High frequency Transducer Question
amdx
frequency transducers (~ 600Khz)
We drove them at anti resonance, This gave us a higher impeadance to drive,
lowering the current through our
transformer and series inductor. But I also remember the fellow saying
something about the beam pattern being
different between resonance and antiresonance. These transducers were run in
an a water soution.
Can anyone describe how the wavefront would be different between resonance
and antiresonance?
Or, how would the movement of the front of the transducer be different.
Link to a plume
http://i395.photobucket.com/albums/pp37/Qmavam/Plume.jpg
This plume is caused when 600Khz sound hits the water/air interface.
This is approx. 1KW from a 2" transducer.
Mike
answerman
news:8a391$4a9ea077$d8baf3ed$32...@KNOLOGY.NET:
I don't have an answer, but here are some points that may be relevant.
The resonant frequency (electrical impedance minimum) is established
primarily by a mechanical (thickness mode) resonance which, for piezo
ceramics is very high Q, even in water. So, when you drive a thickness-
mode piezoelectric transducer at resonance, you have the benefit of a
high-Q mechanical filter to limit the amount of energy goes into exciting
higher-order modes during onset and offset transients and/or if the
excitation is a square wave, as opposed to being sinusoidal. If you
drive the transducer at its anti-resonance, you lose the benefit of the
mechanical filter, and the effect of higher order modes would show up if
you are measuring the beam pattern broadband. However, if you are using
sinusoidal steady-state excitation, I don't see why there should be a
difference in the radiation patterns at resonance vs anti-resonance.
The only other thing that I can think of is that there is a radial-mode
resonace that is near the thickness-mode anti-resonance, in which case a
beam pattern difference would show up even with sinusoidal steady-state
excitation.
Salmon Egg
"amdx" <am...@knology.net> wrote:
Please be more specific, To me resonance means a minimum impedance while
antiresonance means maximum impedance as functions of frequency, Maximum
power transfer implies that a low impedance voltage source be used for
the former and a high impedance current source for the latter. If the
resonance or antiresonance arises from a mechanical mode of vibration,
these two mode shapes can be very different from each other. If you are
using circuit elements to impedance match, you will be driving off of
the mechanically resonant peak. In either case, having different
excitation patterns should not be a surprise.
Bill
--
Private Profit; Public Poop! Avoid collateral windfall!
Salmon Egg
> This plume is caused when 600Khz sound hits the water/air interface.
> This is approx. 1KW from a 2" transducer.
Many years ago, I was working with quartz crystal transducers immersed
in water at about 5 MHz. The momentum transfer is intrinsic to the sound
wave. In many ways is in mathematical analogy to light pressure in light
waves. It has nothing do do with the air gap if any except for the
effects of mismatch on the momentum density.
amdx
The responses I received were reasonable, But I was not impressed
with the quantity received in a 55 hour period.
And the beat goes,
Mike
answerman
@KNOLOGY.NET:
Ignoring the fact that you are obviously an ingrate, what was lacking in
the response that I provided, and what specifically would it take to
"impress" someone with your mentality?
amdx
"answerman" <answerman@home> wrote in message
news:_5SdnWypcvNOJjzX...@giganews.com...
> "amdx" <am...@knology.net> wrote in news:9eb8$4aa1abea$18d6b40c$23293
> @KNOLOGY.NET:
>
>> I posted the question just to see if there would be any response!
>> The responses I received were reasonable, But I was not impressed
>> with the quantity received in a 55 hour period.
>> And the beat goes,
>> Mike
>>
>
>
> Ignoring the fact that you are obviously an ingrate,
>
I don't know what made you think that.
>what was lacking in the response that I provided,
I said your response was reasonable!
>and what specifically would it take to
> "impress" someone with your mentality?
OK, ok, I'm impressed with your answer to my post.
I guess the fact that I only got one flame is evidence that this group is
dying :-)
Have a happy day!
Mike :-)
amdx
"amdx" <am...@knology.net> wrote in message
news:5f272$4aa1cb8f$18d6b40c$22...@KNOLOGY.NET...
Mike
Peter Larsen
> I posted the question just to see if there would be any response!
> The responses I received were reasonable, But I was not impressed
> with the quantity received in a 55 hour period.
_You_ then failed the test ... O;-) ... the group it appears passed with
flying colours and with good patience for a question that had the appearance
of being slightly silly, yet they gave it the benefit of the doubt.
> And the beat goes,
> Mike
Kind regards
Peter Larsen