Watlow CAS - Manual (Page 68)

58 CAS User’s Guide
Setup
• High process and high deviation alarms activate when the process
variable goes above a value you set. They remain active until the
process variable goes below that value minus the deadband. (See the
diagram below.)
• Any digital output can be assigned to one or more process variable
alarms. The output is active if any of its alarms are active. All alarm
outputs are active Low or active High, depending on the global
alarm output polarity setting.
• Low process and low deviation alarms activate when the process
variable goes below a value you set. They remain active until the
process variable goes above that value plus the deadband. (The dia-
gram below shows these alarms.)
When the scanner powers up or the setpoint changes, deviation alarms
do not activate until the process goes inside the deviation alarm band,
preventing deviation alarms during a cold start. (High and low process
alarms are always enabled.)
Use menus to set the following process alarm parameters for each
channel:
• High and low process alarm type, setpoint, and digital output
• High and low deviation alarm type, deviation alarm value, and digi-
tal output
• Alarm deadband
• Alarm delay
The setpoints, deviation alarm values, and deadband all use the same
decimal format as the channel's process variable.
High Alarm Limit
Setpoint
Low Alarm Limit
SP + Deviation
SP - Deviation
} Deadband
} Deadband
} Deadband
} Deadband
High deviation alarm on
High deviation alarm off
Low deviation alarm on
Low deviation alarm off
High process alarm off
High process alarm on
Low process alarm on
Low process alarm off