Chapter2 NI2590/2591 Operation
©NationalInstruments Corporation 2-5 NI2590/2591 User Manual
Relay Operation

NI 2590 Operation

The NI 2590 has four channels, CH0 through CH3, any one of which can
be connected to the single common channel (COM) by closing the
appropriate relays.
Youcan control the relays individually, or you can use higher-level
commandsto energize the correct relays to connect a channel (such as
CH0)to COM. Only one channel can be connected to the common channel
atany time, and it is not possible to connect one channel t o another channel
bypassingthe comm on channel.
TheNI 2590relays are single-side stable. When power is removed from the
relaycoil, the relay returns to its de-energized state. When all three relays
arede-energized, the default connection is from CH0 to COM, as shown in
Figure 2-1. Toconnect CH2 to COM, you energize MUX0123; to connect
CH3 toC OM, youenergize MUX0123 and MUX23. You can specify the
channel to connect to COM and let the NI-Switch driverenergize the
appropriaterelays for you. Refer to the NI-SWITCH Software User Manual
for further information.

NI 2591 Operation

The NI 2591 is very similar to the NI 2590 in some respects, but different
inothers. The NI 2591 has 4 channels, CH0 through CH3, any one of which
can be connected to the single COM by closing theappropriate relays.
The NI 2591 does not allowfor control of t he individualrelays. You must
use the high-levelcommands to connect the channels, such as CH2 to
COM. Only one channel can be connected to the common channel at any
time, and it is not possible to connect one channel to another channel,
bypassingthe common channel. The default (power off) connection of the
NI2591 is CH3 to COM. Refer to Figure 2-2 to see how the connections in
the NI 2591 are made.