1_sensors
TRANSCRIPT
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1.1. Definition
1.3. Classification of Sensors
1.4. Sensor Principles
1.5. Sensors Output Signals
1.6. Passive Sensors
1.7. Stages of Development of a Sensor System
1. Sensors
P. 1-1S. 1-1 Prof. Dr.-Ing. O. Kanoun
Chair for Measurement and Sensor Technology
1.2. Calibration of Sensors
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S. 1-2
1.1 What is a Sensor?
Sensor
[DIN 1319]
Sensor – Part of a measurement equipment that responds to a measurement quantity
Sensor - System, that converts a physical quantity and changes it in a suitable signal
Latin Sensus = The Sensing
Physical Quantity
or Event
Example: A resistance changes with temperatur
Also Sensing Element, Probe, Transducer
Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology
Excitation, Energy
Signal
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Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology
S. 1-3
A Sensor is a Transducer
Measurement Quantity
Environment Energy
Excitation
Energy Supply
Output Signal
Output Energy
mechanical
thermal
magnetic
Radiation
chemical
electrical
thermo electric effect
for temperature
measurement
Current or Voltage
el. resistance
S. 1-3
1.1 What is a Sensor?
P. 1-3
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Pressure
p el. Field E
Position
l
Resistance
R
Position
l
Capacitance
C
Rotation Speed el. Voltage
U
Temperature
T
Resistance
R
Temperature
T
el. Voltage
U
w
U
A B
Induktionsgesetz
R T R T ( ) ( ) 0 1
(Metalle)
U a T T m v ( )
Thermoelement
Non ElectricalSignal
Analog ElectricalSignal
Principle
Measurement Principle - physical principle in use
S. 1-4 Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology
1.1 What is a Sensor?
piezo electric effect
strain sensor
capacitive sensor
P. 1-4
induction
metals
thermo couple
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S. 1-5
Calibration-
To find out the relationship between Input and output quantity
[DIN 1319]
Prof. Dr.-Ing. O. KanounProfessur für Mess- und Sensortechnik
1.2 Calibration
Sensor
Real Value of the
Measurement Quantity Sensor Signal
M1 S1
M2 S2
M3 S3
Mi Si
Calibration Data
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S. 1-6
Possibilities of Calibration
Calibration by Comparisonusing a Precision Device Calibration by usingan Etalon
Etalon Sensor Sensor
Precision Device
S SE
Gn
Measurement
Quantity
Output Value
Real Value Real Value
Output Value
Prof. Dr.-Ing. O. KanounProfessur für Mess- und Sensortechnik
1.2 Calibration
M1 S1
M2 S2
M3 S3
Calibration Data
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S. 1-7
Calibration at a Fixed Point
(Water Triple Point) Calibration by Comparison
Example: Calibration of Thermometers
Prof. Dr.-Ing. O. KanounProfessur für Mess- und Sensortechnik
Vapor
ICE
Water
Thermostat Bath
1.2 Calibration
Tempered Liquid
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S. 1-8
Calibration Hierarchy
CompanyCalibration Certificate
Client
+ Data Scheet
Technical
Requirements
Product
ISO 90XX
Prof. Dr.-Ing. O. KanounProfessur für Mess- und Sensortechnik
1.2 Calibration
National
Etalon
Reference Etalon
Working Standard
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Information Technology
Aspects
- Signal
- System ability
- Signal parameters
Principle
- Resistive
- Capacitive
- Inductive
- Electrochemical
- …
Energy supply
- Active
- Passive
Development Level
- Elementary
- Integrated
- Intelligent
Application
- Automotive
- Environment
- Medicine
- Intelligent home
- Research and development
- …
1.2 Classification of Sensors
S. 1-9 Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology P. 1-9
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1.3 Measurement Principles
Example 1: Resistive Sensors
A
l R
l A
Changes of Geometry
Changes of the Resistivity
Measurement of strain, force, ..
Measurement of temperature, gas, ..
Principle: Resistance Changes
A
A
l
l
R
R
S. 1-10 Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology
: Specific resistance
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202010 1 T T aT T aR T R
C T R R 0at 00
131 109,3 K a
262 1058,0
K a
C T for
C T for K a
00
01018,4 3123
Example Platin-Resistance Thermometer
[IEC 751 / DIN EN 60751]
Class|T |= 0.39 K
-80°C – 120°C
Resistance Thermometer
1.3 Measurement Principles
S. 1-11 Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology P. 1-11
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Negative Temperature Coefficient Resistance
A better conductor if heated
Temperature Coefficient
T
b
T
b
T T b
ee Re R R 00 0
11
0
b: Material Constant
R0: Resistance at the Temperature T0
T Carier Density
012 T
bdT dR
R
NTC: Negative Temperature Coefficient
1.3 Measurement Principles
S. 1-12 Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology P. 1-12
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24d l R
d
l
: specific resistance
l
l Strain
l l
d d
Poisson Ratio
l
l
l l
d d
l l d
d
l
l
R
R
212
k
R
R 21 21k with
k R R 10
resistance:
S. 1-13 Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology
1.3 Measurement Principles
Strain Gauges
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Piezoresistive Effect
Strain Gauges (SG)
Higher Sensitivity
Small measurement Range
Metall SG Semiconductor SG
k R R 10 Dependence of the band structure of elasticlattice distortions due to the action ofexternal mechanical stresses.
