National Instruments NI 784xR - Manual (Page 26)

Chapter 2 Hardware Overview of the NI 78xxR
© National Instruments Corporation 2-5 R Series Intelligent DAQ User Manual
Input Modes
The NI 783xR/784xR/785xR input mode is software configurable. The
input channels support three input modes—differential (DIFF), referenced
single ended (RSE), and nonreferenced single ended (NRSE). The selected
input mode applies to all the input channels. Table 2-2 describes the three
input modes.
Input Range
The NI 783xR/784xR/785xR AI range is fixed at
±10 V.
Connecting Analog Input Signals
The AI signals for the NI 783xR/784xR/785xR are AI<0..n>+, AI<0..n>–,
AIGND, and AISENSE. For the NI 7830R, n=4. For the
NI 7831R/7833R/784xR/785xR, n=8. The AI<0..n>+ and AI<0..n>–
signals are connected to the eight AI channels of the
NI 783xR/784xR/785xR. For all input modes, the AI<0..n>+ signals are
connected to the positive input of the instrumentation amplifier on each
channel. The signal connected to the negative input of the instrumentation
amplifier depends on how you configure the input mode of the device.
Table 2-2. Available Input Modes for the NI 783xR/784xR/785xR
Input Mode Description
DIFF When the NI 783xR/784xR/785xR is configured in DIFF input mode, each
channel uses two AI lines. The positive input pin connects to the positive terminal
of the onboard instrumentation amplifier. The negative input pin connects to the
negative input of the instrumentation amplifier.
RSE When the NI 783xR/784xR/785xR is configured in RSE input mode, each
channel uses only its positive AI pin. This pin connects to the positive terminal
of the onboard instrumentation amplifier. The negative input of the
instrumentation amplifier connects internally to the AI ground (AIGND).
NRSE When the NI 783xR/784xR/785xR is configured in NRSE input mode, each
channel uses only its positive AI pin. This pin connects to the positive terminal
of the onboard instrumentation amplifier. The negative input of the
instrumentation amplifier on each AI channel connects internally to the
AISENSE input pin.