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Water Depth Pressure Sensor?!?!

Discussion in 'Electronic Basics' started by Dan T, Jan 6, 2004.

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  1. Dan T

    Dan T Guest

    Hi all, I'm planning on measuring the depth of water using some form of
    pressure sensing. Does anyone out there know of any pressure sensitive
    resistors that would be suitable for this, that aren't too expensive? All
    the ones I find on the net are pretty OTT for what I'm trying to do.

  2. Dan T

    Dan T Guest

    .....or even better a device that can give a varing output voltage depending
    on pressure.
  3. Digikey lists 760 different pressure sensing transducers, some of them
    quite inexpensive. How deep do you need to measure?
  4. you didn't mention how deep..
    a couple of simple things..
    washing machine water level sensors have a limited range and are cheap and
    a toilet float with a pot on an arm would work..
    hank wd5jfr
  5. Dan T

    Dan T Guest

    not deep.....0 - 1 meter would be more than enough.
  6. Is the water inside a vessel, or exposed to atmosphere? Can you run
    an air tube from above the water to the sensor, to give a surface
    pressure reference? Remember each 2.2 feet depth of water accumulates
    about 1 psi of pressure, so you need a transducer that has a full
    scale pressure range of at least 1.5 psi.

    Here is a 0-2 psid (pounds per square inch differential) device: Specialties Inc/Web Data/Model 1210.pdf

    sold by Digikey for under $30 that could be potted and submersed with
    an air tube run to above the surface connected to one port, and the
    other port open to the water. Of it could be outside a tank, at the
    level of the bottom of the tank, with one port connected to the water,
    and one vented to air. That would measure the height of the surface
    above the transducer.
  7. Rileyesi

    Rileyesi Guest

    Remember each 2.2 feet depth of water accumulates

    Can you give me a reference for this type of information? I need to find out
    the change in pressure per depth for salt water and fresh water at different

    Thanks loads (if you'll pardon the pun!).

  8. John Fields

    John Fields Guest

    Different John, but here's a link for pure water:

    Salt water's a little tougher since density varies with salinity _and_
    temperature, but here's a great link with a calculator! Water Equation of State Calculator.htm
  9. erehwon

    erehwon Guest

    Here's what I'm using for pretty much the same thing (ie. same depths):
    Motorola's MPX5100DP

    It cost me £10 from Arrow Electronics


    Covers pure water, but not salt water.
  11. Dan T

    Dan T Guest

    thanks for the replys guys, ...stupid question do you put one
    of these devices actuatly in water????
  12. erehwon

    erehwon Guest

    Just to give you some idea: The 'package' in my case is a small plastic case
    with metal connectors for the electronics side of things, and has a couple
    of 'push-on' connectors for the pressure connector. So you just push some
    small tubing on and take that to the place you're measuring from. (You
    probably want to give the tube a few large turns so that you don't
    accidently get any water up it into the sensor.)
    My tubing is from the local Aquarium and fits okayish.

    Out of curiosity - can I ask what you're making?

  13. Dan T

    Dan T Guest

    for part of my training for work i've got to come up with some electronic
    system of measuring how much fuel is in a aircrafts fuel tank (not real,
    just imaginary)......and have it shown on a display. Its all for a
    competition. Once i've got a output thats proportional the the liquid level
    i'm fine. We can't use floads, or arms adjusting a pot, or do anything that
    involves direct contact with current and fuel.

    thanks for ur help everyone,
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