Introduction to Sensors

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Introduction to Sensors

• Sensors Technology
• AUE 2008
• Bo Rohde Pedersen

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Sensors Focusing Installations

• General measuring terminologies
• Measuring basic level information
• Temperature
• Light intensity
• Force
• Advanced sensors
• Movement
• Distance
• Accelerometer

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Sensitivity
Sensitivity How big change gives a change in the
measured signal (S) on the output of the
sensor Example When a 1V signal is forced to a
old-fashioned voltmeter or VU-meter what will
it show.
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Accuracy
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Precision
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Temperature NTC and PTC
Negative Temperature Coefficient Is a resistor
with a large negative temperature
coefficient Positive Temperature
Coefficient Is a resistor with a large negative
temperature coefficient Made of Carbon,
Iron, Silicon. Linearity Nonlinear function
between resistance and temperature
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Temperature Integrated Sensor
Inside of an intergraded device
The aim is to make a linier devise which in our
case is easy to use. In this case is the
temperature measurement device based on Silicon.
Remember to check manufactory specification for
setup and use
Example National LM34
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Temperature Other

• Hall element/ thermocouples Concept like a
  battery
• Bimetal Often on/off. Typical used for
  regulating irons, ovens etc.

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Strain Gages
Piezoresistive Element Resistance change takes
place when length or area are changed. Made
of Wire, metal foil or semiconductor. Linearity
Nearly linear function between resistance and
force
Sensitivity
One direction
Two direction
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Force Sensor

• Changes resistance
• Ranges from 100M Ohms at 0 kg, to 15 Ohms at 3kg
  

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Flex Sensors/Bend Sensor
Flex Sensor Is a resistor that changes the
ohmic value when it gets krumt. Made
of Resistive Carbon technology, silver. Typical
range 10-80kOhm
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Light
Light is a form of electromagnetic radiation
Wavelength/ Frequency
c
?
f
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Photoconductive Cell (Photocell)
Photoresistor Is a resistor that changes the
ohmic value depending of the light
intensity LDR Light Depending Resistor Made
of Cadmium sulfide (CdS), Cadmium selenide
(CdSe). Typical range 100-10,000 Ohm
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Photo Diode
Photo Diode When a current is flowing thru it
will behave as a voltage source depending of
the light. The Principe is the photovoltaic, as
it is used in solar cells. Made of Silicon.
(Semiconductor) Linearity Good in a relative
large range. Low noise
NB Also available as a transistor. A transistor
is a semiconductor we later will work with.
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Photocell connected to the Teleo Device
- The principle is a voltage divider. - The
series connection of a photocell and a resistor
from 5V to ground(0V)
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Choosing the Resistor

• Choose in the range where the sensor is used
• Show example

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Switch- and Reflector Module
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Interruption and Reflector Module in Use
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Tilt Sensor
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Electrical Set Up of Tilt Sensor
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Oscilloscope
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Oscilloscope Measurements
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Exercise 1

• Design a small keyboard using Force Sensors
• Design opportunities
• Mapping
• Time
• Amplitude
• Electrical design

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Exercise 2

• Test the Bend Sensor with your multi meter.

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References

• Joseph arr Electronic Circuit Guidebook, Sensors
• Kurt Bodi Analog og digitalteknik
• James W. Dally Instrumentation for engineering
  measurements