Changes of
Geometry
Low Noise
Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology
1.3 Measurement Principles
P. 1-14
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Strain Gauges (SG) – Metall-SG
• Piezoresistive Effect in Metall-SG
• Dependence of the piezoresistive effect Material
Nominar Resistance value without load
Poisson- Number
LoadChanges of Geometry
Changes of theElectric
Resistance
Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology
1.3 Measurement Principles
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• Example: higher Bandgap of InSb at higher pressure
(also other Semiconductors - 1000 MPa)
• Piezoresistive Effect in Semiconductors
LoadDeformation of
the crystallattice
Change of themobility of
charge career
Changes of resistivity
• Dependence of the piezoresistive Effect Orientation of the semiconductor cristall
Doping of the semiconductor
Type
Density
Distribution
Strain Gauges (SG) – Semiconductor-SG
Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology
1.3 Measurement Principles
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• Metall-SG
Wire-SG Wound Wire (d ≈ 20 µm)
Application by adhesive
Foil-SG
h ≈ 10 µm
Application by adhesive
Thin Film-SG
Application by sputtering or direct vapor deposition under
vakuum conditions (0,1 µm < h < 5 µm)
• Semiconductor-SG p- oder n-doped silicon (h ≈ 15 µm)
Application by adhesive or sputtering
Strain Gauges (SG) – Realization
Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology
1.3 Measurement Principles
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Strain Gauges (SG) – Examples
Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology
1.3 Measurement Principles
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nichtlineares Verhalten
Werkstoff Zusammensetzung k-Faktor
Konstantan 58% Cu, 42% Ni 2,04 bis
2,12
Nichrome V 80% Ni, 20% Cr 2,1 bis
2,63Nickel x% Ni -12 bis
20
Platin x% Pt 4,1
p-Si [111] 175
n-Si [100] -133
Strain Gauges (SG) – Materials
Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology
1.3 Measurement Principles
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Pressure Measurement Cell, Force Measurement
Sensors with Semiconductor strain gauges:
S. 1-20 Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology
1.3 Measurement Principles
Strain Gauges
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Photo Resistance
S. 1-21 Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology
Further Resistive Sensors
1.3 Measurement Principles
Anisotrope Magneto Resistive Effect (AMR)
Giant Magneto Resistive Effect (GMR)
Ni/Fe/Co
Ni/Fe/Co
Cu 5-10nmII
Without field
Higher Resistance
With magnetic field
Lower Resistance
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Resistive Sensors are mainly based on changes of resistvity or geometry
Are used for different Measurement quantites like:
- Temperature- Strain ( forces, pressure)
- Light
- Magnetic fields, position
Challenges are for example:
- Sensitivity- Measurement range
- Sensitive measurement procedures for small changes around a realitve
big nominal value
- Linearity should be investigated
- Wires may have an impact on the measurement value (small resistances,
temperature gradients along the wires)
- Contact resistances
What did we learn?
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Capacitive Sensors
Principle: Capacitance Changes
d
AC
r
0
Distance Changes
Changes of the Dielectric
Surface Changes
Changes in the Stray Field
Distance, Position, Material Thickness
e. g. Pressure Measurement
Distance, Position
e. g. Measurement of a Shift
Fill level, Humidity, Thickness of a Layer
e. g. Detection of Snow at an Airplane Wings
Detection of Conducting Material
e. g. Protection of Paintings in Museum
d
A
r
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1.3 Measurement Principles
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S. 1-24 Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology
1.3 Measurement Principles
Capacitance with Changes in Distance Capacitance with Changes
in Surface
Capacitance with Layered Dielectric
and Changes of Dip in DepthCapacitve Fill Level Sensor
for Isolating Liquids
P. 1-24
1 3 M t P i i l
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Capacitive Pressure Sensor:
Pressure
Application: Microphones
S. 1-25 Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology
1.3 Measurement Principles
P. 1-25
1 3 M t P i i l
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Capacitive Sensors
S. 1-26 Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology
1.3 Measurement Principles
P. 1-26
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Capacitive sensors are able to measure changes of position, geometry and
material properties of the dielectric material
Examples for measurement quantities are:- Position
- Material thickness
- Moisture
- Fill level
- Pressure
For calculation of the haracteristic of the sensor, generally we should think about
parallel and series connection of part-capacitances.
Dependence on surface is linear, on distance is hyperbolic ( suitalbe only for
small distances)
Challenges:
- Stray field
- Unwanted changes of the geometry
- Sensitivity to conducting materials in the stray field, …
- Films can be built on the electrodes (Fill level Sensor)
- Moisture dependence
What did we learn?
