National Instruments NI 9234, Operating Instructions Manual, Page: 7 / 36

© National Instruments Corp. 7 NI 9234 Operating Instructions and Specifications
Each channel has a BNC connector to which yo u can connect
a signal so u rce. Yo u can also enable excitation c u rrent on a
per-channel basis to connect Integrated Electronics Piezoelectric
(IEPE) sensors. Refer to the
NI 9234 Circuitry section for more
information. The center pin of the connector, AI+, provides the DC
excitation, when enabled, and the positive inp
u t signal connection.
The shell of the connector, AI–, provides the excitation ret u rn path
and the signal gro u nd reference.
Connecting Signal Sources to the NI 9234
Yo u can connect gro u nd-referenced or floating signal so u rces to
the NI 9234. To avoid picking u p gro u nd noise, u se a floating
connection. To f u rther minimize gro u nd noise, prevent the metal
shells of the BNC connectors from coming in contact with each
other, the mod
u les, or the chassis.
If yo u make a gro u nd-referenced connection between the signal
so u rce and the NI 9234, make s u re the voltage on the AI– shell
is in the common-mode range to ens u re proper operation of the
NI 9234. The AI– shell is protected against accidental contact with
overvoltages within the overvoltage protection range. Refer to the
Specifications section for more information abo u t operating
voltages and overvoltage protection.