National Instruments NI 784xR - Manual (Page 27)

Chapter 2 Hardware Overview of the NI 78xxR
R Series Intelligent DAQ User Manual 2-6 ni.com
In differential input mode, signals connected to AI<0..n>– are routed to the
negative input of the instrumentation amplifier for each channel. In RSE
input mode, the negative input of the instrumentation amplifier for each
channel is internally connected to AIGND. In NRSE input mode, the
AISENSE signal is connected internally to the negative input of the
instrumentation amplifier for each channel. In DIFF and RSE input modes,
AISENSE is not used.
Caution Exceeding the differential and common-mode input ranges distorts the input
signals. Exceeding the maximum input voltage rating can damage the
NI 783xR/784xR/785xR and the computer. NI is not liable for any damage resulting from
such signal connections. The maximum input voltage ratings are listed in Table A-2,
NI 78xxR I/O Signal Summary .
AIGND is a common AI signal that is routed directly to the ground tie point
on the NI 783xR/784xR/785xR. You can use this signal for a general analog
ground tie point to the NI 783xR/784xR/785xR if necessary.
Connection of AI signals to the NI 783xR/784xR/785xR depends on the
input mode of the AI channels you are using and the type of input signal
source. With different input modes, you can use the instrumentation
amplifier in different ways. Figure 2-4 shows a diagram of the
NI 783xR/784xR/785xR instrumentation amplifier.
Figure 2-4. NI 783xR/784xR/785xR Instrumentation Amplifier
+
+
–
–
V
m
= [V
in+
– V
in–
]
V
in+
V
in–
V
m
Instrumentation
Amplifier
Measured
Voltage