB = 20log(gain). Can change as a function of the input frequency Can be magnified at some frequencies and attenuated (reduced) at others. Frequency Amplitude Phase  Same as frequency  larger, smaller, or the same  In or out phase

23. Response to sinusoidal input Resonance Large magnification at certain frequencies and not others Phase shift Amount of by which an output sine wave is “misaligned” with the input Usually reported as phase angle φ = ωt resonance frequencies in phaseout of phase

24. Response to sinusoidal input (not time) Shows both gain and phase Bode plot

25. Volunatarios para temas 1. Resistive sensing Piezoresistive sensing Magnetoresistive sensing Thermo-resistive sensing ______________________ 2. Capacitive sensing Piezoelectric sensing ______________________ 3. Resonant sensing Variable-frequency resonator Variable-amplitude resonator ______________________ 4. Thermoelectric sensing Thermo-electric cooling ______________________ 5. Magnetic sensing Reluctance sensing Inductive sensing ______________________ 6. Capacitive actuation Piezoelectric actuation ______________________ 7. Thermo-mechanical actuation Bimetallic actuation Thermopneumatic actuation Shape memory alloy actuation Hot arm actuation ______________________ 8. Magnetic actuation Magnetostrictive actuation ______________________