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The ramifications of fuel level sensing — Parallax Forums

The ramifications of fuel level sensing

James LongJames Long Posts: 1,181
edited 2007-01-22 19:21 in General Discussion
Ok....so I want to sense the fuel level in a tank.....

I would like suggestions to thoughts on how to do it accurately and safely.

The fuel is gasoline,·I don't want to instigate a flaming ball of destruction.

Ideas and thoughts????

James L

Comments

  • Robert KubichekRobert Kubichek Posts: 343
    edited 2007-01-21 20:59
    James Long said...
    Ok....so I want to sense the fuel level in a tank.....


    I would like suggestions to thoughts on how to do it accurately and safely.



    The fuel is gasoline, I don't want to instigate a flaming ball of destruction.



    Ideas and thoughts????



    James L

    Put some reed switches in a rigid plastic tube and inject the tube with silicon rubber,
    then make a float that slides on the tube with a magnet on it.
    The # of reed switches you use will determin the accuracy you get....

    Bob scool.gif
  • James LongJames Long Posts: 1,181
    edited 2007-01-21 21:03
    Bob,

    Not a bad idea....but silicon and gasoline do not mix. The silicon will degrade quickly....and end up in the fuel line.

    Thanks for the idea....but I would like an easier approach.

    James L
  • UnsoundcodeUnsoundcode Posts: 1,532
    edited 2007-01-21 21:19
    Hi James, I believe car manufacturers use a float that operates a potentiometer. As far as the electrical supply it should be either outside the proximity of any flammable material that may escape or in an·enclosure that prevents ingress of flammable gases, cools the heat to a safe level from any kind of explosion inside the enclosure or the supply should be intrinsically safe (current limited to where a spark can not occur). I would guess the equipment would have to be UL listed or something like that to prevent prosecution after the flaming ball of destruction tongue.gif .

    Jeff T.
  • Robert KubichekRobert Kubichek Posts: 343
    edited 2007-01-21 21:22
    Then use a different potting compund, and a tube material that is gas impervious...
    A teflon/nylon tube would work,and gasket compound would work to pot the reed switches.
    Even a brass or stainless tube would work if the magnet was strong enough.

    Bob
  • James LongJames Long Posts: 1,181
    edited 2007-01-21 21:37
    Would it be possible to use a capacitance system to read the fuel level, or would this possibly introduce a spark??

    James L
  • UnsoundcodeUnsoundcode Posts: 1,532
    edited 2007-01-21 21:48
    Anything requiring electricity can produce a spark unless the voltage and current is limited. Some intrinsic systems use a zener/resistor combination to limit the current and voltage. It would be interesting to know how it's done in a car because the pot sits right on top of the tank.

    Jeff T.



    EDIT
    I have to relate this story, two guys at a place I worked were cleaning an open top vessel that used acetone as part of the process, they both got badly burnt when a static discharge from one guys clothes cause an explosion. Fortunately they both survived but after that our company went ground strap crazy.

    Post Edited (Unsoundcode) : 1/21/2007 9:54:38 PM GMT
  • James LongJames Long Posts: 1,181
    edited 2007-01-21 21:56
    Jeff,

    The reason I ask this. I know there are capacitance systems out there. I worked on an aircraft that used capacitance probes to read the fuel level. I know you can buy capacitance probes for you car's fuel tank.


    I would think.....the most important part of the equation......make sure they are always wetted, and ensure the current and voltage is restricted as well.

    James L
  • UnsoundcodeUnsoundcode Posts: 1,532
    edited 2007-01-21 22:06
    Yes James I have used the capacitance probes in flammable material the ones I used had an intrinsic power supply. Your last sentence sums it up. There are tables out there that will tell you how much power is required to produce a spark from that you can design your psu. If you have an intrinsic supply it will open up your options.

    Jeff T.
  • gcarlsongcarlson Posts: 8
    edited 2007-01-21 22:46
    Google/Ebay: Tempo Marine Fuel Sending Unit 6-12" 570ESU
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-01-22 01:27
    James,

    Have you read the information on the website, "How Stuff Works"? Lots of great information there.

    http://auto.howstuffworks.com/fuel-gauge1.htm


    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Chris Savage
    Parallax Tech Support
  • RabidRabbitRabidRabbit Posts: 1
    edited 2007-01-22 12:58
    Try a magnet in a float and a hall effect sensor.
  • James LongJames Long Posts: 1,181
    edited 2007-01-22 19:04
    I'm trying to measure the liquid level......not have a low level indication.

    But I appreciate the help,

    James L
  • UnsoundcodeUnsoundcode Posts: 1,532
    edited 2007-01-22 19:14
    Hi James, looking at the link Chris Savage provided it looks like car tanks rely on the fact the seal is good enough to prevent fuel or fumes escaping, if you think you can seal your tank like that then the link gcarlson provided have the ideal thing if the size is suitable for the tank, you might even be able to visit a wreckers yard and adapt one from an old vehicle. How big is your tank btw.

    Jeff T.
  • James LongJames Long Posts: 1,181
    edited 2007-01-22 19:21
    The tank is 12.5 gallons.

    Neat.

    thanks,

    James L
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