National Instruments Data Acquisition Device E Series - Manual (Page 207)

Appendix A Device-Specific Information
E Series User Manual A-72 ni.com
Differential Signals
To connect differential signals, determine the type of signal source you are
using: a floating signal source or a ground-referenced signal source. Refer
to the
Differential Connection Considerations and Connecting Analog
Input Signals sections of Chapter 2, Analog Input , for more information on
AI signals.
To measure a floating signal source, move the switch to the FS position. To
measure a ground-referenced signal source, move the switch to the GS
position. Figure A-57 shows the source type switch locations on the front
panel of the BNC DAQPads.
Figure A-57. BNC DAQPad Front Panel
Figure A-58 shows the analog input circuitry on BNC DAQPads. When the
switch is in the FS position, AI x – is grounded through a 0.1
μF capacitor
in parallel with a 5 k
Ω resistor.
Figure A-58. Analog Input Circuitry
FS GS FS GS FS GS FS GS
FS GS FS GS FS GS FS GS
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
USER 2
USER 1
PWR COM
CTR 0 OUT EXT
REF DAC 0 OUT ACH 6 ACH 4 ACH 2 ACH 0
ACH 1 ACH 3 ACH 5 ACH 7 DAC 1 OUT PFI 0/ TRIG 1
FS GS
FLOATING SOURCE GND REF SOURCE
FS GS
Source Type
Switch
Source Type
Switch
FS = Floating Source
GS = Grounded Source
AI x +
AI x –
GS
0.1 µF 5 k Ω
AI GND
FS