Eliminating Background Noise using Labview

Hello,
I have built a VI that is used to measure voltage from an amplifier connected to a photomultiplier tube.  The PMT reads a fluorescent light signal and sends it to the amplifier, which converts current to voltage.  I get a pretty decent signal reading, but I want to cut down the background noise that shows up.  For some reason, the background noise starts around 1.5V and randomly oscillates between 1.42 volts and 1.54V.  I am trying to find a way to cut down the noise so my readings are a little more clean.  I have attached my VI and a picture of the resulting graphs I get from a typical data run.  The left graph shows background noise in a 4second interval, and the right graph shows the complete run. 
Any help, suggestions or comments is very much appreciated.  Thank you!
Attachments:
AOAI Data Aquisition copy.vi ‏40 KB

Looks pretty clean to me.  Just curious, why do you need it to look cleaner than that?
Bill
(Mid-Level minion.)
My support system ensures that I don't look totally incompetent.
Proud to say that I've progressed beyond knowing just enough to be dangerous. I now know enough to know that I have no clue about anything at all.

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