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Configuring Floating or Ground-Referenced Signals
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Before installing and using the terminal block, you must determine what
type of signal sources are in the SCXI system. Signal sources are either
floating or ground-referenced.
A floating source is not connected in any way to the building ground
system and has an isolated ground-reference point that you cannot assume
is at the same potential as any other ground. Examples of floating sources
include transformers, insulated thermocouples, optical isolators, isolation
amplifiers, and battery-powered devices.
A ground-referenced source is connected to the building ground and shares
a common ground with the DAQ device, assuming the computer is
connected to the building power supply. Examples of ground-referenced
signals are the nonisolated outputs of any device that plugs into the building
power supply, such as signal generators and power supplies. Isolated
outputs do not constitute ground-referenced sources and are treated as
floating sources.
Reference an input signal to ground at only one point. Do not reference the
input of a differential amplifier module to ground if the signal source is
already ground-referenced. If you are measuring a floating source,
reference the input to ground.
3
SCXI-1305 Installation Guide
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