ultra sound principle to measure depth

Discussion in 'The Projects Forum' started by wilbertrk, Jun 8, 2010.

  1. wilbertrk

    Thread Starter New Member

    Jun 4, 2010
    Let me explain my need,in laboratory model the depth of water is 50cm and this water depth is constant through out the experiment,below this water the depth of sand will vary with time due to some effect being created, I am to measure the depth of sand below water, while making measurement the water is without motion and there is no turbidity. Can I use the ultra sound principle to measure this sand depth below water, Kindly help me with information and ideas
  2. kubeek


    Sep 20, 2005
    Ultrasound could be quite difficult to implement, because you will need some fairly advanced way to process the data, assuming you want good precison, like +/- 1cm depth for a 1cm2 big spot.
    You could try to use some ready made laser distance meter that can measure that close, and test it if it could do its measuring underwater, and how accurate.
  3. coldpenguin

    Active Member

    Apr 18, 2010
    I am assuming that the sand is going to be sedimented from the water? I am wondering whether there would be enough of a boundary for ultrasound to work (otherwise it is going to be a spongey kind of response).
    But then I am thinking that if it is sand sedimenting out of water, that a laser would also have issues with the muddy water.

    Could you perhaps put a small strain guage under the water, in the area you require to measure? (you are talking lab here and not a boat going down a river?).
  4. jpanhalt


    Jan 18, 2008
    Get a FatMax (Stanley) laser distance measurer. They are quite accurate and can be had for good prices, if you shop around. Mine was $50 new in box on ebay. They work by time of flight (TOF).

    Water is transparent to the wavelength of light used, but of course, because light is slower in water than in air, your initial reading may seem a little off. However, since the depth of water is constant, that won't really matter. If the water depth changes, then a calibration curve will solve that problem too.

    One neat thing about the laser is that you can see exactly the point that is being measured. That is not the case with ultrasound, as the beam can be quite wide. If you want multiple, automated measurements, you will need to do a little hacking. But, I suspect that little bit of hacking will be a lot easier than developing a TOF laser instrument from scratch.