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DC bias with ground input affecting math integrate function

Question asked by jamesknox on Aug 4, 2013
I am using the MATH Integral function on a DSO5054A that is supposedly out of recent calibration.  The signal level being integrated is small, so the channel V/div is down in the 50 or 20 mV/division range.  When I use the integral function, I get a substantial sloped line, even without any signal on the channel input (grounded, no probe, or shorted).  

Looking **closely** at the screen, I seen the problem.  The trace line for zero input is VERY SLIGHTLY BELOW the small right arrow denoting the zero volt level.  In other words, all four channels are set with the arrow at the top of the "kerf" (top of the width of the horizontal trace).  Looking through the manual, I see no user way to correct this (although there is not much information).  Ironically, looking at the picture EXAMPLE of how to use the integrate function, it's clear that Agilent's example scope had the same problem !!!

Does anyone have a suggestion?  I just need some way to very slightly tweak the DC bias zero level for each channel (preferably without mucking up all the other calibration settings).