Siemens SIMATIC S7-1200 Function Manual page 21

The controllability of the controlled system can be estimated based on the ratio T
v
max
Process type
I
II
III
Influence of the dead time on the controllability of a controlled system
A controlled system with dead time and recovery reacts as follows to a jump of the output
value.
T
t
T
u
T
g
y
x
The controllability of a self-regulating controlled system with dead time is determined by the
ratio of T
T /T
t
PID control
Function Manual, 03/2017, A5E35300227-AC
/X . Rule:
max
T / T
u g
< 0,1
0.1 to 0.3
> 0,3
Dead time
Delay time
Recovery time
Output value
Process value
to T . T must be small compared to T
t g t
≤ 1
g
2.3 Characteristic values of the control section
Suitability of the controlled system for controlling
can be controlled well
can still be controlled
difficult to control
. Rule:
g
Principles for control
/T , or T ×
u g u
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