National Instruments NI 9229 - Manual (Page 9)

© National Instruments Corp. 9 NI 9229/9239
The NI 9229/9239 has four 2-terminal detachable screw-terminal
connectors.
Note You must use 2-wire ferrules to create a secure
connection when connecting more than one wire to a
single terminal on the NI 9229/9239.
You can connect ground-referenced or floating signal sources to
the NI 9229/9239. Connect the positive signal of the signal source
to the AI+ terminal or connector, and connect the negative signal
of the signal source to the AI– terminal or connector. If you make
a ground-referenced connection between the signal source and the
NI 9229/9239, make sure the voltage on the AI+ and AI–
connections are in the channel-to-earth safety voltage range to
ensure proper operation of the NI 9229/9239. Refer to the
Specifications section for more information about operating
voltages and overvoltage protection. Refer to Figures 3 and 4 for
illustrations of how to connect grounded and floating signal
sources to the NI 9229/9239.