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Design Challenge: Measuring liquid inside a closed container

Catwell
We have some liquid inside a canister, any size. The challenge is to measure the liquid level inside from zero to 100 percent. However, there are some rules:

1. Can not place any type of device inside the canister
2. Nothing can be placed where the enclosure is filled or drained
3. Can not alter the overall canister shape, size, orientation

My original idea is ultrasonic bounceback from the top of the cylinder. But not knowing the container thickness, will the ultrasonic waves propagate at all?
 
Any ideas? There is no right or wrong answer.

Cabe
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  • I don't know what kind of liquid, that you need to measure. But my sugestion is as follows

     

    • Use some kind of Magnetic resonance imaging
    • Just measure the change in weight

     

    The description you are giving is a bit unclear,  so are more precise answer is hard to give.

    I would like to know the following

     

    • max and min size of container ?
    • what kinds of liquids ?
    • what will the sides of the container be made of?
    • A what rate will the liquid level change (min/max)?
  • in reply to Former Member

    To elaborate on the problem:

     

    - Min/Max size of the container : 1m Diameter 1m Tall / 10m Diameter 10m Tall (To make it easy, I am making it a cylinder)

    - Type of liquid : Any & Possibly pressurized gas (propane, co2, etc)

    - Container material : Steel

    - Liquid Level changes : Once a day


    - Weight is not measurable.

     

     

    I believe this is solvable since liquid flow rate in a pipe is measurable from the outside, why not liquid level.

     

     

    I like the idea of measuring capacitance!

     

    Cabe

  • in reply to Catwell

    Well capacitance won't work with a steel container!

     

    One plausible way to get ultrasound to work would probably be to mount a transducer on the bottom of the tank, and see if you can detect the reflection off the surface of the liquid.  The air to steel acoustic impedance mismatch would probably rule out a top mounted system.

     

    Another would be mount the transducer on a track along the side of the tank, then you'd run the transducer up and down the tank.  I would venture you'd see a measurable increase in reflection amplitude as it moved from liquid to no liquid.  The solution would be very ecxpensive though, not only would you need moving parts, but you'd need to use special goo between the transducer and the wall of the tank to ensure no air gaps.

  • in reply to Catwell

    Since it is a steel container  ----  hit it with something hard & it will ring, the frequency &/or form of the resultant ring will tell how full it is.

     

    R

  • in reply to Former Member

    Roger,

     

    I like your idea. Measuring the results after tapping the enclosure. Outside noise might be an issue though.

     

    Cabe

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