Transducers

Question 1

Direct Piezoelectric Effect

Answer 1

When acoustic PRESSURE is applied to some materials, they will deform and create ELECTRICAL energy.
DIRECT RECEPTION!

Question 2

Matching Layer ideal thickness:

Answer 2

1/4 wavelength

Question 3

Purpose of Damping Material:

Answer 3

Improves AXIAL, SPACIAL, DETAIL resolution.

Question 4

The main frequency is the:

Answer 4

Center or Operating Frequency.

Question 5

Broad bandwidth:

Answer 5

Pulse with MANY frequencies present.

Question 6

Narrow bandwidth:

Answer 6

Pulse with FEW frequencies present.

Question 7

The SHORTER the PULSE, the ______ frequencies that are present, the ______ the bandwidth.

Answer 7

MORE, WIDER

Question 8

Quality Factor

Answer 8

Number that indicates the extent that transducer can operate at the center or main frequency.
UNITLESS NUMBER!

Question 9

Pulsed transducers = _____ Q Factor

Answer 9

LOW

Question 10

Continuous wave transducers = ______ Q Factor

Answer 10

HIGH

Question 11

Quality Factor Equation:

Answer 11

Q FACTOR = OPERATING (MAIN) FREQUENCY/
BANDWIDTH
(EST of Q Factor - # of cycles in pulse)

Question 12

Can operate at more than one center frequency:

Answer 12

Multihertz Transducer.

Question 13

The _____ _______ can be chosen w/Multihertz Transducers w/broad bandwidth.

Answer 13

Operating frequency

Question 14

Multihertz Transducers Pro:

Answer 14

Able to switch frequency w/o changing transducers. (User adjustable)

Question 15

The TWO factors that determine Operating Frequency:

Answer 15

1. Propagation speed in piezoelectric material.

2. Thickness of crystal.

Question 16

Operating Frequency Equation:

Answer 16

Fo = SPEED/ (2x THICKNESS)

Operating Frequency =
Propagation speed in Piezoelectric Material/
2x Thickness of the Piezoelectric Material

Question 17

RELATIONSHIP:

Propagation speed and Operating Frequency.

Answer 17

DIRECTLY RELATED.

Question 18

RELATIONSHIP:

Thickness of material and Operating Frequency.

Answer 18

INVERSELY RELATED.

Question 19

Typical thickness of piezoelectric material:

Answer 19

1/2 wavelength of sound in material.

.2 - 1 mm

Question 20

A shorter dampened pulse has a LOWER/HIGHER Q-factor.

Answer 20

LOWER.

Question 21

Q-factor is:
INVERSELY related to: _______ &
DIRECTLY related to _______.

Answer 21

BANDWIDTH.

PULSE LENGTH.

Question 22

Transducer w/3 MHz main freq. produces a sound pulse w/freq. ranging from 1 MHz - 5 MHz. The BANDWIDTH (RANGE OF FREQ) in this pulse is:

Answer 22

4 MHz

5 MHz - 1 MHz = 4 MHz

Question 23

Short duration events are usually _______ bandwidth (broadband).

Answer 23

WIDE.

Question 24

The ______ the Q-factor, the _______ the images (OR ______ ______).

Answer 24

LOWER.
BETTER
AXIAL RES.

Question 25

Electrical frequency =

Answer 25

Acoustic frequency.

Question 26

Speed of sound in PZT and the frequency of sound are _______ related.

Answer 26

DIRECTLY.

Question 27

Thinner active elements create pulses:

Answer 27

w/HIGHER frequency and SHORTER wavelength cycles. (and vise versa)

Question 28

PZT thickness and frequency are:

Answer 28

INVERSELY related.

Question 29

NZL is also called:

Answer 29

FOCAL DEPTH.