Process Types - Siemens SIMATIC Manual

Controller Tuning in FB 58 "TCONT_CP"
3.2

Process Types

Process Types
Apart from the process gain GAIN_P, the parameters shown in the schematic
below, lag time TU and process time constant TA are characteristic parameters of
a process.
The schematic below illustrates the step response:
TU
The table below lists the various processes with which you can use
FB 58 "TCONT_CP":
Process Type I
Typical temperature
process (ideal situation)
TU/TA < 0.1
One dominating time
constant
FB 58 "TCONT_CP" is designed for typical temperature control processes of type I.
You can, however, also use the block for higher order processes of type II or III.
3-2
Point of inflection
TA
Process Type II
Intermediate range
TU/TA approx. 0.1
2 approximately
equivalent time
constants
Process responce to a
manipulated variable
step change
t
Process Type III
Higher order temperature
process (high lag)
TU/TA> 0.1
Several time constants
PID Temperature Control
A5E00125039-02