User manual

UniversitàdegliStudidiCatania
IntroductiontoNILabVIEW
 DAQ:VoltageSources
A
groundedsourceisoneinwhichthevoltagesignalsareref erenced
toasystemground,suchasearthorbuildingground.Becausetheyuse
thesystemground,theysharea commongroundwiththeDAQdevice.
Themostcommonexamplesofgroundedsourcesaredevicesthatplug
intothebuildinggroundthroughwalloutlets,suchassignal generators
andpowersupplies.
The DAQ devices in your computer are also expecting to measure voltage with respect to some
reference. What reference should the DAQ device use? You have your choice, which will depend on the
kind of signal source you're connecting. Signals can be classified into two broad categories, as follows:
A floating source is a source i n which the voltage signal is not
referenced to any common ground, such as earth or building ground.
Some common examples of floating signal sources are batteries,
thermocouples, transformers, and isolation amplifiers. Notice that
neither terminal of the source is connected to the electrical outlet
ground. Thus, each terminal is independent of the system ground.
Tomeasureyoursignal,youcanalmostalwaysconfigureyourDAQdevicetomake
measurementsthatfallintooneofthesethreecategories:Differential,ReferencedSingle
Ended,Nonreferenced Single‐Ended
DIEEI