Siemens SIMATIC S5 Manual page 86

Description of the Firmware
Fig. 1.2.2/1 shows a typical temperature curve during a heating process with a 2-step controller,
for which the self-tuning function performs a process identification. From the data of the process
identification, the self-tuning function determines the optimum controller parameters. During this
heating procedure, overshoot up to 8 C can occur.
Fig. 1.2.2/2 shows a heating process with the same controlled system as shown in Fig. 1.2.2/1. The
controller operates with the parameters determined by the self-tuning function for this system.
Fig. 1.2.2/3 shows a temperature curve during a heating process with a 3-step controller in which
the self-tuning function performs the process identification. During the heating process, the
self-tuning function switches the cooling on in addition to the heating to determine the ratio of the
heating and cooling actions. It is possible at times for the cooling function to operate alone.
Fig. 1.2.2/1 Heating process with self-tuning function (2-step controller) while determining parameters
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IP244
C79000–B8576–C860–02