ADLINK DAQe-2006 - Manual (Page 38)

26 Signal Connections
3.2 Analog Input Signal Connection
The DAQ-/DAQe-/PXI-2016/2010/2006/2005 card provides 4 dif-
ferential analog input channels. The analog signal can be con-
verted to digital values by the A/D converter. To avoid ground
loops and get more accurate measurements from the A/D conver-
sion, it is quite important to understand the signal source type and
how to connect the analog input signals.
Types of signal sources
Ground-Referenced Signal Sources
A ground-referenced signal means it is connected in some way
to the building system. That is, the signal source is already
connected to a common ground point with respect to the DAQ-
/DAQe-/PXI-2016/2010/2006/2005 card, assuming that the
computer is plugged into the same power system. Non-isolated
out-puts of instruments and devices that plug into the buildings
power system are ground-referenced signal sources.
Floating Signal Sources
A floating signal source means it is not connected in any way to
the buildings ground system. A device with an isolated output is
a floating signal source, such as optical isolator outputs, trans-
former outputs, and thermocouples.
Single-Ended Measurements
For single-ended connection, the analog input signal is referenced
to the common ground of the system. In this case, all the negative
ends of analog input channels should be connected to the AIGND
on the connector in-stead of floating. Refer to Figure 3-1.