User manual

UniversitàdegliStudidiCatania
IntroductiontoNILabVIEW
 DAQ:Differentialterminalconfiguration
In a differential measurement system, neither input is connected to a fixed reference s uch as
earth or building ground. Most DAQ devices with instrumentation amplifier can be configured as
differential measurement systems. The figure above depicts the eight‐channel differential
measurementsystemusedintheE‐series DAQ devices. Analog multiplexers increase the number of
measurement channels while still using a single instrumentation amplifier. For this device, the pin
labeled AIGND (the analog input ground) is the measurement system ground.
An ideal diff erential measurement system reads only the potential
difference between its two terminals the (+) and (‐). Any voltage
present at the instrumentation amplifier inputs with respect to
the amplifier ground is referred to as a common‐mode voltage. An
ideal differential measurement system completely rejects (does
not measure) common‐mode voltage.
DIEEI