There are 2 switches FS and GS on the NI USB-6229 data logger but I don’t know which one I switch when using it?
so I searc on NI net.
Find these:
FS = Floating Source
GS = Ground Referenced Source
There is a example about it:
If the source you are trying to measure is floating (such as a battery) then you will want to use the FS setting. If you source you are trying to measure is referenced to ground then you will use the GS setting.