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© National Instruments Corporation 13 NI USB-9421 User Guide and Specifications
Figure 8. Connecting a Device to the NI USB-9421 (3-Wire Device Shown)
The NI USB-9421 channel registers as ON when the sourcing-output
device applies a voltage or drives a current to DI that is in the input ON
range. The channel registers as OFF when the device applies a voltage or
drives a current to DI that is in the input OFF range. If no device is
connected to DI, the channel registers as OFF. The channel LED turns on
and off to indicate the state of the channel. Refer to the Specifications
section for more information about ON and OFF ranges.
Assembling the High Voltage Screw Terminal Backshell
The NI 9932 high voltage screw terminal backshell must be installed when
using hazardous voltages (>42.4 V
pk
, 60 VDC). Refer to Figure 9 while
completing the following steps to assemble the backshell:
1. Connect the leads to the screw terminal and secure with the strain
relief.
2. Finish by snapping the backshell around the connector.
Figure 9. High Voltage Screw Terminal Backshell
1 Strain Relief
NI USB-9421
+
_
Sourcing-Output
Device
COM
DI
External
Power
Supply
1