Mechanical Relays; Relay Forms; Non-Latching Relays; Relay Power Ratings - National Instruments NI 6520 User Manual

Mechanical Relays

Form Symbol
Form A
Form C
Caution The maximum switching current is limited by the maximum switching power, the
maximum voltage, and must not exceed 60 W, 60 VA.
© National Instruments Corporation

Relay Forms

Table 4 describes the relay forms available on the NI 6520/6521.
Table 4. NI 6520/6521 Relay Forms
Single-pole single-throw (SPST) relays with a default state of
normally open.
Single-pole double-throw (SPDT) relays that break the
NC
connection with one throw before making contact with the other
NO
(break-before-make).

Non-Latching Relays

The relays on the NI 6520/6521 are non-latching. A non-latching relay has
an initial position of normally closed (NC). This position is maintained by
the force of a spring or permanent magnet while no current flows. The
normally open (NO) contact is closed by the force of a magnetic field while
current flows through the coil. When the current stops, the relay reverts
back to its initial NC position.
Non-latching armature relays are useful in control applications when the
switch must return to a known state if power is lost.
NC Position
Figure 8. Non-Latching Relay States

Relay Power Ratings

The maximum power rating for the NI PCI-6520 relays is
(NI PCI-6520 Only)
60 W or 60 VA, with a maximum current of 2 A for all channels from 0 to
55 °C, external PC ambient.
Description
NC
COM
NO
NO Position
15
NC
COM
NO
NI 6520/6521 User Guide