Chapter 4
Analog Input
©
National Instruments Corporation
4-35
Using Non-Referenced Single-Ended Connections
for Ground-Referenced Signal Sources
Fig
u
re 4-23 shows how to connect gro
u
nd-reference signal so
u
rces to the
USB-6210/6211/6212 device in non-referenced single-ended mode.
Figure 4-23.
Single-Ended Connections for Ground-Referenced Signal Sources
(NRSE Configuration)
AI+ and AI– m
u
st both remain within ±11 V of AI GND.
To meas
u
re a single-ended, gro
u
nd-referenced signal so
u
rce, yo
u
m
u
st
u
se
the non-referenced single-ended gro
u
nd-reference setting. Connect the
signal to one of AI <0..31> and connect the signal local gro
u
nd reference
to AI SENSE. AI SENSE is internally connected to the negative inp
u
t of
the NI-PGIA. Therefore, the gro
u
nd point of the signal connects to the
negative inp
u
t of the NI-PGIA.
Any potential difference between the device gro
u
nd and the signal gro
u
nd
appears as a common-mode signal at both the positive and negative inp
u
ts
of the NI-PGIA, and this difference is rejected by the amplifier. If the
inp
u
t circ
u
itry of a device were referenced to gro
u
nd, as it is in the
referenced single-ended gro
u
nd-reference setting, this difference in gro
u
nd
potentials wo
u
ld appear as an error in the meas
u
red voltage.
U
S
B-6210/6211/6212 Config
u
red in NR
S
E Mode
Common-
Mode
Noi
s
e
a
nd Gro
u
nd
Potenti
a
l
Gro
u
nd-
Referenced
S
ign
a
l
S
o
u
rce
PGIA
Inp
u
t M
u
ltiplexer
s
–
+
–
+
V
s
V
cm
I/O Connector
AI GND
AI
S
EN
S
E
AI <0..15>
or AI <16..
n
>
–
+
In
s
tr
u
ment
a
tion
Amplifier
Me
asu
red
Volt
a
ge
V
m
–
+
