You must connect an external power supply to the NI 9871. This
power supply provides the power for the RS485/RS422
transceivers on the module. You can use the included female
four-position pigtail to connect to an external voltage source.
Figure 1 lists the connections between an external voltage source
(of +8 V to +28 V) and the NI 9871.
Caution
To ensure the specified EMC performance,
do not connect the power input to a DC mains supply
or to any supply requiring a connecting cable longer
than 30 m (100 ft). A DC mains supply is a local DC
electricity supply network in the infrastructure of a
certain site or building.
NI 9871 Getting Started Guide
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© National Instruments
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