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How to use water proof ultrasonic sensors?

Discussion in 'Sensors and Actuators' started by sahan hasitha, Jan 9, 2016.

  1. sahan hasitha

    sahan hasitha

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    0
    Jan 7, 2016
    I brought HC-SR04 ultrasonic distance sensor module and removed the ultrasonic transducer and receiver. I added water proof ultrasonic sensors to the circuit and tested it. When um using water proof ultrasonic transducer and receiver, sensors are not working properly. But if i use normal ultrasonic transducer with water proof ultrasonic receiver or normal ultrasonic receiver with water proof ultrasonic transducer, circuit is working fine. I dont know what is the problem. I need a help from someone who have experience with this. These are the images of ultrasonic module and water proof sensors WP_20160109_006.jpg WP_20160109_002.jpg
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    9,000
    1,790
    Nov 17, 2011
    Have a look at the technical data of all the transmiters and receivers and see whether they match.

    From the pictures it is evident that the waterproof transducers are closed whereas the non-waterproof transducers are open. The closed housing will probably introduce some acoustic loss. The energy of the ultrasound output of the waterproof transmitter will be lower than the open transmitter's. In the same way the sensistivity of the open receiver may be higher than that of the waterproof receiver.
    It may just so happen that the combination of open and closer receiver/transmitter or vice versa still is sensitive enough to deliver a useable signal, but when both components are closed (waterproof), the acoustic budget may be too low, meaning that the combined loss of transmitter and receiver is too much to get a useable signal.

    Unfortunately I couldn't find schematics for this module so I cannot judge whether it is possible to beef up the transmit power or the gain of the amplifier at the receiving end to increase sensitivity of the module when used with waterproof ultrasound components. At least that's what I would look for to get the module working with the new components.
     
    hevans1944 likes this.
  3. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    Please provide the name of the manufacturer and the part or model number of the waterproof ultrasonic transducers. A datasheet would be helpful. Are these waterproof transducers piezo-electric transducers or magnetostrictive transducers? Magnetostrictive requires much more power and a different transmitter circuit, although it may serve okay as a receiver to replace the original non-waterproof transducers. For more information, see this link.
     
  4. Shubham Gupta

    Shubham Gupta

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    Feb 2, 2016
    Have u been able to get any solution?
     
  5. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    You have not told us what the waterproof ultrasonic sensors are: manufacturer's name, model number, datasheet, etc. No solution possible without more information. The non-waterproof sensors are standard crystal transducers used everywhere for distance measurement and intrusion detection in air. It is unlikely your waterproof sensors will work in their place on the circuit board shown in your images.
     
  6. Shubham Gupta

    Shubham Gupta

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    Feb 2, 2016
    I am also having the same problem, I haven't posted the original question but have the same problem...I bought from here, manufacture gave this info

    Model: EU1640BCH Diameter:16MM
    Nominal frequency ( KHz) : 40 KHz
    The emission sound pressure at 10V (0 db = 0.02 mPa) :≥110dB
    The receiving sensitivity at40KHz (0 db = V/ubar) : ≥-75dB
    Electrostatic capacity at1KHz, < 1 V(PF) : 1800±30%
     
  7. hevans1944

    hevans1944 Hop - AC8NS

    4,059
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    Jun 21, 2012
    I looked at the vendor page you linked to, as well as pages for several similar transducers. My conclusion is the "waterproof" transducers are just that: immune to water getting inside and ruining the transducer. IMO these "waterproof" transducers are NOT intended for use under water, they are to be used in air.

    One big problem that no one has addressed is the huge impedance difference between air and water. A transducer designed to couple energy efficiently to air will not do so when immersed in a fluid, be it water, Fluorinert, mineral oil, gasoline, kerosene, or whatever. To get some idea of the problem, compare waving your hand in air versus waving it underwater (say in a bathtub or sink). The difference in resistance to motion is very large. The air-based transducer is a tiny crystal that vibrates with a very small displacement, but it is just pushing air around. If you try to push water around, the crystal will not be resonant at an ultrasonic frequency anymore. If it were to happen to resonate at some other frequency, how much power would be required to get the same output in water as it produced in air? Immersed in water, there would be some cooling effect, but is it enough to prevent damaging the crystal? I think not. Probably what you need is a magnetostrictive ultrasonic transducer, of a kind similar to what doctors use for ultrasonic scans of human internal tissue.

    So go ahead and "play" with the "waterproof" transducer. Solder some insulated wires to it and pot the connections in RTV cement. Wait at least 24 hours for the RTV to set up and out-gas. Then hook it up to the original driver board and see what happens when you dip the transducer in water. An oscilloscope helps to see what is going on. I am not a gambler, but if I were, I would bet it quits oscillating when immersed in water. Please let us know what happens as your mileage (or kilometers) may differ.
     
  8. Lance

    Lance

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    Sep 7, 2016
    I am also looking for a waterproof version of the HC-SR04. It is for measuring a water level in a tank. Its range is 50-900mm. The sensor would not be in contact with the liquid but it may be splashed from time to time and subjected to high humidity continuously. It would seem changing out the transducers would be a good solution, Has anyone found waterproof transducers compatible with the HC-SR04's electronics? I've also heard people covering the standard transducers with "cling wrap" to splash-proof them. It doesn't sound very robust, and it would probably change the response and range, however if repeatable may be acceptable. I'd be interested in hearing of anyone's experience with that.
     
  9. shrtrnd

    shrtrnd

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    450
    Jan 15, 2010
    Boy. Somebody is going to get upset about this. Another hijacked post
    Having been beat-up over this type of thing, I'll mention that we're supposed to start a new post with our own
    questions on this forum.
    I know most other websites, people just jump-in with their own requests, but here, the moderators prefer it if
    you open your own post with your own question, so that sahan's original question doesn't get lost in the shuffle.
    Just an observation.
     
  10. ritesht

    ritesht

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    Jan 6, 2019
    Sorry for bumping up an old thread but I was in the same boat of requirement.

    Then to my surprise I found out there is a new sensor

    https://www.ebay.com/itm/253978673298

    It has 2 transducers instead of 1 so it has smaller minimum detection distance as compared to JSN SR04T.

    Also its main board is not exposed like the JSN SR04T since it looks properly sealed and is therefore fully waterproof.
     
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