Campbell Scientific A21REL-12 Relay Driver - Manual (Page 3)

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A21 REL-12 RELAY DRIVER
FUNCTION:
Provide drive capability for four external relays
controlled by the CR10, 21X, or CR7
dataloggers. The A21 REL-12 is powered by a
12 V source on the relay coil.
CONTACT RATING:
DC - 1 Amp at 20 V
AC - 0.3 Amp at 120 V
COIL CURRENT:
13 mA/relay
CONNECTIONS:
+12 V External 12 V source
Ground Low side of external source
REL COM Low side of device under control
REL NC Normally closed relay output to
device under control
CTRL To datalogger control port. When
presented with 5 V, REL NC and
REL NO invert their normal states
until CTRL goes to 0V at which time
REL NC and REL NO return to
normal states.