Lesson 14

Question 1

What are the 4 different componets to a transducer?

Answer 1

1. Lens
2. Matching layer
3. Single crystal element
4. Backing material
   - damping

Question 2

What are elements?

Answer 2

Crystals

Question 3

What happens to beam profiles in transducers?

Answer 3

They go in and out at the same time

- no pulses

Question 4

What is happening to beam width in pulse waves?

Answer 4

They are changing

- naturally shortens and widens again

Question 5

Where is the natural focus on a pulse wave beam profile?

Answer 5

At the smallest point

Question 6

Where is the near zone?

Answer 6

Between the focus point and the transducer

- minimun beam width

Question 7

Where is the far zone?

Answer 7

From the focus point and onwards

Question 8

What are 2 other names for the near zone?

Answer 8

1. Fresnel zone

2. Near field

Question 9

What happens to the beam width when increasing distance from the transducer in the near field?

Answer 9

It decreases

Question 10

Beam convergence

Answer 10

Light rays comes together (converges) after reflection and refraction at a single point known as the focus

Question 11

What are 2 other names for far zone?

Answer 11

1. Fraunhofer zone

2. Far field

Question 12

What happens to the bandwidth with increasing distance from the transducer in the far-field?

Answer 12

It increases

Question 13

Beam divergence

Answer 13

When beams of light move away from each other after passing the focus point and going into the far field

Question 14

Aperture

Answer 14

For a single disk transducer, this is the element size or width of group of elements

• opening
• top by the transducer

Question 15

What does beam width change with?

Answer 15

Depth

Question 16

What does beam width affect? (2)

Answer 16

1. Resolution of signal at that depth

2. Intensity of the sound beam at that depth

Question 17

What happens to the resolution with a more narrow beam width?

Answer 17

It gets better

Question 18

When is intensity the strongest?

Answer 18

At a smaller focus point

Question 19

What is considered to be uniform?

Answer 19

Power

- equal at any point along the beam

Question 20

What is the formula for beam width (Wb) at the focus?

Answer 20

1/2 the aperture size

Question 21

NZL

Answer 21

Near zone length

Question 22

What is NZL determined by? (2)

Answer 22

1. Size of the element
   - aperture
2. Operating frequency

Question 23

What happens to NZL if aperture increases?

Answer 23

It increases

Question 24

What happens to NZL if frequency increases?

Answer 24

It increases

Question 25

Is there a far zone length?

Answer 25

No

Question 26

What happens to NZL if aperture goes up?

Answer 26

It goes up by 2

- aperture^2 proportional to NZL

Question 27

What is the near zone length the same length is?

Answer 27

The focal length

Question 28

What is a footprint?

Answer 28

Width of the probe

Question 29

What do you need to do if you want a high frequency disk transducer to look at superficial structures?

Answer 29

Adjust the focus because intensity is highest at the focus and the resolution will be better

Question 30

Do we want a large footprint or a small one when looking at smaller structures?

Answer 30

Smaller footprints because your NZL will be shorter and your focus will be higher

Question 31

What kind of footprints do higher frequency transducers have?

Answer 31

Smaller footprints

Question 32

Why do we adjust the focus?

Answer 32

Because the resolution is best when the focus is smallest

Question 33

Smallest beam width (2)

Answer 33

1. Strongest intensity
   - will pick up more signals
2. Better resolution with smaller beam width

Question 34

Where is focusing only accomplished?

Answer 34

In the near zone

Question 35

What happens to the focus when the curve increases?

Answer 35

You get a closer focus

- mechanical focusing