3. An Introduction to Sensors and Transducers
The words 'sensor' and 'transducer' are both widely
used in the description of measurement systems
The word 'sensor' is derived from entire meaning
'to perceive' and 'transducer' is from transducer
meaning 'to lead across'.
TRANDUCERS
4. A dictionary definition of 'sensor' is `a device
that detects a change in a physical stimulus and
turns it into a signal which can be measured or
recorded;
A corresponding definition of 'transducer' is
'a device that transfers power from one system
to another in the same or in the different form'.
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5. A sensible distinction is to use 'sensor' for
the sensing element itself and 'transducer'
for the sensing element plus any associated
circuitry.
All transducers would thus contain a sensor and
most (though not all) sensors would also be
transducers.
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6. A transducer is a system that converts a physical
chemical or any natural quantity into a desired form
of energy as an indicator.
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13. 8 TYPE OF TRANSDUCERS
Electromagnetic
Electrochemical
Electromechanical
Electro acoustic
Photoelectric
Electrostatic
Thermoelectric
Radio acoustic
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14. Electromagnetic…
Antenna - converts electromagnetic waves into electric current and vice
versa.
Cathode ray tube (CRT) - converts electrical signals into visual form
Fluorescent lamp, light bulb - converts electrical power into visible light
Magnetic cartridge - converts motion into electrical form
Pick up (music technology) - converts motion into electrical form
Photodetector or Photoresistor (LDR) - converts changes in light levels into
resistance changes
Tape head - converts changing magnetic fields into electrical form
Hall effect sensor - converts a magnetic field level into electrical form only.
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16. Electromechanical…
Electroactive polymers
Galvanometer
MEMS
Rotary motor, linear motor
Vibration powered generator
Potentiometer when used for measuring position
Load cell converts force to mV/V electrical signal using strain gauge
Accelerometer
Strain gauge
String Potentiometer
Air flow sensor TRANDUCERS
17. Micro-Electro-Mechanical Systems (MEMS) is the integration of mechanical
elements, sensors, actuators, and electronics on a common silicon substrate
through microfabrication technology.
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18. Electro acoustic…
Geophone - convert a ground movement (displacement) into voltage
Gramophone pick-up
Hydrophone - converts changes in water pressure into an electrical form
Loudspeaker, earphone - converts changes in electrical signals into acoustic
form
Microphone - converts changes in air pressure into an electrical signal
Piezoelectric crystal - converts pressure changes into electrical form (and
electrical signals into acoustic/mechanical form)
Sonar transponder
Tactile transducer TRANDUCERS
19. WHAT IS ACOUSTIC?
Acoustics is the interdisciplinary
science that deals with the study of
sound, ultrasound and infrasound (all
mechanical waves in gases, liquids, and
solids).
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20. Photoelectric….
Laser diode, light-emitting diode - convert electrical power into forms
of light
Photodiode, photoresistor, phototransistor, photomultiplier tube -
converts changing light levels into electrical form
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21. Electrostatic….
Electrometer:An electrometer is an electrical instrument for
measuring electric charge or electrical potential difference. There
are many different types, ranging from historical hand-made
mechanical instruments to high-precision electronic devices. ...
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22. Thermoelectric….
RTD Resistance Temperature Detector
Thermocouple
Peltier cooler :A peltier cooler is a cooler
that uses a peltier element (TEC). Peltier
coolers consist of the peltier element itself,
and a powerful heatsink/fan combination to
cool the TEC.TRANDUCERS
27. PROBLEM: Department of
histology in a major hospital
needed a peltier cold plate to
freeze tissue samples for
examination.
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28. The Histology Division of the Department of Pathology places Tissue
SOLUTION:
samples from biopsies into a small block and fills it with wax. Several of these
samples are then placed on one of the PELTIER COOLER cold plates to "pull the
heat" out of the wax so it gets really hard. The near-frozen samples are then shaved
down to the desired section (slice) using a Microtome (in picture). The thin sections
are then placed in the water bath to warm up the remaining wax in order to remove it
and then place the section on a slide for examination.
