SIMATIC PCS 7 PID parameters explained
PCS 7 controllers express proportional action as a dimensionless gain, with integral time (TI) and derivative time (TD) both in seconds. Seconds rather than minutes is worth noting when converting tuning from a system that uses minutes.
The gain-versus-proportional-band question comes up constantly on Siemens systems because the surrounding installed base often uses proportional band. The two are reciprocally related: proportional band as a percentage is one hundred divided by the gain.
Which direction makes the action stronger
On your system a HIGHER proportional number means MORE aggressive proportional action.
Reset is in seconds/repeat, so a LOWER number means FASTER integral action.
This is the single most consequential thing to get right. Proportional band and gain move in opposite directions, and so do repeats-per-time and time-per-repeat. An engineer who has moved from one system to another and carried the old habit across will make loops worse while believing they are improving them.
- Proportional term: gain
- Reset units: seconds/repeat
- Rate units: seconds
- Algorithm form: ideal noninteracting
Gain and proportional band are inverses
A gain of one corresponds to a proportional band of 100%. A gain of two is a band of 50%. A gain of one half is a band of 200%.
The practical consequence is directional: increasing gain makes proportional action stronger, and increasing proportional band makes it weaker. Anyone moving between the two conventions needs that inversion in mind on every single change.
Why the algorithm form matters
The algorithm form matters because the same three numbers behave differently in each. In the series (interacting) form the derivative term multiplies the proportional-plus-integral term, so changing rate also changes the effective gain and reset. In the ideal (non-interacting) form the three terms are independent of each other but all scaled by gain. In the parallel (independent) form even that scaling is absent — gain does not affect integral or derivative action at all. Moving a tuning set between systems without converting for form is one of the commonest ways a loop that worked on one plant fails on another.
Before you change anything
Confirm the units on the actual controller rather than trusting the platform default. Systems get configured in unusual ways, engineering units get changed during a migration, and a controller imported from another site may carry conventions from there.
The fastest check is to make a small deliberate change and watch which way the loop responds. If it gets more aggressive when you expected less, the convention is not what you assumed.
Questions that come up
How do I convert PCS 7 gain to proportional band?
Divide one hundred by the gain to get the proportional band as a percentage, and divide one hundred by the band to go back. The free converter on this site does it in both directions.
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Last reviewed 2026-08-01.