Transducers Flashcards
This material is responsible for converting sound energy into electric energy and vice versa?
PZT (lead zirconate titanate), aka ceramic, active element, or crystal.
How is the PZT crystal distorted to create sound?
You apply voltage to distort the crystal. Voltage in, sound out.
What is the Curie Temperature?
The temperature, 365 degrees celsius, is used to polarize the active element.
What does the Curie temperature do?
Heating the PZT crystal to the Curie temperature along with applying a current, aligns the magnetic domains and polarizes the element.
Can you autoclave a transducer?
No, heating the element above the Curie temperature will depolarize the crystal destroying its properties.
What are the components of the transducer?
PZT, matching layer, backing material, acoustic insulator, wire, electric shield, and the case.
What is the matching layer responsible for?
The matching layer steps down the impedance from the probe to tissue.
How do you measure the matching layer?
The matching layer is 1/4 wavelength thick
How do you measure the PZT element?
The active layer is 1/2 wavelength thick
What is the backing layer responsible for?
The backing layer dampens the signal decreasing the sensitivity.
How does the backing layer dampen sound?
The backing layer reduces ringing which decreases the SPL giving rise to better axial resolution.
Is resolution the maximum distance two objects can be apart and still be distinguishable?
False. Resolution is the MINIMUM distance apart two objects can be and still be distinguished.
What is axial resolution?
Axial resolution is responsible for the detail found in an image. It’s the ability of a system to display two structures that are very close together parallel to the sound beam.
What are some synonyms for axial resolution?
Longitudinal, radial, range, or depth.
What is the biggest affect on axial resolution?
SPL. Shorter pulses can get between closely aligned objects.
