Schneider Modicon PID parameters explained
Schneider Modicon controllers — M340, M580 and the Quantum line — express the PID terms as a proportional gain with integral time and derivative time in seconds. The convention matches most modern systems: higher gain is stronger, higher integral time is slower.
Seconds rather than minutes is the detail to watch when a tuning set arrives from a minutes-based plant, and the inversion between gain and proportional band matters for anyone arriving from the Foxboro side of the family.
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
The two conventions in one family
Schneider spans the Modicon PLC line and the Foxboro process systems, and the two do not share a convention: the process systems commonly use proportional band with reset in minutes per repeat, while the Modicon controllers use gain with times in seconds.
On a site that runs both, the same nominal tuning set can mean opposite things in the two worlds. The direction of a change flips with the units, so the habit that works on one will invert on the other.
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
Is Schneider reset in seconds or minutes?
Seconds is the common configuration on Modicon M340, M580 and Quantum. Foxboro process systems in the same family use minutes per repeat, so confirm which world a controller belongs to before reading a number.
Does a higher Schneider gain mean more aggressive action?
Yes — gain is the direct multiplier on error. A higher number is more aggressive, which is the opposite of a proportional-band system.
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Last reviewed 2026-08-01.