Hi Scott,
The property node that you are referring to, "Actual Excitation Value", has a deceiving description. This property node is actually meant to be used when you are using an external excitation source, so that you can tell the DAQmx strain channel the actual excitation value that is being sourced externally, so that this number can be used when scaling the strain measurements. The value of 2.5 that you are reading is just the default value for this property and has no association with the voltage being output from the internal excitation source.
The Remote Sense functionality of the SCXI-1520 is actually built-in to the hardware so that when you set the excitation to be 5V, for example, the amplifier will automatically adjust its output until the voltage read across RS+ and RS- equal 5V. So, using remote sense is useful if you have very long leads on your strain gage so that you can account for the voltage loss across those leads.
If you want to read the actual values at the P+ and P- terminals for each channel on the 1520, you can add those channels to your task and read them at the same time that you are reading your normal strain measurements. The channels that you will need to add to your task are internal channels called _pPosX or _pNegX, which are the positive and negative excitations for channel X. There is another discussion forum which addressed this same question, and in that discussion Brian attached some helpful example programs for demonstrating how to read those excitation values into LabVIEW. Here is the link to that discussion forum:
http://forums.ni.com/ni/board/message?board.id=300&message.id=1354&requireLogin=False-Logan
