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Chapter 4
Analog Input
4-4
ni.com
with this amplified voltage. The amo
u
nt of amplification (the gain) is
determined by the analog inp
u
t range, as shown in Fig
u
re 4-2.
Figure 4-2.
NI-PGIA
Table 4-1 shows how signals are ro
u
ted to the NI-PGIA.
For differential meas
u
rements, AI 0 and AI 8 are the positive and negative
inp
u
ts of differential analog inp
u
t channel 0. For a complete list of signal
pairs that form differential inp
u
section of Chapter 3,
.
AI gro
u
nd-reference setting is sometimes referred to as AI terminal
config
u
ration.
Caution
The maxim
u
m inp
u
t voltages rating of AI signals with respect to AI GND
(and for differential signals with respect to each other) are listed in the
NI USB-621x
Specifications
. Exceeding the maxim
u
m inp
u
t voltage of AI signals distorts the
meas
u
rement res
u
lts. Exceeding the maxim
u
m inp
u
t voltage rating also can damage the
device and the comp
u
ter. NI is
not
liable for any damage res
u
lting from s
u
ch signal
connections.
Table 4-1.
Signals Routed to the NI-PGIA
AI Ground-Reference
Settings
Signals Routed to the Positive
Input of the NI-PGIA (V
in+
)
Signals Routed to the Negative
Input of the NI-PGIA (V
in–
)
RSE
AI <0..31>
AI GND
NRSE
AI <0..31>
AI SENSE
DIFF
AI <0..7>
AI <8..15>
AI <16..23>
AI <24..31>
V
in+
V
m
= [V
in+
– V
in–
]
×
G
a
in
V
m
V
in–
PGIA
+
–
Me
asu
red
Volt
a
ge
In
s
tr
u
ment
a
tion
Amplifier