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ni.com
Chapter 3
Digital I/O
Caution
Do not make connections to the digital I/O that exceed the maximum I/O
specifications. Doing so could permanently damage the NI 6518/6519 and the
computer. Refer to the
NI 651x Specifications
, available at
ni.com/manuals
, for
information about maximum input ratings.
The input lines on the NI 6518/6519 consist of input photocouplers, which react to a voltage
differential rather than only to a voltage increase. If the voltage connected to a digital input is
either greater than or less than the voltage connected to IN.COM by at least the logic threshold,
the reading on the digital line will be logic high, even though in one instance the digital line has
a lower voltage level than IN.COM.
The output lines on the NI 6518 consist of photocouplers and Darlington arrays. To connect to
these signals, connect a 5 V to 30 V power supply to VCC, connect OUT.COM (GND) to
ground, and cross a load between digital output and OUT.COM (GND).
The output lines on the NI 6519 consist of photocouplers and Darlington arrays. To connect to
these signals, connect a 5 V to 30 V power supply to OUT.COM (VCC), connect GND to
ground, and cross a load between digital output and OUT.COM (VCC).
For more information, refer to the
