Rockwell Automation 900-TC32 Digital Temperature Controllers, Series B - Manual (Page 144)

Publication 900-UM007D-EN-E - January 2011
4-8 Parameter Adjustments & Application Considerations
Alarm Functions/
Parameters Alarm Hysteresis
You can configure/program how much deviation (hysteresis) is allowed from
the alarm value before the alarm comes on and reset.
The hysteresis of alarm outputs when alarms are switched ON/OFF can be
set as follows:
Figure 4.15 — Hysteresis of Alarm Outputs
Alarm hysteresis is independently set for each alarm output in the Alarm
Hysteresis 1…3 parameters (Advanced Setting function group).
Note: The default is 0.2 (°C or °F depending on your units selection) for
temperature inputs and 0.02% of full scale (FS) for analog inputs.
Standby Alarm Sequence
Standby alarm sequence is a function which allows you to configure the alarm
outputs to be temporarily disabled until after the first alarm condition occurs.
From then on, the alarm output is active for all future alarm conditions.
For example, in a standard heating application, if you used the standard low
alarm configuration, the alarm would be active as soon as you switch the
controller ON. However, with standby sequence, the alarm output is disabled
during the first warm-up, and the temperature has to rise above the alarm set
point before the alarm can become active. Then, if the temperature falls below
the alarm set point, the output is active.
Restart
As mentioned above, the standby sequence is canceled after the first real
alarm clears. If desired, it can be restarted later by the Standby Sequence
parameter (Advanced Setting function group). For details, refer to page 5-72,
Standby Sequence Reset Method
.
ON
OFF
ON
OFF
Normal
Operating
Area
SP
Normal
Operating
Area
SP
Alarm Value Alarm Value
Alarm Hysteresis Alarm Hysteresis
Upper-Limit
Alarm Lower-Limit
Alarm