Transcript Inputs - Rose

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
Some definitions
System:
Region of space set aside for analysis
boundary
Boundary:
Defines a system such that everything within it is
the system
Surroundings:
Everything outside the system
system
Interactions between the system and surroundings:
• Inputs  from surroundings to the system
• Outputs from system to the surroundings.
“Stuff” can be a physical quantity (p. ej., masa,
energía) or something more abstract (p. ej,
information, a signal, or a reading)
surroundings
Levels of modeling
A block diagram
An automotive airbag system
Levels of modeling
Levels of modeling
Levels of modeling
This is the “MEMS” you
would buy.
Levels of modeling
This is the “MEMS” you
would buy.
MEMS
sensor
This is the “MEMS” we
usually model.
Levels of modeling
• What is the relationship between the
• How many inputs/outputs are there?
inputs and the outputs?
• What are the inputs?
• What do we need to know about what
• What are the outputs?
is inside the “black box” in order to find
those relationships?
MEMS
sensor
This is the “MEMS” we
usually model.
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
Sensor or actuator?
Thermometer
Input
Output
Thermocouple
Input
Output
Sensor or actuator?
Bimetallic micro-valve
Input
Output
Ink jet print head
Input
(http://www.konicaminolta.com)
Output
Sensor or actuator?
Digital micromirror device
Input
Output
Capacitive accelerometer
Input
Output
Sensor or actuator?
Comb drive
Input
Output
“Micro-reactor” microfluidic device
Input
Output
Loading
The act of measuring
alters the thing we’re
trying to measure
 loading
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
Power input
Converted into the actuation output
Control input
Tells the system what to do
Sensors and actuators require different amounts of input power. Sensors are low inputpower devices; actuators are high-input-power devices
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?
μm
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
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)
Te toca a ti
For the PX26-001DV model differential pressure transducer:
1.
2.
3.
4.
5.
What is the measurand?
What is the span?
What is the full-scale output?
Determine the system sensitivity.
Can this transducer be used to measure ΔP, for P1 = 25 psi and P2 = 24.5 psi? Explain your
answer.
Dynamic versus static response
Steady input
Time varying
input
MEMS
Transducer
Steady output
Static response
Time varying
output
Dynamic response
Sinusoidal input
Step input
Time
Time
Response to step input
MEMS
Transducer
Time
Time
Response time
Time required for output to reach
new steady state value
Overshoot
Amount the initial response exceeds
the desired value
or
Response to sinusoidal input
y(t)
Time
MEMS
Transducer
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.
Time
Frequency  Same as frequency
Amplitude  larger, smaller, or the same
Phase
 In or out phase
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 phase
out of phase
Response to sinusoidal input
Shows both gain and phase
Bode plot
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
______________________