National Instruments NI 7831R - Manual (Page 24)

Chapter 2 Hardware Overview of the NI 7831R
© National Instruments Corporation 2-5 NI 7831R User Manual
Connecting Analog Input Signals
The AI signals for the NI 7831R are AI<0..7>+, AI<0..7>–, AIGND, and
AISENSE. The AI<0..7>+ and AI<0..7>– signals are connected to the
eight AI channels of the NI 7831R. For all input modes, the AI<0..7>+
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.
In differential input mode, signals connected to AI<0..7>– 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 7831R and the
computer. NI is not liable for any damage resulting from such signal connections. The
maximum input voltage ratings are listed in Table B-2,
NI 7831R I/O Signal Summary .
AIGND is a common AI signal that is routed directly to the ground tie point
on the NI 7831R. You can use this signal for a general analog ground tie
point to the NI 7831R if necessary.
Connection of AI signals to the NI 7831R 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 7831R
instrumentation amplifier.