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How can I test ultrasonic transducers

Discussion in 'General Electronics Discussion' started by julio_w, Apr 10, 2013.

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  1. julio_w


    Apr 10, 2013
    Hi All,

    I am trying to build a large ultrasonic cleaning bath, I already bought 50 PZT transducers 60 Watts and 40 Khz each from a supplier on china, and I am going to buy a 3 Kw ultrasonic generator to connect all transducers in parallel.

    So before buying the large generator I wanted to test the transducers one by one just to be sure that what i get is what i order, so I decided to buy from ebay one small ultrasonic cleaner of 50 Watts 40 Khz and then I was thinking in replacing the transducer with the new ones one by one and test.

    So my question is how do I test? I know you can do the foil test but that will just tell me that there is ultrasound going on but I want to know the actual frequency of the transducer. So can I just buy a transducer receiver that cost around 2$ and connect at the terminals an oscilloscope? not even sure if that is possible.

    Thanks for reading and I would appreciate your help.
  2. Raven Luni

    Raven Luni

    Oct 15, 2011
    Piezo transducers pretty much only have one resonant frequency (or a narrow band). Any frequencies outside that band will be very weak (if detectable). Your 50W test unit will produce only the frequency it is designed to. So a test will give you 3 possible results:
    - The transducer works
    - The transducer does not work
    - The transducer has a different resonant frequency than you expected.
  3. julio_w


    Apr 10, 2013

    Great, that is what i wanted to hear... thanks a lot.

    My only concern is that i read on a forum that even if it is the same watts in the test device the transducer is likely to be different to the transducers that I do have and it seems that the voltage required to make a transducer work at its designed frequency varies. Is this right? or I am just over worrying?

  4. john monks

    john monks

    Mar 9, 2012
    Why not simply use one transducer as a transmitter and the other as a receiver and use a function generator at 40 kHz to supply one and verify you get a signal from the other? This way you can see if they at least work.
  5. julio_w


    Apr 10, 2013
    I found this schematic for a bat detector, they claim they can detect up to 100 khz and basically divide the frequency by 16 to get an audible signal...


    So I was thinking that if that is true I could do something similar eliminating the frequency divider, ear plug, etc and if I attach an oscilloscope at the exit of IC2 i should be able to measure the frequency, am i right?
  6. sirch


    Dec 6, 2012
    If you just want to know if any utrasonic is being emitted and you have an oscilloscope then just connect one of the transducers directly to the 'scope and hold it close to the one under test, you should pick something up.
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