C135 PCS 7 (PCS7)
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How the PID Terms Shape the Output

# How Integral and Derivative Settings Affect PID Control

A longer integral time makes integral correction slower and weaker; a shorter integral time makes it act faster and more strongly. “Minutes per repeat” expresses the time directly, while “repeats per minute” expresses its reciprocal, so a larger numeric setting has opposite meaning in those two conventions. Derivative action responds to how quickly its input changes; increasing derivative time strengthens that response in time-based PID forms, but can amplify measurement noise. Confirm the exact block and units before changing a PCS 7 loop.

Table of Contents

How the PID Terms Shape the Output

A PID controller combines proportional response to current deviation, integral response to accumulated deviation, and derivative response to the deviation's rate of change. Their contributions depend on the controller structure, scaling, direction, filters and limits. Siemens' standard PID documentation describes integral time as determining the I response and derivative time as determining the D response; the PCS 7 V9.0 training material search record identifies PIDConL parameters GAIN, TI and TD and states the times are in seconds, but that training PDF could not be opened in this verification. Confirm the block-specific manual and engineering units in the installed system before using those names or units.

Integral Time: Minutes per Repeat

In the common time-based convention, TI is integral time (reset time). If the process deviation stays nonzero, the integrator gradually adds correction; increasing TI makes the accumulated correction slower, while decreasing it makes the I action faster and stronger. Stronger I action can remove sustained offset sooner, but can also increase overshoot or oscillation, especially when the actuator saturates or the loop has long dead time. The actual closed-loop result depends on the process and controller implementation.

Integral Rate: Repeats per Minute

Some controllers express integral action as a reset rate in repeats per minute rather than a time per repeat. These parameters are reciprocals when they describe the same convention: reset rate = 1 / reset time in minutes. For example, a time of 2 minutes per repeat corresponds to 0.5 repeats per minute. Thus, increasing minutes per repeat slows integration, whereas increasing repeats per minute speeds it up. Check the controller's unit label and manual; do not transfer a number between these conventions unchanged.

Derivative Time: Response to Change

Derivative action reacts to the rate at which its input changes, so it can counter rapid movement before the accumulated I term catches up. In time-based forms, a larger derivative time generally strengthens this response. Too much D action makes the manipulated output sensitive to fast measurement changes and noise; implementations commonly condition the derivative signal, but filter structure and placement are block-specific. A derivative setting is not a substitute for correcting noisy or faulty measurement signals.

What “MV” Does and Does Not Tell You

MV is the manipulated variable sent toward the controlled process. Changing TI or TD changes a component of the controller calculation, not a guaranteed direction or magnitude of MV movement: response also depends on deviation sign, controller action, gain, other terms, output limits, mode, external tracking and process behavior. Inspect the controller's I and D component outputs where the selected block exposes them, along with PV, SP, error and MV.

A Safe Manual Tuning Approach

  1. Identify the exact controller block, PCS 7/APL/library version, algorithm, parameter units, sample/call time, action direction and operating mode.
  2. Review the loop's PV, SP, deviation, MV, output limits, mode transitions, and any integral or derivative filtering/tracking settings. Confirm instrument scaling and actuator response before tuning.
  3. Use the site-approved tuning method or the tuning function documented for that exact block and version. Change one parameter at a time in an authorized test or controlled operating window; record the original values and maintain a rollback path.
  4. Trend PV, SP, deviation and MV through representative disturbances and setpoint changes. Check whether offset, overshoot, oscillation, noise response and actuator movement meet the process acceptance criteria.
  5. If integral action drives MV against a limit, examine the block's documented anti-reset-windup behavior and loop configuration rather than shortening TI blindly. If D action follows noise, confirm measurement quality and derivative filtering before increasing TD.
  6. Record the final parameter values with their units and the test conditions. Do not infer acceptable operation from a successful compile or from a single transient.

PCS 7 Applicability

The source does not identify the controller block. A PCS 7 loop could use different block families and versions, and their display units, algorithm options, PID tuner availability and parameter semantics must be checked in the matching manual. Siemens' PCS 7 V9.0 training material search result describes PIDConL GAIN, TI and TD in seconds, but the official attachment was inaccessible during this check; this article therefore does not apply that detail as a verified rule to the source loop. The cited opened Siemens V20 PID pages document general S7-300/S7-400 standard PID components and are not a substitute for the project's PCS 7 block documentation.

Verification

Before a change, record the actual block name/version, existing parameter values and units, call/sampling interval, process operating state and loop trends. After a controlled adjustment, compare PV tracking, steady-state offset, overshoot, settling behavior, MV movement and noise response against pre-agreed process criteria. Confirm that the loop remains stable in all required modes and that the parameter is not being overridden by another mode or tracking path. Document the result for the applicable process conditions.

Limitations and Operational Precautions

PID tuning is process-specific. No numerical tuning values or guaranteed response can be selected from the source because it contains no plant dynamics, controller block/version, units, trend data, actuator limits or operating constraints. Derivative and integral behavior can vary with controller structure, filters, execution interval, setpoint weighting and anti-windup implementation. Changes can affect product quality, equipment and process safety; follow site change control and use a qualified, approved tuning procedure.

Engineer FAQ

If TI is shown in seconds, does a larger value make integral action faster? No. In a time-based representation, a larger integral time means slower, weaker integral correction.

If an I parameter is in repeats per minute, does a larger value make I action faster? Yes, for that rate convention. Repeats per minute is the reciprocal of minutes per repeat when both use the same reset definition.

Why can reducing integral time increase overshoot? Faster accumulation can continue driving the output while the process response is delayed or the actuator is limited, increasing the correction beyond what the process needs.

Does more derivative always reduce oscillation? No. Derivative action can oppose rapid changes, but excessive or noisy derivative response can make MV erratic. Its usefulness depends on process dynamics, signal quality and implementation.

Can I tune a PCS 7 PID from the parameter names alone? No. Identify the exact PCS 7/APL block and version, verify units and algorithm in its manual, then use a documented and approved tuning method.

Technical References

  • Siemens, Integral action (S7-300, S7-400) – PID, TIA Portal V20 documentation (11/2024): role of integral time, integral component monitoring, output limits and sampling-time considerations. https://docs.tia.siemens.cloud/r/en-us/v20/using-standard-pid-control-s7-300-s7-400/using-pid_es-s7-300-s7-400/controller-s7-300-s7-400/integral-action-s7-300-s7-400
  • Siemens, Derivative component (S7-300, S7-400) – PID, TIA Portal V20 documentation (11/2024): derivative response to input rate of change, derivative time, filtering delay and implementation constraints. https://docs.tia.siemens.cloud/r/en-us/v20/using-standard-pid-control-s7-300-s7-400/using-pid_es-s7-300-s7-400/controller-s7-300-s7-400/derivative-component-s7-300-s7-400

These references concern Siemens standard PID for S7-300/S7-400 in V20; confirm the matching PCS 7 controller manual before applying block-specific settings.

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Related Tags

PID Control, PCS 7, Integral Time, Derivative Time, Loop Tuning

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