Watlow CAS - Manual (Page 31)

Installation
CAS User’s Guide 21
Alarm Output Connections
Typical digital outputs use external optically isolated solid-state relays
(SSRs). The SSRs use a 3 to 32 Vdc input for control, and you can size
them to switch up to 100 amps at 480 Vac. For larger currents, you can
use optically isolated relays to drive contactors.
NOTE
Digital outputs are SINK outputs. They are Low when the output is
On. Connect them to the negative side of Solid State Relays.
The figure below shows sample alarm output connections.
Watchdog Timer
The CAS watchdog timer monitors the CAS microprocessor. It is a sink
output located on TB-50 terminal #6. (Do not exceed the rating for the
watchdog timer.) Its output is Low (on) when the microprocessor is
operating; when it stops operating, the output goes High (off), which de-
energizes the SSR.
Here's the recommended circuit for the watchdog timer output:
Digital Output
+5 Vdc
SSR
SSR
+5 Vdc
(TB-50 Pin 1)
W atchdog Tim er
(TB-50 Pin 6)