Home
Flashcards
Preview
ch 9 transducers
Home
Get App
Take Quiz
Create
transducer
device that converts one form of energy into another
transducer transmission
electrical energy to mechanical
transducer reception
mechanical to electrical
2 dimensions of crystal
width (diameter)
thickness (a/p)
reverse piezoelectric effect
definition and syn
property of a material to change shape when an electrical voltage is applied to it
Happens on TRANSMISSION
ferroelectric
piezoelectric effect
property of a material to create a voltage when mechanically deformed (pressure is applied)
Happens on RECEPTION
natural piezoelectric materials
quartz
tourlamine
rochelle salts
man made piezoelectric materials
PZT- Lead Zirconate Titate
Barium Titinate
ends in "ate"
synonyms for piezoelectric material
crystal
active element
ceramic
polarization
to make piezoelectric by putting under a high temperature
place in an electrical field
ions line up + with + - with -
cool rapidly and ions stayi n the same place
curie point
temperature to polarize or depolarize
depolarization
if piezoelectric material is put back in high heat
transducer sterilization/disinfecting
autoclave- heat sterilization
disinfect- with chemicals - Cidex
case
metal or plastic
insulates internal components from damage
insulates pt from shock
electrical shield
think metallic barrier lining inside of case
prevents spurious signals in air from entering transducer
and contaminating clinical electrical signals
acoustic insulator
thin barrier of cork or rubber that internal components from the case
prevents vibrations from inducing electrical voltage in the pzt
pzt or active element
crystal itself
shaped like a coin
characteristics of sound beam related to dimensions of element
PZT is 1/2 wavelegnth thick
wire
provides electrical connection btwn PZT and us system
matching layer
infront of PZT
increases efficiency of sound energy transfer btwn element and body
protects active element
1/4 wavelegnth thick
backing/damping material
back of element
reduces ringing of pulse
made of epoxy resin impregnated with tungsten filaments
restricts pzt deformation
creates short duration of pulse
enhances axial resolution
impedance of PZT compared to skin
pzt impedance 20xs greater than skin
would reflect right back if no matching layer
decreasing order of impedance
pzt
matching layer
gel
skin
backing material characteristics
high degree of sound absorption
acoustic impedance similar to PZT
consequences of backing material
decreased sensitivity
wide bandwidth
low quality factor
decreased sensitivity
less able to convert low level sound reflections into meaningful electrical signals in reception
bandwidth
the range or difference between the highest and lowest frequencies in the pulse
short pulse
? bandwidth
wide
backing material and bandwidth
wide bandwidth
continuous wave and bandwidth
narrow bandwidth
quality factor
unitless number related to bandwidth
qf = main frequency/ bandwidth
quality factor and bandwidth
inversely related
wide bandwidth probe has...
narrow bandwidth probe has..
wide= low quality factore
narrow= high quality factor
imagine probes have high bandwidth and
low q factor
q factor is directly related to
pulse legnth
short and low
long and high
duty factor of continuous wave
100%
2 elements of continuous wave
always sending and always recieving
no image produced
continuous wave has no
damping or listening time
sound frequency of cw probe
= electrical frequency
imaging transducers
high wide bandwidth
low Q
q factor number
unitless and less than 1
Author
rbeacr
ID
141830
Card Set
ch 9 transducers
Description
transducers
Updated
3/15/2012, 9:33:34 PM
Show Answers
Home
Flashcards
Preview