St Stable Range - Omron E5CZ User Manual

Determining PID Constants (AT, ST, Manual Setup)
ST
C
25
100
Startup Conditions
1,2,3...

ST Stable Range

Operating Procedure
Advanced Function Setting Level
ST stable
C
st-b
range
1%0
C
st-b
2*0
4. To return to the operation level, press the O key. The temperature dis-
play flashes during self-tuning (ST) execution.
Self-tuning by step response tuning (SRT) is started when the following condi-
tions are met after program execution is started and the set point is changed.
At start of operation
1. The set point at the start of operation
differs from the set point when the pre-
vious SRT was executed. (See note 1.)
2. The difference between the tempera-
ture at the start of operation and the set
point is greater both of the following:
(Present proportional band × 1.27 +
4°C) and the ST stable range.
3. The temperature at the start of opera-
tion is lower than the set point during
reverse operation, and is larger than
the set point during direct operation.
4. There is no reset from input errors.
Note (1) The previous SRT-implemented set point is the set point that was used
for calculating the PID constants for the previous SRT.
(2) In this state, the measurement point is within the ST stable range.
(3) In this state, the change width of the PV every 60 seconds is within the
ST stable range or less.
In the following instances, PID constants are not changed by self-tuning (ST)
for the present set point.
1. When the PID constants have been changed manually with ST set to ON.
2. When auto-tuning (AT) has been executed.
The ST stable range determines the condition under which ST (self-tuning)
functions.
This procedure sets the ST stable range to 20°C..
1. Select the "ST stable range" parameter by pressing the M key in the ad-
vanced function setting level.
2. Use the U key to set the parameter to 20°C.
When set point is changed
1. The new set point differs from the set
point used when the previous SRT was
executed. (See note 1.)
2. The set point change width is greater
both of the following: (Present propor-
tional band × 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 opera-
tion, the new set point is smaller than
the set point before the change.
4. The temperature is stable. (See note
2.) (Equilibrium with the output amount
at 0% when the power is turned ON is
also all right.) (See note 3.)
Section 3-8
45