National Instruments NI 9233

Each channel has a BNC connector to which you can connect an

Integrated Electronic Piezoelectric (IEPE) sensor. The center pin

of the connector, AI+, provides the DC excitation and the AC

signal connection. The shell of the connector, AI–, provides the

excitation return path and the AC signal ground reference.

You can connect ground-referenced or floating IEPE sensors to the

NI 9233. You can avoid picking up ground noise by using a floating

connection. Typical IEPE sensors have a case that is electrically

isolated from the IEPE electronics, so connecting the sensor to the

NI 9233 results in a floating connection even though the case of the

sensor is grounded. To further minimize ground noise, prevent

themetal shells of the BNC connectors from touching each other,

the modules, or the chassis.

If you make a ground-referenced connection between the IEPE

sensor and the NI 9233, make sure the voltage on the AI– shell

isin the common-mode range to ensure proper operation of the

NI9233. The AI– shell is protected against accidental contact

withovervoltages within the overvoltage protection range. Refer

tothe Specifications section for more information about operating

voltages and overvoltage protection. Figures2 and 3 illustrate

connecting grounded and floating IEPE sensors to the NI 9233.