Rockwell Automation 900-TC32 Digital Temperature Controllers, Series B - Manual (Page 105)

Publication 900-UM007D-EN-E - January 2011
Configuration & Basic Operation 3-35
The previous SRT-implemented set point is the set point used for calculating the PID constant for the previous
SRT.
In this state, the measurement point is within the ST stable range.
In this state, the change width of the PV every 60 seconds is at the ST stable range or less.
New PID constants are not calculated by Self-Tuning (ST) for the currently
configured set point in the following instances:
• When the PID constants have been changed manually with ST set to
ON.
• When auto-tuning (AT) has been executed.
Self-Tuning (ST) Stable Range
The Self-Tuning (ST) stable range is a mechanism which allows you to
configure the value to determine the condition under which the ST function
occurs.
Table 3.J
At Start of Program Execution
(Self-Tuning ON) When Set Point is Changed
(Self-Tuning ON)
1. The set point at the start of program
execution differs from the set point
when the previous SRT was executed.
2. The difference between the controlled
temperature at start of program
execution and the set point is larger than
both of the following: (proportional
band x 1.27+4
°C) and the ST stable
range.
3. The controlled temperature at the start
of program execution is less than the set
point during reverse operation, and is
greater than the set point during direct
operation.
4. No reset from input error
1. The new set point differs from the set
point used when the previous SRT was
executed.
2. The set point change width is larger than
both of the following: (proportional
band x 1.27+4
°C) and the ST stable
range.
3. During reverse operation, the new set
point is larger than the set point before
the change; and during direct operation,
the new set point is smaller than the set
point before the change.
4. The temperature is in a stable state.
Equilibrium with the output at 0% when
the power is turned ON is also all
right.