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(wheatstone bridge) Pressure stimulation

Discussion in 'General Electronics Discussion' started by ykho21, Feb 4, 2012.

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  1. ykho21

    ykho21

    3
    0
    Feb 4, 2012
    Good day,

    I'm a new member here. I am planning to make a small project which used to stimulate the pressure without the pressure gauge. This is a wheatstone bridge gauge with 1Kohm resistance each leg. Please refer to the picture.

    How can I built a circuit that have a mV output? The Ex in is 5V.
     

    Attached Files:

  2. Harald Kapp

    Harald Kapp Moderator Moderator

    10,327
    2,243
    Nov 17, 2011
    VB = Vex* (Rb/(Ra+RB) -Rx/(Rx+Rc))

    So by carefully chosing the Rs, almost any output voltage from 0 to Vex can be generated. A rather simple Choice is:
    Ra = Rc
    Rb = Mean(Rx)
    with
    Mean(Rx) = the mean value of the variable resistor = (Rxmax-Rxmin)/2
    The output voltage results from the imbalance of the resistive dividers. So by more or less balancing/unbalancing the rresistor ratios you can set the voltage.

    Harald
     
  3. ykho21

    ykho21

    3
    0
    Feb 4, 2012
    Harald,

    Thanks for your reply. RB=Rb? Today i just make an experiment to put in a single 1.5K variable resistor on this Rx. Since the change of resistance is high and affect the pressure reading (mV/V) output, I decided to put 1K resistor in series with 10 turn 100ohm variable resistor in Rx to make resistance change more precise. Means, Ra=1K, Rb=1K, Rc=1K and Rx=1K+100ohm 10 turn variable resistor. From this I can get the 1mV output. Is it alright to have a circuit built like this?
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

    10,327
    2,243
    Nov 17, 2011
    Yes,
    that's o.k.

    Harald
     
  5. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    Here's a way to make an adjustment even more precise.
    You change the values depending on the resistors you have access to and the adjustment range you want.
     

    Attached Files:

  6. ykho21

    ykho21

    3
    0
    Feb 4, 2012
    Hi,

    Thanks for all for the comment and help. WIll try out both method to solve the problem.
     
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