Piezo Transducer

Piezo Transducer

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  To speed up the development of information industry in Chongqing Municipality has developed information industry, "1162" project, which includes an electronic chip production base will be built nationwide.

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Which is located in the West Wing Shapingba Microelectronics Industrial Park, an area of 10 square kilometers, will become a national electronic chip production base. In addition, the Chongqing Municipality "City Card" feature should be used next year to upgrade. City Council letter produced a special presentation on behalf of Chongqing "City Card" the latest development plan.

It is understood that "City Card" is the urban transport, communications, shopping and entertainment areas such as the use of IC cards for public consumption card rolled into one. With the completion of system construction within this year, Chongqing Municipality, "One Card" users will be developed to 60 million in areas such as buses, light rail, taxi, car parks, filling stations, welfare lotteries.

Next year will be extended to highways, shopping malls, leisure entertainment, and people are concerned about water, electricity, gas and other areas, card users will be developed into 1.5 million -250 million, and the achievement of the relevant product sales and services revenue 100 million yuan above, card spending by 20 billion yuan by 2010, the user is expected to reach 10 million cardholders.

What is the best Ultrasonic transducer?

1.Can a commercial (cheap) ultrasonic transducer having a center frequency of 40kHz be used to create ultrasonic waves of 18kHz to 2MHz.
2.I intend to create ultrasonic waves using a signal generator and an amplifier and I don`t know what to use as best transducer.
3.Can a piezo tweeter be used?
4.Can the ultrasonic waves be concentrated using a parabola?
5.I want to be able to create cavitation in a fluid in a test tube and I thought that the best way would be to use high powered ultrasonic waves. How can I calculate the correct lenght of a tube given a specific frequency?

Thanks.

a1)
O.K. what your talking about is the bandwidth of the transducer. A transducer will have a central frequency like you say (in this case 40khz) but it will also have a bandwidth. The bandwidth is the frequency range the transducer can operate within which will be less power output than the central frequency, however the power loss will only be limited. A transducer can usually operate outside of the bandwidth however the power loss will usually be more. The frequency range you are hoping to get from this 40khz transducer is quite high. I think it would be unlikely that it could do this range. If it can do this range, it would be very unlikely that the bandwidth would cover this range.
*note - you are not always able to get this bandwidth information before purchasing a transducer especially with a cheap transducer.

a2)
Choosing a transducer is very specific to the application which you are hoping to use it for. Some examples of questions to ask are; whether you need a water coupled transducer or an air coupled, whether the transducer will run in chirps/ pulses -ie. reduced duty cycle -(like for non destructive testing) or constant output, whether you require a narrow beam or a wider beam angle (like for distance measurement) or maybe you require the entire transducer to resonate (eg. bolted langevin transducer), how wide bandwidth you require, whether you will be attaching a horn (to concentrate and/or direct the output), whether it is a high output application or relatively low output, what the specific application is, what type of amplifier you are using (better to select the transducer before selecting the amp) - best if you can select a transducer that will run of a cheap amp like an pro audio amp if you want to save money, whether you require an industrial transducer or whether you could achieve your goals using a standard acoustic transducer like a loudspeaker.

a3)
piezoelectric and magnetostrictive are two different types of transducers. You could use piezo, it tends to have a wider bandwidth also, and it can also be used for very high frequencies. A standard tweeter would be difficult to use because it is only designed to only cover the audio range of up to 20khz. Also the output graph is something to consider. For example a tweeter may be rated to 20khz with a power output (spl) of 130db, but the output graph or output may drop off substantially at only 14khz. It is still rated to 20khz, but the power is very low at this level. I think that the frequency range you are trying to get is very wide, and maybe you will need an industrial transducer. As you appear to be trying to save money, maybe you can find a small or cheaper industrial transducer which can cover your application.

a4)
Do you mean a parabolic horn? Sometimes a horn is used to concentrate sound waves from a transducer. The transducer would have to be designed to accommodate a horn. A number of different types of horns are available. You would have to research this for your application. Professionally build horns can be very expensive. Maybe you can find a cheap copy somewhere, although it would be unethical to buy a direct copy of a more expensive design.

a5)
If you are serious about this you will have to do some research more than yahoo answers.