National Instruments NI USB-621x - Manual (Page 24)

© National Instruments Corporation 3-1 NI USB-621x User Manual
3
Connector Information
The I/O Connector Signal Descriptions and +5 V Power sections contain
information about NI 621x connectors. Refer to Appendix A,
Device-Specific Information , for device I/O connector pinouts.
I/O Connector Signal Descriptions
Table 3-1 describes the signals found on the I/O connectors. Not all signals
are available on all devices.
Table 3-1. I/O Connector Signals
Signal Name Reference Direction Description
AI GND — — Analog Input Ground—These terminals are the
reference point for single-ended AI measurements in
RSE mode and the bias current return point for DIFF
measurements. All three ground references—AI GND,
AO GND, and D GND—are connected on the device.
AI <0..31> Varies Input Analog Input Channels 0 to 31—For single-ended
measurements, each signal is an analog input voltage
channel. In RSE mode, AI GND is the reference for these
signals. In NRSE mode, the reference for each
AI <0..31> signal is AI SENSE.
For differential measurements, AI 0 and AI 8 are the
positive and negative inputs of differential analog input
channel 0. Similarly, the following signal pairs also form
differential input channels:
<AI 1, AI 9>, <AI 2, AI 10>, <AI 3, AI 11>,
<AI 4, AI 12>, <AI 5, AI 13>, <AI 6, AI 14>,
<AI 7, AI 15>, <AI 16, AI 24>, <AI 17, AI 25>,
<AI 18, AI 26>, <AI 19, AI 27>, <AI 20, AI 28>,
<AI 21, AI 29>, <AI 22, AI 30>, <AI 23, AI 31>
AI SENSE — Input Analog Input Sense—In NRSE mode, the reference for
each AI <0..31> signal is AI SENSE.
AO <0..1> AO GND Output Analog Output Channels 0 to 1—These terminals
supply the voltage output of AO channels 0 to 1.