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Chapter 3
Connector and LED Information
©
National Instruments Corporation
3-4
USB Chassis Ground
(USB-621
x
BNC Devices)
For EMC compliance, the chassis of the USB-621
x
BNC device
must
be connected to earth gro
u
nd thro
u
gh the chassis gro
u
nd.
The wire sho
u
ld be AWG 16 or larger solid copper wire with a maxim
u
m
length of 1.5 m (5 ft). Attach the wire to the earth gro
u
nd of the facility’s
power system. For more information abo
u
t earth gro
u
nd connections, refer
to the KnowledgeBase doc
u
ment,
Earth Grounding for Test and
Measurement Devices
, by going to
ni.com/info
and entering the info
code
earthground
.
Yo
u
can attach a wire to the gro
u
nd l
u
g screw of any USB-621
x
BNC
device, as shown in Fig
u
re 3-1.
Figure 3-1.
Grounding a USB-621
x
BNC Device through the Ground Lug Screw
USB Device Fuse Replacement
(USB-621
x
Mass Termination Devices)
USB-621
x
Mass Termination devices
have a replaceable 0.75A,125V f
u
se (Littelf
u
se part n
u
mber 0453.750) that
protects the device from overc
u
rrent thro
u
gh the +5 V terminal(s).
To replace a broken f
u
se in the USB-621
x
Mass Termination, complete the
following steps while referring to Fig
u
1.
Remove the USB cable and any I/O signal wires from the device.
2.
Remove the fo
u
r Phillips screws on the bottom of the device to remove
the device top. Yo
u
may have to remove the r
u
bber feet.