Instrument amplifier

Discussion in 'Homework Help' started by odinhg, Sep 16, 2009.

  1. odinhg

    Thread Starter Active Member

    Jul 22, 2009
    65
    15
    Hi!

    I'm not very good at op amp circuit design, so I was hoping somebody could point me in the right direction.

    What I need to do is to get a "readable" signal (0-5V/0-10, not very important, it just have to be on the Volt scale, not mVolts), from a absolute pressure sensor which give me 100-0 mV / 0-100 psi if I've got it right. The sensor is a SDX100A2 (datasheet).

    I'm not expecting a complete solution to my problem, but a pointer to some good resources, amplifier tips and other suggestions/answers is greatly appreciated!

    Thanks in advance, odinhg :)
     
    Last edited: Sep 16, 2009
  2. JDT

    Well-Known Member

    Feb 12, 2009
    658
    85
    The best way is to construct an instrumentation amplifier out of three op-amps.

    See http://en.wikipedia.org/wiki/Instrumentation_amplifier

    The inputs come from the + and - outputs on your sensor. Configure the gain of the instrumentation amplifier to get the output voltage swing you need.

    John
     
  3. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    You will probably not achieve the best performance with an instrumentation amplifier you build from three op-amps. You can buy off-the-shelf purpose built instrumentation amplifiers - such as the INA114.
    What you pay in extra dollars is offset by the significantly shorter time required for construction and lack of stress in getting the design working. Such devices are easily configured for the desired gain and provide excellent performance with modest attention to good design & layout.
    Consult a manufacturer's data sheet (pdf downloads are normally readily available) for important design information and examples.
     
  4. Ratch

    New Member

    Mar 20, 2007
    1,068
    3
    odinhg,

    OP amp circuit design is best left to the professionals who usually work together as a team. It involves several specialities such as semiconductor die fabricating, and microcircuit design techniques. It is an advanced skill that needs years of study and experience, along with a large investment of expensive equipment and startup costs. Unless you have deep pockets and the resources of a electronics manufacturing company, I would suggest you stick with what you can buy off the shelf and use them to design applications.

    Ratch
     
  5. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Pedantry in action, I think.:D
    I believe he meant that he is not good at designing circuits which include op amps.
    Or perhaps you were mocking him, knowing what he really meant.
     
  6. odinhg

    Thread Starter Active Member

    Jul 22, 2009
    65
    15
    Hehe, that's correct. My english isn't that good unfortunately.

    JDT and t_n_k, thanks! I think I'll go for an instrumentation specific amplifier.

    Thanks again :)
     
  7. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    If you built an instrumentation amplifier out of discrete components you will not achieve the performance of an IC instrumentation amplifier because the components are not closely matched like in an IC. A single supply instrumentation amplifier, powered by 12V, can give you a range of 0-10V if its gain is 100.
     
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