Siemens Simatic S7 Series System Manual

PID loops and tuning
11.4 Auto-tune sequence
S7-200 SMART
474 System Manual, 09/2015, A5E03822230-AC
Notice how the auto-tuner switches the output to cause the process (as evidenced by the PV
value) to undergo small oscillations. The frequency and the amplitude of the PV oscillations
are indicative of the process gain and natural frequency.
Based upon the information collected about the frequency and gain of the process during the
auto-tune process, the ultimate gain and ultimate frequency values are calculated. From
these values, the suggested values for gain (loop gain), reset (integral time), and rate
(derivative time) are calculated.
Note
Your loop type determines which tuning values are calculated by the auto
-tuner. For
example, for a PI loop, the auto
-tuner will calculate gain and integral time values, but the
suggested derivative time will be 0.0 (no deriv
ative action).
Once the auto-tune sequence has completed, the output of the loop is returned to its initial
value. The next time the loop is executed, the normal PID calculation will be performed.

Siemens Simatic S7 Series Specifications

General

CPU	Varies by model (e.g., S7-300, S7-400, S7-1200, S7-1500)
Communication Interfaces	PROFIBUS, PROFINET, Ethernet, MPI
Programming	TIA Portal, STEP 7
Programming Languages	LAD, FBD, STL, SCL, GRAPH
I/O Modules	Digital, Analog, Specialty modules available
Operating Temperature	0°C to 60°C (standard models)
Mounting	DIN rail mounting
Operating Voltage	24V DC or 120/230V AC (varies by model)
Protection Class	IP20 (standard models)
Memory	Varies depending on the S7 model. Includes work memory (RAM) for program execution, load memory (EEPROM or Flash) for program storage, and system memory for operating system functions. Memory sizes range from kilobytes to megabytes.