Digital Interface; Relay Channels; Figure 4-2. Er-8/16 Onboard Equivalent Circuit - National Instruments ER-8 User Manual

Chapter 4

Digital Interface

There are four connectors with which to interface an ER-8/16 to digital devices or to daisy-chain
it to another ER-8/16. The two front connectors are marked DIO-24 and DIO-32; the two
internal connectors are marked IN and OUT. Use the internal connectors when daisy-chaining
the
ER-8/16 or when using SC-205X Series cable adapters.
Warning:
Use only one of the connectors—DIO-24, DIO-32, or IN—at a time. Using more
than one of these connectors can damage your host computer, DAQ device, and
the ER-8/16. National Instruments is
incorrect connections.
For additional information on signal connections, refer to Chapter 3, Signal Connections.

Relay Channels

Figure 4-2 shows the onboard equivalent circuit for the ER-8/16. When the channel receives a
digital low signal, the relay for that channel remains unenergized, the NC contact shorts to the
COM contact, and the NO contact remains open. When a digital high signal is present on a
channel, the relay for that channel is energized, the NO contact shorts to the COM contact, and
the NC contact is open.
A green LED just above each relay illuminates when the relay is energized. To reduce the power
consumption and to help extend relay life, control the signals so that relays are energized for
only short periods of time and only a minimal number of relays are energized.
© National Instruments Corporation
Digital Line
ULN 2803
High-Current Driver

Figure 4-2. ER-8/16 Onboard Equivalent Circuit

liable for any damages resulting from
NOT
+5 V
4-3
Theory of Operation
NO
COM
NC
ER-8/16 User Manual