• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 30 subscribers
  • Views 206 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

TDC1000: TDC1000

TDC1000: Transducer Sourcing and Calculating Resonant Freq in Thickness Mode

Pete Sampson
Prodigy 230 points
Part Number: TDC1000
Other Parts Discussed in Thread: PGA460, TUSS4470

Looking for piezo cermaic transducers for liquid level sensing if a few different freqs but having trouble finding them. I'm looking for a few different piezo ceramic disks with a high Q factor with resonant freqs in in the 40khz, 200khz, and 450-480khz. Do you have any suggestions on where to source these? I have already checked this out the TI List of example transducers. I've mostly been looking at piezo disks on Steminc which is references in some of the App Notes:

https://www.steminc.com/PZT/en/

However, that website is the single worst product website I've used and I haven't found a good alternative. They have no way to sort products by frequncey or mode of vibration. When you do find a product that will work after manually clicking on every option it's usually out of stock and also doesn't list parameters such as max drive voltage and max number of pulses for the piezo. Almost all the piezo disks on the site are listed as "Radial mode vibration application" and I'm looking for thickness mode vibration which for disk (as I understand it), should perform much better than radial mode because of the large surface area relative to the thickness making is more senative and easier to create sound pressure waves. I assume there is no issue using a piezo labled "radial mode transducer" in the axial/thickness mode if you can figure out the correct resonant freq of the thickness. How can I figure out the resonant axial frequencey of a piezo disk which is listed as "Radial mode vibration application"? For example:

https://www.steminc.com/PZT/en/piezo-ceramic-disc-10x3mm-r-215-khz

In the following app note:

 https://www.ti.com/lit/an/snaa266a/snaa266a.pdf?ts=1711938847270&ref_url=https%253A%252F%252Fwww.google.com%252F

when reccomending 1MHz transducer the note says "All of the transducers are approximately 2 mm thick. This is due to the requirement of axial (thickness) resonance mode of 1 MHz for these applications". What should the thickness of the disk be for it to be resonant at the following freqs: 40kHz, 200kHz, and 250-280kHz? Can you share how to calculate that so I can find what piezo ceramics will work in axial mode for the freqs I'm looking for?

  • 0
    TI__Mastermind 21940 points

    Hello Pete,

    Thanks for posting to the sensors forum! Sorry you have not had good success obtaining this information from the Steminc website. My recommendation would be to reach out to the transducer manufacturer for better guidance on what transducer you may need as well as the additional support regarding some more specific items regarding their transducers. Some other manufacturers for transducers we have worked with recently are Audiowell, Unictron, and Murata.

    There is a great white paper on the Piezotechnologies website that can help you with the formulas to dentify what thickness you may need. I think they may be in the modes of vibration PDF.

    On another note, TDC1000 I typically recommend using the TDC1000 with frequencies larger than 500kHz. If you are in need of another device recommendation for the frequencies you mentioned above my recommendation would be to use the TUSS44x0 line of devices. I hope this helps!

    Best,

    Isaac

  • 0 in reply to Isaac Lara
    Prodigy 230 points

    Thanks Isaac! Appreciate the reply, that was very helpful. I have a battery application for object/precense detection using a trasnducer in the 450kHz -1Mhz range for detection distance up th up to ~10ft and am considering using the the TUSS4470 or the PGA460. If you have any additional sggestions or comments please let me know. Thanks again.

  • +1 in reply to Pete Sampson
    TI__Mastermind 21940 points

    Hello Pete,

    Thanks for the background on this! The PGA460 is rated from 30-80kHz and 180-480kHz so you may be able to use it for some of your frequencies of interest there and the TUSS4470 is rated from 40kHz-1MHz so it should be able to handle the frequencies you are interested in. 10ft is pretty large for the higher frequencies as they attenuate faster so you have to find the sweet spot of how much resolution you need in the water vs how much distance you can measure with your chosen frequency/voltage combination.

    Best,

    Isaac

  • 0 in reply to Isaac Lara
    Prodigy 230 points

    Thank you! 10ft is the absolute max and will probably switch to lower freqs for thsoe scenerios with higher freqs and detection distance up to 3ft being the norm. Biggest concern is probably battery life