Fluid Level Sender

Discussion in 'General Electronics Chat' started by h2opolo, Jun 19, 2014.

  1. h2opolo

    Thread Starter Member

    Aug 2, 2013
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    Does anyone know how a fluid level sender like this works? This particular one uses resistance to indicate fluid level. When the float is higher, there is less resistance in the wires. I found the design interesting. How does it work? What circuitry is involved and how does the float interact with the rod?

    I have one that broke. Can they be fixed? If not, I am still interested in the physics behind it.


    [​IMG]
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,998
    745
    Looks like its a magnet and reed switches in side 240 - 33 ohms,pdf
     
    Last edited: Jun 19, 2014
  3. h2opolo

    Thread Starter Member

    Aug 2, 2013
    38
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    Thanks, I read about reed switches. From what I understand, they open and close due to the force of the magnet. How would that create resistance? Im guessing the float contains a magnet? How would the resistance change?
     
  4. pwdixon

    Member

    Oct 11, 2012
    488
    56
    Perhaps there's a number of reed switches along the rod and a number of different resistors?
     
  5. pwdixon

    Member

    Oct 11, 2012
    488
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    I did find this online:

    [​IMG]
     
  6. h2opolo

    Thread Starter Member

    Aug 2, 2013
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    that seems plausible. I'm thinking that since my multimeter doesn't even show a closed circuit, one of the wires must have corroded or disconnected on the inside.
     
  7. pwdixon

    Member

    Oct 11, 2012
    488
    56
    Mechanical things always wear out eventually, could be a reed failure or probably more likely as you say a wire that's been vibrated and broken so it's most likely outside that actual sensor assembly. It's the same as the dc power plug that goes into your laptop that always breaks at the bend just into the cable at the rear of the dc plug itself.
     
  8. h2opolo

    Thread Starter Member

    Aug 2, 2013
    38
    0
    That makes sense. Thanks for the diagram!
     
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