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Pressure gauge schematic

Discussion in 'Electronic Components' started by Vincent Himpe, Aug 29, 2004.

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  1. I'm looking for a schematic of a pressure gauge that uses a load cell (
    wheatstone bridge )

    Gauge measures between 0 and 4500psi ( 300 bar ) I got the load cell

    problem is signal conditioning. full scale is only 100mV. and i need to
    amplify this to 2.25 volts ( so 0.5 millivolt is 1 psi. the gauge gives me
    )

    The opamp circuits i made all tend to drift and are sensitive to noise due
    to the high gains involved . plus ther eis the problem of the common mode
    voltage.

    I know tere are special instrumentation amps available but those cost an
    arm and a leg. Does anyone have a schematic on how to build this using
    regular god opamps like op177 ?
     
  2. Ross Herbert

    Ross Herbert Guest

    On Sun, 29 Aug 2004 09:13:27 GMT, Vincent Himpe

    |I'm looking for a schematic of a pressure gauge that uses a load cell (
    |wheatstone bridge )
    |
    |Gauge measures between 0 and 4500psi ( 300 bar ) I got the load cell
    |
    |problem is signal conditioning. full scale is only 100mV. and i need to
    |amplify this to 2.25 volts ( so 0.5 millivolt is 1 psi. the gauge gives me
    |)
    |
    |The opamp circuits i made all tend to drift and are sensitive to noise due
    |to the high gains involved . plus ther eis the problem of the common mode
    |voltage.
    |
    |I know tere are special instrumentation amps available but those cost an
    |arm and a leg. Does anyone have a schematic on how to build this using
    |regular god opamps like op177 ?
    |


    Possibly something like http://www.linear.com/pdf/lt1250.pdf
     
  3. Looks like what i need.
    Except i dont have negative voltages and the gain resistor is not prsent
    either. I'll feed the top and bottom of the bridge 2 known 'hard' reference
    voltages ( coming from my A/D system ).

    Output of the opamp goes to a 12 bit a/d convertor. Scaling and offset
    happens in the cpu. I checked prices. Seems acceptable: 6$, drops to 3$ per
    1000. and readily available.

    Thanks. I see you responded to the oxygen thing too. Unfortunately they
    won't sell to me. But i found a company that sells these things to
    individuals.
     
  4. Making your own dive computer? Make sure you sign off on all the
    "life support" documentation from each and every one of your
    vendors...
     
  5. William P.N. Smith wrote in 4ax.com:
    nope. fully automatic nitrox/trimix blender and analysers
     
  6. Yow! More power to you, but make sure your {business,life} insurance
    is well paid up, and for a couple of orders of magnitude more than you
    think you need! 8*}
     
  7. Ross Herbert

    Ross Herbert Guest

    On Sun, 29 Aug 2004 12:52:02 GMT, Vincent Himpe

    ||
    |> On Sun, 29 Aug 2004 09:13:27 GMT, Vincent Himpe
    |>
    |>|I'm looking for a schematic of a pressure gauge that uses a load cell
    |>|( wheatstone bridge )
    |>|
    |>|Gauge measures between 0 and 4500psi ( 300 bar ) I got the load cell
    |>|
    |>|problem is signal conditioning. full scale is only 100mV. and i need
    |>|to amplify this to 2.25 volts ( so 0.5 millivolt is 1 psi. the gauge
    |>|gives me )
    |>|
    |>|The opamp circuits i made all tend to drift and are sensitive to noise
    |>|due to the high gains involved . plus ther eis the problem of the
    |>|common mode voltage.
    |>|
    |>|I know tere are special instrumentation amps available but those cost
    |>|an arm and a leg. Does anyone have a schematic on how to build this
    |>|using regular god opamps like op177 ?
    |>|
    |>
    |>
    |> Possibly something like http://www.linear.com/pdf/lt1250.pdf
    |>
    |>
    |
    |Looks like what i need.
    |Except i dont have negative voltages

    You can generate your own negative voltage from the positive supply
    using an inverter. eg.
    http://www.linear.com/prod/datasheet.html?datasheet=179

    |
    |
    |Thanks. I see you responded to the oxygen thing too. Unfortunately they
    |won't sell to me. But i found a company that sells these things to
    |individuals.

    Wouldn't the companies concerned let you know who their distributors
    were in your area? Anyway, it is fgood to see you found a source.
     
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