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31. TRANDUCER IN ULTRA SOUND…..
A device that produces sound waves that bounce off
body tissues and make echoes. The transducer also
receives the echoes and sends them to a computer
that uses them to create a picture called a
sonogram. Transducers (probes) come in different
shapes and sizes for use in making pictures of
different parts of the body. The transducer may be
passed over the surface of the body or inserted into
an opening such as the rectum or vagina.
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32. A variety of ultrasound generation
mechanisms have been developed
by utilizing piezoelectric,
capacitive, laser- based, and
electromagnetic phenomena
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33. Ultrasound operates on the same principle as the
other characterization methods also based upon
wave- material interaction phenomena. These are:
Optical, X-ray, infra-red, Raman spectroscopy,
nuclear magnetic resonance, neutron, g-ray, mass
spectrometry, etc. By propagating a wave in a given
medium, useful information about the medium can
be generated by analyzing the transmitted or
reflected signals. Ultrasound differs from other
wave-based methods because it does not require
sample preparation; is non-hazardous; provides the
means to determine mechanical properties,
microstructure, imaging, & microscopy; is portable;
and is cost-effective
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38. MEASUREMENT
MEASURED PARAMETERS APPLICATIONS
CATEGORY
Time Domain Times-of-Flight and Velocities of Longitudinal, Shear, and
Surface Waves
Density, Thickness, Defect Detection, Elastic
and Mechanical Properties, Interface
Analysis, Anisotropy, Proximity &
Dimensional Analysis, Robotics, Remote
Sensing, etc.
Attenuation Fluctuations in Reflected and Transmitted Signals at a Given
Domain Frequency and Beam Size
Defect Characterization, Surface and
Internal Microstructure, Interface Analysis,
etc.
Frequency Domain AtFrequency-Dependence of Ultrasound tenuation, or
Ultrasonic Spectroscopy
Microstructure, Grain Size, Grain Boundary
Relationships, Porosity, Surface
Characterization, Phase Analysis, etc.
Image Domain Time-of-Flight, Velocity, and Attenuation Mapping as
Functions of Discrete Point Analysis by Raster C-Scanning or
by Synthetic Aperture Techniques
Surface and Internal Imaging of Defects,
Microstructure, Density, Velocity,
Mechanical Properties, True 2-D and 3-D
Imaging.
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Table 1: Categories of Ultrasonic Measurements and their Applications.
43. WHAT IS SPIROMETER?
A spirometer is an apparatus for
measuring the volume of air inspired and
expired by the lungs.
The spirometer records the amount of air
and the rate of air that is breathed in and out
over a specified time.
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49. MILLER,S QUADRANT…….
RESTRICTIVE NORMAL
120
F
E INS √
100
V
60
COMBINED OBSTRUCTIV
F 40 EXP
V
C
BOTH
% 20
0
20 40 80 100
120
FVC/FVCref %
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51. PRESENT TRANSDUCER USED IN SPIROMETER……
TURBINE TRANDUCERS
actually a
rotating vane,
this spins, the
revolutions
are counted
as they break
a light beam
TRANDUCERS
52. OTHER PRESENT TRANDUCERS USED…
Fleisch-pneumotach
Lilly (screen) pneumotach
Turbine (actually a rotating vane, this
spins, the revolutions are counted as they
break a light beam)
Pitot tube
Hot-wire anemometer
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54. A device for electromechanical stimulation and testing of
hearing in which an electromechanical transducer
transmits audiologic signals as mechanical deflections via
a coupling element from the outside, noninvasively
through the external auditory canal, by direct mechanical
coupling with the manubrium of the malleus to the
ossicular chain. In preferred embodiments, by suitable
selection of the transducer principle disruptive magnetic
stray fields and acoustic stimulation by sound
transmission to the contralateral ear, which is not being
examined, are prevented.
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