+5 V Power; +5 V Power As An Output; +5 V Power As An Input; Usb Device Fuse Replacement - National Instruments Data Acquisition Device NI USB-621x User Manual

Chapter 3 Connector and LED Information

+5 V Power

+5 V Power as an Output

+5 V Power as an Input

USB Device Fuse Replacement

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USB-621x Screw Terminal devices have a 350 mA self-resetting fuse. USB-621x Mass Termination devices have a 750 mA
user-replaceable socketed fuse.
NI USB-621x User Manual
The +5 V terminals on the I/O connector can be use as either an output or
an input. Both terminals are internally connected on the USB-621x.
Because the USB-621x devices are bus powered, there is a 50 mA limit on
the total current that can be drawn from the +5 V terminals and the digital
outputs. The USB-621x monitors the total current and drops the voltage
on all of the digital outputs and the +5 V terminals if the 50 mA limit is
exceeded.
If you have high current loads for the digital outputs to drive, you can
exceed the 50 mA internal limit by connecting an external +5 V power
source to the +5 V terminals. These terminals are protected against
undervoltage and overvoltage, and they have a fuse to protect them from
short circuit conditions
terminal, you can connect the external power supply to one terminal and
use the other as a power source.
(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 3-1.
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.
1
. If your USB-621x device has more than one +5 V
USB-621x Mass Termination devices
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