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INA333 Output Decay

Simon Attard
Intellectual 775 points
Other Parts Discussed in Thread: INA333

Hi all,

We are using an INA333 instrumentation amplifier to couple a pressure sensor to an ADC. Below please find attached the circuit of the diagram we are using.

The problem with this circuit is that when the output of the pressure sensor is constant, the output of the IA circuit is seen to decay slowly.

What is the reason for this?

 

Thanks in advance.

Simon

  • 0
    TI__Mastermind 25865 points

    Hello Simon,

    Thank you for the schematic.  We have some additional questions:

    a)  Can you please provide screen captures of this behavior?

    b)  Have you observed the behavior of the reference pin during this decay?

    c)  Can you replace the pressure sensor with a known fixed voltage to ensure that the inputs are not changing?  

    d)  It appears as though you're using a potentiometer to set the reference voltage, correct?  Have you tried replacing the reference circuitry with a bench supply?

  • 0 in reply to Pete%20Semig
    Intellectual 775 points

    Hi Pete,

    Thanks for your reply. I did some additional measurements so that I could answer your questions. Below find a screen shot of the decaying output of the Instrumentation Amplifier.

     

    This graph shows the output of the IA when the input was a step. I did additional measurements to ensure that the input was constant and that the reference voltage was constant as well. I can confirm that.

    I did not try to set the reference voltage using a bench supply, but as I said before, I did some measurements to ensure that the reference voltage is completely stable.

     

    It seems to me that there is some overshot in the IA output, before settling to a constant value. What do you think? Can I modify the circuit in some way to minimize this?

     

    Thanks once again.

     

    Simon 

  • 0 in reply to Simon Attard
    TI__Mastermind 25865 points

    Hello Simon,

    Thanks for the scope shot.

    Can you please provide a scope shot of the input as well? That will help us eliminate any drifting from the bridge. Also, what is the scale of the x-axis in your plot?