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2
0
2
N A
µµR
N L r
m
Electro dynamic Measurement principles:
Magneto-elastic principle
N: Number of Windings
Rm: Magnetic Resistance
µ: Permeability
l , A: Length and cross section of the iron core
L: Inductance
Eddy current sensor
µAR m
Inductive Sensors
S. 1-28 Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology
1.3 Measurement Principles
P. 1-28
Inductive Sensors1 3 Measurement Principles
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Elektrodynamische FühlerElectro dynamic principles
S. 1-29 Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology
Inductive Sensors1.3 Measurement Principles
P. 1-29
Inductive Sensors1 3 Measurement Principles
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S. 1-30 Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology
Inductive Sensors1.3 Measurement Principles
Eddy current principle
P. 1-30
Magnetic field of the inductance
Eddy currents in the target material
Eddy currents in the target material
Opposite magnetic field
Damping of the inductance
Measurements of:
- Material properties
- Material failures
- Distance (Proximity Sensor)
1 6 Classification of Sensors
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Information Technology
Aspects
- Signal
- System ability
- Signal parameters
Principle
- Resistive
- Capacitive
- Inductive
- Electro chemical
- …
Energy supply
- Active
- Passive
Development Level
- Elementary
- Integrated
- Intelligent
Application
- Automotive
- Environment
- Medicine
- Intelligent Home
- Research and Development
- …
1.6 Classification of Sensors
S. 1-31 Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology P. 1-31
1 4 S O t t Si l
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System ability Bus comunication
Output signalAnalogsignal
Binarysignal
Without buscommunication
Digitalsignal
Overfill sensorTemperatureExample:
Examples: CAN, LON, ASI, ..
S. 1-32 Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology
1.4. Sensor Output Signals
P. 1-32
1 4 Sensor Output Signals
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Amplitudeanalog
Frequencyanalog
digital
Value
t
Timeanalog
Value
t
Value
t
Value
t
Signal value ~ Measurand Time ~ Measurand Frequency ~ Measurand Digital value ~ Measurand
t1 t2
f 2f 1
Static accuracy
Dynamic
Sensitivity to distortion
Signal processing
Static accuracyDynamicSensitivity to distortionSignal processing
S. 1-33 Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology
1.4. Sensor Output Signals
P. 1-33
1 6 Classification of Sensors
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Information Technology
Aspects
- Signal
- System ability
- Signal parameters
Principle
- Resistive
- Capacitive
- Inductive
- Electro chemical
- …
Energy supply
- Active
- Passive
Development Level
- Elementary
- Integrated
- Intelligent
Application
- Automotive
- Environment
- Medicine
- Intelligent Home
- Research and Development
- …
1.6 Classification of Sensors
S. 1-34 Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology P. 1-34
1 5 P i S
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Passive Sensors
IDT
ReflectorsAntenna
RF request signal
RF response
Piezoelectric
crystal
Requestunit
Surface Acustic Wave -Sensors
Active Sensors
Piezo Electric Sensors
SensorEnergy Supply
Amplitude, Frequenz
Phase, Ankunftszeit
S. 1-35 Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology
1.5. Passive Sensors
P. 1-35
1 5 Passive Sensors
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36
v T T K U
Seebeck effect
F 2
E F1 E F2
F 1
Metal 1 Metal 2
Vakuum-Niveau
E F
F 1
E F
F 2
Metal 1 Metal 2
Kontaktspannung U
Metal 2
UT
Measurement
Point
TV
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-200°C to +1000 °C
|T |= 0.25% -0,75 % of the measurement range limits
Example: Typ K (NiCr-Ni)
100K
mV 4,1)
100K
mV(-1,9 –
100K
mV 2,2K
Thermo electric voltage
should be amplified!
Examples for thermo couples
S. 1-37 Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology
1.5. Passive Sensors
P. 1-37
1 5 Passive Sensors
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Piezo electric effect
Quarz Cristal
+
+
+
-
-
-Si
O
YF
YF
++++++++
+++
--------
---
-
-
-
+
+
+Si
O
x
yz
S. 1-38 Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology
1.5. Passive Sensors
P. 1-38
1 5 Passive Sensors
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Piezo electric sensors
Acceleration sensors
S. 1-39Prof. Dr.-Ing. O. Kanoun
Chair for Measurement and Sensor Technology
Prof. Dr.-Ing. O. Kanoun
Chair for Measurement and Sensor Technology
1.5. Passive Sensors
P. 1-39
1 6 Classification of Sensors
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Information Technology
Aspects
- Signal
- System ability
- Signal parameters
Principle
- Resistive
- Capacitive
- Inductive
- Electro chemical
- …
Energy supply
- Active
- Passive
Development Level
- Elementary
- Integrated
- Intelligent
Application
- Automotive
- Environment
- Medicine
- Intelligent Home
- Research and Development
- …
1.6 Classification of Sensors
S. 1-40Prof. Dr.-Ing. O. Kanoun
Chair for Measurement and Sensor Technology P. 1-40
1 6 Stages of Development of a Sensor System
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Signal
Measurement
Signal
Preprocessing
Signal
Processing
Elementar Sensor
Integrated Sensor
Intelligent Sensor
Prof. Dr.-Ing. O. Kanoun
1.6. Stages of Development of a Sensor System