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Fixed pH measuring circuit .

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by Minh Thanh, Sep 24, 2017.

  1. Minh Thanh

    Minh Thanh New Member

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    Can you give me your opinion about this ? Whether I can take a buffer circuit to the second opamp's non-inverting input ? Thank.
     

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  2. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    R1 and C1 form a filter/smoothing circuit for the PH signal.
    Also if you connected the buffer output to the -inp of the 2nd stage, Vout would be inverted.

    Why do you want to change the circuit.?

    E
     
    Last edited: Sep 24, 2017
  3. Minh Thanh

    Minh Thanh New Member

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    What happen if I detach out R1 and C1 the circuit and connecting buffer output to -inp of 2nd stage .?
     
  4. dave

    Dave New Member

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  5. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    If you connect the output of the buffer directly to the -inp of the 2nd stage, the amplifier will work correctly.
    Why do you want to change the circuit.?
    E

    EDIT:
    Look at these two simulations, original and modified.
    Corrected the OPA supply voltages.
     

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    • A10.gif
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    Last edited: Sep 24, 2017
  6. Minh Thanh

    Minh Thanh New Member

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    I mean is to connect the non- inverting input of 2nd stage not inverting input. Reason that I want to change is because I want to own a new circuit for myself . The circuit that I shown which is original circuit on a workshop web. However, If Vout will be inverted , Can I use absolute circuit to make Vout become positive ?
     
    Last edited: Sep 24, 2017

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