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How to supply a 1mA input and read a mv output proportional to the input current — Parallax Forums

How to supply a 1mA input and read a mv output proportional to the input current

MooneyguyMooneyguy Posts: 77
edited 2011-12-04 05:22 in BASIC Stamp
Is there a way to create a constant 1 ma input to a sensor and then read a mv output that is proportional to the input current? I am wanting to run a pressure sensor and the supplier says the nominal input is 1.0 mA (1.5 ma max) and the output is 0 to 50 mv but it proportional to the input current. I would like to store the input and output data to make decisions for control of another device. I would like to store the last 10 readings in such a way that they will be in memory when the board is disconnected from power and then powered back up again. The schematic of the pressure is located at this website: http://meas-spec.com/downloads/23_33_Std.pdf

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-12-02 22:23
    You can create a constant current source using an LM317L. Look at the National Semiconductor datasheet for this device to learn how it's done. The LM317L is only rated down to 5 mA.

    -Phil
  • $WMc%$WMc% Posts: 1,884
    edited 2011-12-02 23:02
    Take a look at the DS2760.
    '
    Its set-up to read T/C but with some hardware mod's it should do what you need.
    '
    http://www.mouser.com/Search/Refine.aspx?Keyword=ds2760
    BPE
    BPE
    DS2760TC_Demo.BPE
    8K
  • stamptrolstamptrol Posts: 1,731
    edited 2011-12-04 05:22
    The pressure transducer provides an output proportional to pressure, not current.

    What the manufacturer is telling you is that a varying input to the measuring bridge will affect the output. As long as it is relatively stable, your output will vary correctly with pressure.

    There should be some sample circuits available from the manufacturer.

    Cheers,
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