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Flashcards in Lesson 12 Deck (36)
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1

What kind of wave is sound?

Mechanical
- not ionizing radiation
- not electromagnetic

2

What movement can sound do? (2)

1. Converge
2. Diverge

3

What are 2 other names for transducer assembly?

1. Probe
2. Scan head

4

What is the order of transducer assembly? (4)

1. Case
2. Damping material
3. Element
4. Matching layer

5

Transduce

Convert one form of energy into another

6

What happens if you change the shape of the transducer?

It creates sound through pressure
- happens so fast it creates ultrasound

7

AV

Alternating voltage

8

What does alternating voltage allow?

The thickness and thinness of an element to change
- creates a mechanical wave

9

When is AV used?

In doppler

10

What is the break down of piezoelectricity? (2)

1. Piezo
- press
2. Elektron
- amber

11

What is being converted in piezoelectric effect?

Pulse of sound to voltage (echo)

12

What is being converted in reverse piezoelectric effect?

Voltage (echo) to a pulse for sound

13

What is a piezoelectric element also known as?

A crystal

14

What is 1 cycle of alternating voltage equivalent to?

2/3 cycles of a pulse

15

What does a longer alternating voltage mean?

A longer pulse
- doppler

16

What does returning echoes that affect the element create?

Voltage

17

Quartz

One of the first natural piezoelectric crystals

18

What are synthetic crystals made from? (4)

1. Lead
2. Zirconate
3. Titanate
4. Barium

19

What are piezo-electric elements usually made of?

Lead zirconate titanate
- PZT

20

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

21

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

22

What happens during polarization of the piezo-electric elements?

The dipoles align

23

Curie point

The temperature in which the magnetic properties of a solid can be changed

24

What is the curie point of PZT?

350 deg C

25

When might you lose the electric properties of the probe?

If you put it in sterilizing solution

26

What do piezo-electric elements have?

Natural vibrational frequency

27

What does operating frequency depend on? (2)

1. Propagation speed of the element
2. Thickness of the element

28

What kind of noise does a little bell make? (2)

1. Higher pitch
2. Higher frequency

29

What kind of noise does a big bell make? (2)

1. Lower pitch
2. Lower frequency

30

What can we use to adjust the transducer frequency?

Voltage frequency