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voltage scaling

Discussion in 'Electronic Basics' started by [email protected], Nov 2, 2006.

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  1. Guest

    I am using an analog sensor and would like to scale the output voltage
    down prior to recording the value. I am running into problems
    acheiving this, however. I have tried a simple voltage divider circuit
    but the current from the sensor output is so minute it does not
    function properly. Does anyone have any suggestions on how to scale
    voltage with very little current? Thank you,

    Evan
     
  2. Without all the details, a design isn't possible. But an opamp is a
    very common approach to this.

    Jon
     
  3. Baron

    Baron Guest

    If the resistance of your voltage divider dragging too much current then
    raise it ! Try a value 10 times higher !
     
  4. Problem is, we don't know what the OP is hooking up to the divider to
    monitor the voltage and how it loads it.

    Jon
     
  5. Baron

    Baron Guest

    Thats why I suggested it that way ! Don't 10M DMM's come in handy !
     
  6. Skeptic

    Skeptic Guest

    The more details you provide the better the answers you will receive. What
    is the voltage and current the sensor provides. Better yet, what is the
    sensor and what is it measuring?
     
  7. If this is a pH sensor, say, you need to design the input circuit correctly.



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  8. Guest

    The sensor is a MEMS biaxial accelerometer I am using to measure tilt.
    I am suppling 3V, the output voltage range is 1.25 V +/- 0.1 V and the
    current is less than 0.01 mV (I calculated it to be aprox 0.005 mV).
    Thanks
     
  9. redbelly

    redbelly Guest

    Current is measured in mA, not mV. Please clarify, are you talking
    about the output voltage or current? Also, what resistance did you use
    for the voltage divider?

    Mark
     
  10. Guest

    Output voltage: 1.25 V
    output current: .005 mA

    I used a 150 and 220 kOhm resistors.
     
  11. redbelly

    redbelly Guest

    their output is essentially a voltage source. The output current just
    depends on what resistance is tied to the output.

    I don't know what you're using to read the signal. If you're looking
    at the output on an oscilloscope, that's typically a 1 M-ohm load and
    that will alter the reading on a several-hundred kOhm divider. On the
    other hand, a 10 M-ohm multimeter should have very little affect on the
    reading.

    I would try making a divider in the 10-20 kOhm range, and see if things
    work better. Alternatively, if you're up to putting together an op-amp
    circuit, that would work best of all.

    Mark
     
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