Flashcards in Lesson 12 Deck (36)
What kind of wave is sound?
- not ionizing radiation
- not electromagnetic
What movement can sound do? (2)
What are 2 other names for transducer assembly?
2. Scan head
What is the order of transducer assembly? (4)
2. Damping material
4. Matching layer
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
What does alternating voltage allow?
The thickness and thinness of an element to change
- creates a mechanical wave
When is AV used?
What is the break down of piezoelectricity? (2)
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?
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
What does returning echoes that affect the element create?
One of the first natural piezoelectric crystals
What are synthetic crystals made from? (4)
What are piezo-electric elements usually made of?
Lead zirconate titanate
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
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)
1. Propagation speed of the element
2. Thickness of the element
What kind of noise does a little bell make? (2)
1. Higher pitch
2. Higher frequency
What kind of noise does a big bell make? (2)
1. Lower pitch
2. Lower frequency