National Instruments FP-RLY-420 - Manual (Page 4)

FP-RLY-420 4 www.natinst.com
Figures 2a and 2b show examples of basic wiring connections.
Figure 2. Basic Field Connection (Two Channels Shown)
Relay Output Circuit
The outputs of the FP-RLY-420 consist of Form A
electromechanical relays. The power-up state is off (open) to
ensure safe installation. In the ON state, the N.O. and I.C. contacts
connect together to form a short circuit. Choose the impedance of
the loads so that the current switched by any one channel in the ON
state is no more than 3 A.
In the ON state, there is an effective resistance of 100 m
Ω
between
the N.O. and I.C. terminals, which causes a voltage drop. For
example, if the current is 3 A, the voltage drop across the N.O.
and I.C. terminals is 0.3 V.
V C
V
sup
–
+
N.O.
N.O.
I.C.
a. Total Current Less
Than 6 Amps
I.C.
COM
V
sup
N.O.
I.C.
COM
Load
b. Total Current Greater
Than 6 Amps
Load
–
+
Load
N.O.
I.C. –
+ Load