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Measure tide / swell

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by stuee, Sep 21, 2017.

  1. stuee

    stuee Member

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    Hi,
    I want to make something to measure swell and tides. Im messing with Raspberry pi 3 and have other sensors working but not sure how to do this one.

    The tides mainly go from .0.3m to 4.5m and swell -2m > +2m

    I was thinking of a floating sealed ball with an altimeter inside and also temp probe out the bottom a little.

    After reading up how altimeters work is on pressure but if its inside a sealed ball would it not work properly, even when it gets warm and may increase the ball pressure a bit.

    Am i thinking correct and if so what can it do or anything else i can try?

    thanks for your help.
     
  2. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    Tides are usually measured with submerged pressure sensors connected to electronics using a cable with an air tube., swell can also be measured in the same way.

    E
    What is your location.
     
  3. stuee

    stuee Member

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    so you mean a ball for example, that has a long breather tube that also contains the cable too?
     
  4. dave

    Dave New Member

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  5. dr pepper

    dr pepper Well-Known Member Most Helpful Member

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    If you can get an accurate enough gps receiver you might be able to do it measuring altitude.
     
  6. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    The sensor is a thin metal diaphragm, one face is exposed to the sea water and the other face exposed to the surface air pressure by means of the air tube.
    It is a differential sensor, which compensates for the ambient air pressure which effects the tide/water height.

    The sensor sensor is suspended in the water at a depth below the lowest expected level.
    In the UK we used sensors 1Bar upto 2.5Bar [ ~ 10mtrs to 25mtrs]

    E
     
  7. stuee

    stuee Member

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    dr pepper, would it work ok inside a sealed ball? can i add external antennas?
     
  8. Musicmanager

    Musicmanager Active Member

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  9. atferrari

    atferrari Well-Known Member

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    Hola Eric,

    IIRC that was the system used in a vessel to get continuous draft readings even when underway.

    How do you get the average value to catter for swell?
     
  10. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hola,
    For swell we used 3 axis Heave compensation onboard the Survey/Dredging vessel and applied correction to the water depth measured by the echo sounder in order to get a 'true' depth.

    For a quay wall fixed tidal sensor we used tide height averaging .

    In some underwater pipe laying projects we had to measure wave heights.

    Eric
     
  11. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    One of the downside of capacitance and resistive sensors was the build up of algae and other crud on the face of the sensors.

    A simple fixed height sensor can be made with a ultrasonic surface sounder located inside a stilling tube/well [ a bit of plastic drain pipe works OK].
    Using a piece of pipe, a float/counter weight with a cord turning a potentiometer was used in the olden days
    E
     
  12. Musicmanager

    Musicmanager Active Member

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    Hi Eric .. .. .

    Yes, I've been reading about the issues and problems caused by build up of algae and the like. I've also read a bit about an ultrasonic solution. For my own purposes I'm actually looking for the means to assess the contents of a fairly modest tank that holds clean water, which is drained and replenished regularly.

    I've had a play with capacitive probes with some fairly indifferent results so far, but I'm waiting on the arrival of some bits & pieces to make a more proficient probe. I've also got some ultrasonics on order, but there seems to be an issue with condensation moisture causing circuit failure. There is a solution but it is very expensive.

    I wouldn't suggest that the article I appended will offer any solution, but it is a good place to start when discovering the pitfalls.

    S
     
  13. dr pepper

    dr pepper Well-Known Member Most Helpful Member

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    Yes so long as the plastic doesnt contain metal, some abs does.
     

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