Appendix A
Device-Specific Information
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
sections of Chapter 2,
, 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
µ
F 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