BNC-9920 Operating Instructions and Specifications
4
ni.com
To connect the BNC-9920 to the C Series I/O modules, complete the following steps. Refer to the
C Series module operating instructions for module-specific instructions and warnings.
Note
If you have not already installed and configured the CompactRIO system, refer to the
CompactRIO Setup and Services page. Go to
ni.com/info
and enter the Info Code
rdcriostartup
.
Caution
Using the BNC-9920 defeats electrical isolation between C Series modules.
Caution
Do
not
connect the 68-pin connector of the BNC-9920 to any device other than National
Instruments C Series modules. National Instruments is
not
liable for damage resulting from such
connections.
1.
If you plan to complete the exercises in the
CompactRIO Starter Kit Tutorial
, make sure that the
NI 9403 is in slot 1, the NI 9205 is in slot 2, and the NI 9263 is in slot 3.
2.
Place the BNC-9920 near the CompactRIO chassis or use the optional DIN Rail Mounting kit for
UMI-FLEX-6 and BNC boxes (part number 777972-01), which you can order from National
Instruments at
ni.com
.
Caution
Refer to the C Series module specifications in the documents shipped with the modules for
information about safe voltage levels and overvoltage protection.
3.
Connect the BNC-9920 to the C Series modules using the BNC-9920 cable. Connect the 68-pin
end of the cable to the BNC-9920 and the three labeled ends to the modules designated on the
labels.
4.
Connect the power end of the BNC-9920 cable to the external power supply shipped with the
CompactRIO Starter Kit. The power indicator LED, shown in Figure 1, lights. If it does not light,
check the cable connections.
5.
Connect signals to the BNC connectors and screw terminals as described in the following sections.
Use the pre-stripped wires in the CompactRIO Starter Kit to connect signals to the screw terminals.
If you need additional wires, use 28–16 AWG wire with the insulation stripped to 0.28 in.
When you have finished using the BNC-9920, power off any external signals connected to the
BNC-9920 before you power off the CompactRIO system.
Connecting Analog Input Signals
You can use the analog input BNC connectors on the BNC-9920 in the following ways:
•
Measure differential AI signals, as described in the
Connecting Differential Analog Input Signals
section
•
Measure temperature, as described in the
section
•
Measure resistance, as described in the
section
Note
If you are using the NI 9205 in Scan Interface programming mode, scanned channels that are
unconnected (floating) can cause noise on subsequently scanned channels. In order to avoid noisy
measurements, connect COM to a ground reference, and ensure that any AI channel with a lower
number than the one you are measuring is connected either to a signal or to ground.
Connecting Differential Analog Input Signals
Use the BNC-9920 BNC connectors on the front panel to connect differential analog input signals to
channels AI <0..7> of the NI 9205. The BNC-9920 is intended
only
for differential analog input signals.
