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Bubble level detection using FDC2214

ttd
Mastermind 8350 points
Other Parts Discussed in Thread: FDC2214

Dear Technical Support Team,

I have a question about FDC2214. I'd like to try to detect Bubble(not soapy water) using FDC2214 EVM

and refer following application report.

www.tij.co.jp/.../snoa935a.pdf

Is it for just soapy water? I'd like to detect bubble level (it's not liquid), especially situation which it's level decreases as time proceeds.

I have been preparing container attached sensor.

Best Regards,

y.i

  • 0
    TI__Expert 7400 points

    Hi:

     It is not feasible to detect just the bubbles of soap water because you cannot distinguish between the soap water itself compared to the bubbles itself.

    Thanks

    -David Wang

    Capacitive Sensing Applications

  • 0 in reply to David Wang11
    Mastermind 8350 points

    Hi David,

    Thank you for your reply.

    I'm sorry that my  explanation may be not enough. I'd like to detect only bubble level.

    Please show following picture. I have been trying it.

    The container includes only bubble. It doesn't includes a liquid such as soapy water. 

    Best Regards,

    y.i

  • 0 in reply to ttd
    TI__Expert 7400 points
    Thanks for the clarification. It should be possible. The concern will be the sensitivity that you need out of the system. The bubbles only case will have a lot of air mixed in, so the density of the target will be very small. This ultimately makes the change in capacitance much smaller since the dielectric constant and density will not be very different compared to air. Another issue will be the uniformity along the z-axis, as you fill up, over time, you may see that the level will go down at a fixed level since the bubbles may be reduced.

    What are you seeing in terms of capacitance changes?

    Thanks
    -David Wang
    Capacitive Sensing Application
  • 0 in reply to David Wang11
    Mastermind 8350 points
    Hi David,

    Thank you for your reply.

    I will try small rage capacitance detection for bubble. I think that I should change the range of GUI.
    My customer expects to see the bubble level will go down as time proceeds with FDC.
    Their requirement precision of bubble level is 1mm.
    For Example.

    Now : 10mm
    After 1hour: 9mm
    After 2hours: 8mm
    After 3hours: 7mm
    ・
    ・
    ・

    Best Regards,
    y.i
  • 0 in reply to ttd
    TI__Expert 7400 points
    that resolution will be very hard to achieve depending on how large the sensors are but also the density of the bubbles. If the bubbles contain much more air (low density), then your sensitivity will be significantly smaller than expected.

    Thanks
    -David Wang
    Capacitive Sensing Applications
  • 0 in reply to David Wang11
    Mastermind 8350 points

    Hi David,

    I have been trying to detect the bubble level with FDC2214.

    It causes the decreasing the capacitance value at first.

    Second , the capacitance value is increasing slowly.

    Maybe I think that air of bubble is increasing during popping bubbles.

    But I don't know why the capacitance value decreases.

    How do you think about it? Following the GUI of FDC2214.

    I think that it is difficult to detect same capacitance value depending on the bubble level anytime anywhere for bubble level.

     

    I can get the increasing capacitance value if I pour a water into the container.

    Best Regards,

    y.i

  • 0 in reply to ttd
    TI__Expert 7400 points

    I would have to see the setup and the testing running. I would expect that it may be in your setup but also in how the bubbles are "poured" into the container. The decrease in capacitance is probably due to the increase in air density compared to soap density.

    Thanks

    -David Wang

    Capacitive Sensing Applications