Schematics for 5 MHz ultrasonics?

Hi,

I am trying to find more information on ultrasonics, especialliy on
how to control the voltage pulse on the transducers, and how to read
back and anlyse the data. Does anyone have experience or leads?

Regards,
Pieter Hoeben
email:

 

Are you sure you mean 5mhz????

 

I guess there must be some sort of transducer that goes that high,
only thing that strikes me as having any chance is putting the
electricity straight through the air. I've not heard of 5MHz
ultrasonics before either.


Regards, NT

 

SAW filter, surface acoustic wave

 

Medical ultrasound uses frequencies that high and much higher. I've
been building my own transducers for 8.5 and 20 MHz using ordinary piezo
material.

Jim

 

5MHz is pretty typical for modern diagnostic medical ultrasound, which
is transmission into water, rather than air. The machine that make
nice pictres of my aortic valve seems to work around that sort of
frequency.

When I was working on phased array ultrasound in 1976-79 at EMI
Central Research, I spent some time glueing together my own 2MHz
single unit transducer out of a layer of some odd piezo-electric
crystal that we bought from Philips, and a couple of layers of epoxy
resin bonded tungsten power to produce quarter-wave matching layers to
get reasonable impedance matching into water.

Back then we had high hopes of poled stretched polyvinylidene fluoride
plastic film, which had an acoustic impedance a lot closer to water,
but I don't think that it ever did anything much for medical
ultrasound.

 

The field is very specialized and there will be no intelligible
literature accessible to an application engineer outside specific sensor
manufacturer application notes and technical support.

 

James Meyer wrote...

Wow. I've done some work making my own transducers at
5 and 10MHz, but the piezo disc was getting pretty thin.
20MHz, please Jim, tell us more. Spill the beans for us!

Thanks,
- Win

whill_at_picovolt-dot-com

 

Piezo sheets from http://www.piezo.com/en-us/dept_40.html. I was
making little 3x7mm 'ducers. Scribe the sheets with a sharp tungsten
carbide tool and break them just like a pane of glass or use a
lapidary saw with a thin diamond blade. Browse the whole site for
lots of really good info.

Get their soldering kit too. It's got flux and solder for the
nickle electrodes. They even throw in a small piece of piezo to play
with. They don't guarantee what material you'll get, but the sample I
got was the same as what I needed for the 8.5 MHz 'ducers.

Jim

 

Jim Meyer wrote...

Good going, Jim, those are the beans I had in mind!

Thanks,
- Win

whill_at_picovolt-dot-com

 

Nobody else here saw the Sci Am article "KiloMegacycle
Ultrasonics" (6/63)?

You stick a big piece of quartz into a hole in a cavity
resonator and feed it lots of RF. IIRC they were beaming 3
GHz around their lab.

Mark L. Fergerson

 

Nobody else here saw the Sci Am article "KiloMegacycle
Ultrasonics" (6/63)?

You stick a big piece of quartz into a hole in a cavity
resonator and feed it lots of RF. IIRC they were beaming 3
GHz around their lab.

Mark L. Fergerson
[/QUOTE]
Iv been collecting Sci Amer from 60s so Ill go and look.
In '61 I started work on Mil Sonar and by 70s had converted to Quartz
resonators.
Quartz has a low coupling coefficient so needs a lot of drive voltage at
GHz the inherent acoustic Q is only a few 1000. Thats why SAWs are
limited in Q at GHz.
Lithium Niobate would be easier from a coupling coefficient point of
view.
YIG could be interesting.
I remember an air powered whistle that operated at the focus of a
parabolic mirror that ignited wool at a distance of some feet also an
Amateur Scientist .
Magnetostriction could well be the way for the amateur to proceed.

 

Yes, for measuring wall thickness of pipes

Pieter

 

EBay often has complete ultrasound thickness gages for sale. The prices
are often quite reasonable. I'll bet you could find one you could afford by
looking for a length of time less than it would take for you to build your own.

Jim