2.5 - GND and SGND [UE9 Datasheet] | LabJack
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2.5 - GND and SGND [UE9 Datasheet]

The GND connections available at the screw-terminals and DB connectors provide a common ground for all LabJack functions. All GND terminals are the same and connect to the same ground plane. This ground is the same as the ground line on the USB connection, which is often the same as ground on the PC chassis and therefore AC mains ground. This ground is also the same as the ground on either Vext connections (wall-wart power jack or minus screw terminals), but if an isolated supply is used, such as the one included with the UE9, there is no common connection to AC mains ground.

SGND is located near the upper-left of the device. This terminal has a self-resetting thermal fuse in series with GND. This is often a good terminal to use when connecting the ground from another separately powered system that could unknowingly already share a common ground with the UE9.

The UE9 has separate ground planes on the PCB for analog and digital, but the planes are shorted together so the user only has to consider one common ground (GND).

See the AIN, DAC, and Digital I/O Sections for more information about grounding.