Help with data acquisition project

Discussion in 'The Projects Forum' started by kjmason, Jan 15, 2013.

  1. kjmason

    Thread Starter New Member

    Jan 15, 2013
    2
    0
    Hello,

    I am working on a data acquisition system that uses a panel pc, an amplifier circuit and an off the shelf data acquisition module. Ever since I introduced the amplifier to the circuit I find that my signal from the amplifier to the analog input increases and decreases when I open and close the door of the enclosure. I can't find anything that jumps out at me as being a problem. Can anyone offer any suggestions?
     
  2. tracecom

    AAC Fanatic!

    Apr 16, 2010
    3,869
    1,393
    Temperature change which affects the amplifier?
     
  3. crutschow

    Expert

    Mar 14, 2008
    13,002
    3,232
    What are you measuring? Is the amplifier input open? What is the amp gain? What is the magnitude of the change?
     
  4. kjmason

    Thread Starter New Member

    Jan 15, 2013
    2
    0
    I don't think it is temperature because it happens almost immediately where a temperature increase takes some time.

    I am measuring mV from a strain gage. My full scale input is 20mV. I am gaining the signal just about 5 times. The magnitude of change is about 20μV which is enough to change my reading. I'm just trying to get to the bottom of what could cause this. My readings aren't noisy. There is just a shift when the door is opened or closed.
     
  5. crutschow

    Expert

    Mar 14, 2008
    13,002
    3,232
    Perhaps the strain gage is sensitive to small atmospheric pressure changes or the sound of the door. Is is just a blip or is it a shift? Is the voltage change in the same direction when the door is opened and then closed?
     
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