Physics of Ultrasound: Transducers - Segment #1

[@kenrolt8072]

There are two correct answers to this question: B and C. Answer C, the one you gave, has to do with the thickness mode vibration of the slab. Answer B, has to do with the radial mode of the slab. Since the diameter is usually larger than the thickness for a "slab", then the fundamental radial mode resonance will occur at a lower frequency than the fundamental thickness mode resonance. As an example, a transducer might have a 1 MHz (fundamental) radial mode and a 3 to 4 MHz (fundamental) thickness mode. I use the term fundamental because there are higher order modes for each. The thickness modes occur in odd multiples of a half-wavelength (in the slab), i.e. 1, 3, 5.... while the radial modes occur in a noninteger sequence. These are details that most ultrasound people don't know, but they are nevertheless correct. Thank you for making the lecture series.

[@PunmasterSTP]

Transducers? More like "Transcendental!" This lecture series is immensely helpful and educational, and thank you so much for putting everything together and uploading it.

[@08Ultrasonic]

Yes there is. Look up a mechanical transducer. In a medical environment they're usually used to scan between the ribs.

[@mohamedabdalla6479]

Thank you. Very clear

[@fernandohood5542]

What matching material could I use for transmission through metal.

[@mkbsatish]

poling of a piezoelectric material is done below and close to the curie temperature and not above the curie temperature

[@paulaburke5586]

heating up to 365 is polarization, heating above is depolarization

[@PunmasterSTP]

I'm not entirely sure, but I think the idea is that you heat something up above the Curie temperature, apply a high voltage to it and then cool it back down, resulting in polarization. I'm not sure if there is a specific name for this process, but I've been trying to look it up and I've been coming up empty-handed...

[@hajikhanom]

Dear Dr. Chan, Thank you very much for your very good explanation about the physic of ultrasounic. I have aquestion about imaging. is that posible to make ultrasounic- image using only one transducer? for emample we have a key and we will make image from this key with 3 mm resolution, can we use only transducer to make a pic from the key or we must have more than one transducer. I'd be very greatful if you could answer me. Best regard

[@PunmasterSTP]

I apologize if I am misinterpreting your question, but I think that almost all ultrasound images are made using a single transducer. However, depending on the ultrasound mode you'd like to use, you might use a transducer with one piezoelectrical element or a transducer with two piezoelectrical elements.

[@ig090]

Great lectures!

[@kitzayitzay]

heaps helpful! thanx!

[@paulaburke5586]

or more detailed-- Activation is through: heating above** Curie temperature (Tc for PZT = 365’C specifically), applying high voltage across the element, partial alignment of charges (net dipole moment) = polarization. When it cools down (slowly going below 365) that is when the transducer's dual action can be seen.

[@PunmasterSTP]

I know it's been a long time, but I wanted to say that I came across your comment and I found it really helpful; I was scratching my head for a while! I tried to find sources describing this process online, but it was hard to find anything that described the process of heating something above the Curie temperature, applying a voltage and then cooling it back down. Does this process have a specific name, and/or could you point me to a good resource? Thank you!

[@Paivimehr]

lifesaver. I missed my class.

[@PunmasterSTP]

I know it's been a long long time, but I was just curious. How did the rest of your class go, and did you take the SPI exam? How have things been going over the years?

[@Fadeel14]

where can i get these slides plz

[@bluetable933669]

other parts??

[@tomr1961]

I'm sorry but check mark 3 and 4 seem to contradict each other. Both seem to say to heat above Tc will polarization or depolarized. Witch is it.

[@PunmasterSTP]

I'm not entirely sure, but I think the idea is that you heat something up above the Curie temperature, apply a high voltage to it and then cool it back down, resulting in polarization. I've been trying to look this up but I'm still confused...

[@tarunkumarpaluri1668]

This video needs more clean and keen breifing

[@novaali7439]

is there any one who took the spi exam already? I need some help.

[@PunmasterSTP]

I know this was years ago, but I just came across your comment and I was curious. How did your exam go, and how have things been going over the years?