Physics Final

Question 0

Piezoelectric Material

Answer 0

Material which converts sound to electricity and vice versa

Called: Piezoelectric, ferroelectric

Synonyms-Ceramic, active element, crystal

Question 1

Transducers

Answer 1

Device that converts one form of energy into another

2 functions:
Transmission
Reception

Question 2

Piezoelectric Effect

Answer 2

Distort a PZT crystal you produce voltage.
Put voltage into a crystal you distort crystal

• Voltage in >Sound out
• Sound In >Voltage out

Question 3

Curie Temperature

Answer 3

Temperature at which substance can be polarized, 365 degrees celsius

Question 4

Polarizing PZT

Answer 4

Random, Before polarization, polarization in DC field, Rememnent polarization after field removed

Heat PZT above curie temp. Apply current to align magnetic domains polarize element, then cool down.

Question 5

7 components of ultrasound transducer

Answer 5

1. Wire
2. case
3. PZT
4. Matching layer
5. backing material
6. acuostic insulator
7. electric shield

Question 6

Why matching layers?

Answer 6

must step down the impedance to avoid huge echo at the transducer face

• increases the efficiency of sound energy transfer between the active element and body.
• protects active elements
• 1/4 wavelength thickness

Question 7

PZT

Answer 7

• active element, coin shaped
• simple probe
• half wavelength thick

Lead Zirconate titanate

Question 8

Matching Layer

Answer 8

• 1/4 wavelength thick
• positlond in from of PZT
• increase efficiency of sound energy transfer between the active element and body
• protects active element

Question 9

Backing Material

Answer 9

Damping element
reduces crystal ringing=short pulse (SPL)=
better axial resolution
Consequences: decrease sensitivity, doesn’t allow signals to move, less able to convert low level sound reflections into meaningful signals

Wide BW = Low QF