Chapter 3 Connector and LED Information
© National Instruments Corporation 3-4 NI USB-621x User Manual
USB Chassis Ground
(USB-621x BNC Devices) For EMC compliance, the chassis of the USB-621x
BNC device must be connected to earth ground through the chassis ground.
The wire should be AWG 16 or larger solid copper wire with a maximum
length of 1.5 m (5 ft). Attach the wire to the earth ground of the facility’s
power system. For more information about earth ground connections, refer
to the KnowledgeBase document, Earth Grounding for Test and
Measurement Devices, by going to
ni.com/info and entering the info
code
earthground.
You can attach a wire to the ground lug screw of any USB-621x BNC
device, as shown in Figure 3-1.
Figure 3-1. Grounding a USB-621x BNC Device through the Ground Lug Screw
USB Device Fuse Replacement
(USB-621x Mass Termination Devices) USB-621x Mass Termination devices
have a replaceable 0.75A,125V fuse (Littelfuse part number 0453.750) that
protects the device from overcurrent through the +5 V terminal(s).
To replace a broken fuse in the USB-621x Mass Termination, complete the
following steps while referring to Figure 3-2.
1. Remove the USB cable and any I/O signal wires from the device.
2. Remove the four Phillips screws on the bottom of the device to remove
the device top. You may have to remove the rubber feet.
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