Lesson 12 Flashcards
What kind of wave is sound?
Mechanical
- not ionizing radiation
- not electromagnetic
What movement can sound do? (2)
- Converge
2. Diverge
What are 2 other names for transducer assembly?
- Probe
2. Scan head
What is the order of transducer assembly? (4)
- Case
- Damping material
- Element
- Matching layer
Transduce
Convert one form of energy into another
What happens if you change the shape of the transducer?
It creates sound through pressure
- happens so fast it creates ultrasound
AV
Alternating voltage
What does alternating voltage allow?
The thickness and thinness of an element to change
- creates a mechanical wave
When is AV used?
In doppler
What is the break down of piezoelectricity? (2)
- Piezo
- press - Elektron
- amber
What is being converted in piezoelectric effect?
Pulse of sound to voltage (echo)
What is being converted in reverse piezoelectric effect?
Voltage (echo) to a pulse for sound
What is a piezoelectric element also known as?
A crystal
What is 1 cycle of alternating voltage equivalent to?
2/3 cycles of a pulse
What does a longer alternating voltage mean?
A longer pulse
- doppler
What does returning echoes that affect the element create?
Voltage
Quartz
One of the first natural piezoelectric crystals
What are synthetic crystals made from? (4)
- Lead
- Zirconate
- Titanate
- Barium
What are piezo-electric elements usually made of?
Lead zirconate titanate
- PZT
How is PZT created?
It is placed in a strong magnetic field at a hight temp and it realigns its molecular dipoles and then cooled
What would happen if you brought the crystal back to the curie point but without the magnetic field?
It loses its electric properties and the dipoles will scatter
- not electric anymore
What happens during polarization of the piezo-electric elements?
The dipoles align
Curie point
The temperature in which the magnetic properties of a solid can be changed
What is the curie point of PZT?
350 deg C
When might you lose the electric properties of the probe?
If you put it in sterilizing solution
What do piezo-electric elements have?
Natural vibrational frequency
What does operating frequency depend on? (2)
- Propagation speed of the element
2. Thickness of the element
What kind of noise does a little bell make? (2)
- Higher pitch
2. Higher frequency
What kind of noise does a big bell make? (2)
- Lower pitch
2. Lower frequency
What can we use to adjust the transducer frequency?
Voltage frequency
What are we dealing with when we are using a pulsed wave?
Bandwidth
Multi-Hertz operation
2 or 3 frequencies on the same element
What does PRF of voltage also affect?
PRF of pulse
What is the relationship between PRF and depth?
Inversely proportionate
What happens to depth when PRF increases?
It decreases
Range ambiguity
Is a technique used with medium PRF radar to obtain range information for distances that exceed the distance between transmit pulses
- needed for doppler
