© National Instruments Corporation 11 NI USB-6221/6229/6251/6259 OEM User Guide
Chassis Ground
Chassis ground provides a connection between the enclosure and USB
ground.
D GND is connected to the chassis ground through an internal connection
to hole A, shown in Figure 12. The chassis ground directly connects to USB
shield ground.
The USB-6221/6229/6251/6259 OEM device includes several mounting
holes that are plated and designed for user-configured ground connections
between the device chassis ground and the appropriate system ground.
Figure 12 shows where the different grounds are connected.
Note The holes that are labeled B are reserved for an external shield. Do not use these
holes as mounting holes.
Figure 12. Ground Connections (USB-6229/6259 OEM Shown)
Mounting Hole Connected
to Chassis Ground
A
B
B
B