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3-3
The input lines on the NI 6514/6515 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 P
X
.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 P
X
.COM.
The output lines on the NI 6514 consist of photocouplers and Darlington arrays. To connect to
these signals, connect a 5 V to 30 V power supply to VCC, connect COM (GND) to ground, and
cross a load between digital output and COM (GND).
The output lines on the NI 6515 consist of photocouplers and Darlington arrays. To connect to
these signals, connect a 5 V to 30 V power supply to COM (VCC), connect GND to ground, and
cross a load between digital output and COM (VCC).
For more information, refer to the
NI 6516/6517 I/O Connector
The 37-pin D-SUB connector on the NI 6516/6517 provides access to the digital inputs and
outputs. The digital I/O available on this connector includes 32 outputs. For easy connection to
the digital I/O connector, use the National Instruments SH37F-37M shielded digital I/O cable
with the CB-37F connector block. For more information on digital I/O connectivity options,
refer to Chapter 5,
.
Caution
Do not make connections to the digital I/O that exceed the maximum I/O
specifications. Doing so could permanently damage the NI 6516/6517 and the
computer. Refer to the
NI 651x Specifications
, available at
ni.com/manuals
, for
information about maximum input ratings.
The output lines on the NI 6516 consist of photocouplers and Darlington arrays. To connect to
these signals, connect a 5 V to 30 V power supply to VCC, connect COM (GND) to ground, and
cross a load between digital output and COM (GND).
The output lines on the NI 6517 consist of photocouplers and Darlington arrays. To connect to
these signals, connect a 5 V to 30 V power supply to COM (VCC), connect GND to ground, and
cross a load between digital output and COM (VCC).
For more information, refer to the
NI 651
8
/6519 I/O Connector
The 37-pin D-SUB connector on the NI 6518/6519 provides access to the digital inputs and
outputs. The digital I/O available on this connector includes 32 inputs and 32 outputs. For easy
connection to the digital I/O connector, use the National Instruments SH37F-37M shielded
digital I/O cable with the CB-37F connector block. For more information on digital I/O
connectivity options, refer to Chapter 5,