Hello gpibssx,
Before you do anything, you will want to change the vertical range on your 5112 so you don't have so much digitizing noise. You have a signal with a 1V range and are using the 10V range of the digitizer. The 5112 has a new range every 10% - take advantage of it. Set the vertical range to about 1.1V and the offset to about 0.25V. This will maximize your resolution. Now you are ready for some measurements.
I will give you two options - one interactive and one "automatic". First, the interactive one, since it is relatively easy. Set up your graph so it shows three cursors (you can display the cursor palette and do it from there or programatically using the graph property node). While running, move the cursors to the levels of interest (bottom, top, and zero blanking). Using property nodes from the graph, programatically pick off the Y values of the cursors, do the math, and you are done.
The second method is a bit more complex, but, with a bit of tweaking, will work more or less automatically. It will require a more or less known video signal, but it appears you have that. First, convert your waveform into a voltage histogram. You can do this by using the measurement functions in NI-SCOPE or the LabVIEW analysis VIs. Fetch the data as binary and set the histogram to 256 levels ranging from -128 to 127. This covers the actual binary range of the 8 bit digitizer. In the resultant histogram, the bottom, top, and zero blanking levels should show up as peaks. Use any of the peak finding routines in the LabVIEW library to find them. You could easily have other peaks from the video portion of your waveform, so you may have to toss out a few things. This is why it is important to keep the same waveform. After you find the peak values, multiply them by the scale and offset from the NI-SCOPE fetch to convert from binary to Volts, then do the math to get the voltage differences.
There are probably other algorithms, as well, but these two should get you started. Don't be surprised if it takes awhile to get working well. Data analysis routines of this type usually require some tweaking. Good luck!
