JYTEK USB-62401, Руководство пользователя

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28 Operation
3.2.2 Ground-Referenced Signal Source
Connected in some way to the existing ground system, to a common
ground point with respect to the USB DAQ, when the computer is
connected to the same power system. Non-isolated output of
instruments and devices connected to the existing power systems
are ground-referenced signal sources.
3.3 Signal Connection
Each analog input channel can be configured to different input modes by
the software API. Details of signal connection in different input modes
follow.
3.3.1 Voltage Input Mode
The properties of the signal to be measured must be considered. The
differential input mode provides two inputs that respond to signal
voltage difference between them. If the signal source is
ground-referenced, the differential mode can be used for the
common-mode noise rejection.
Connection of ground-referenced signal sources under differential input
mode is as shown.
Figure 3-2: Ground-Referenced Source and Differential Input
For floating signal sources, addition of a resistor at each channel
provides a bias return path. The resistor value should be about 100