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Move the sliders and watch the controller react. The process is a typical industrial loop such as a tank level, an oven temperature or a motor speed: it reacts with a delay (dead time) and then settles slowly (time constant).

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What each term does

  • Kp (proportional gain) reacts to the current error. A higher Kp makes the loop faster, but too high makes it overshoot and oscillate. With Kp alone the process value stays below the setpoint: this is the steady-state offset.
  • Ti (integral time) adds up the error over time and removes the offset. A shorter Ti acts more strongly, and too short causes slow oscillations. Set Ti to 0 to switch the integral off.
  • Td (derivative time) reacts to how fast the process value changes and brakes the loop before it overshoots. It’s sensitive to noise, so many real loops run as PI with Td = 0.
The controller uses the standard form CV = Kp × (e + 1/Ti ∫e dt + Td × de/dt), with the output limited to 0–100 %. Like most PLC PID blocks, the derivative acts on the process value instead of the error, so setpoint steps don’t cause a kick, and the integral stops while the output is saturated (anti-windup).

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Tuning rules used

For a process with gain K, time constant τ and dead time θ:
This is a simplified first-order-plus-dead-time model without noise or valve limits beyond 0–100 %. Use the values as a starting point, then fine-tune on the real machine. Siemens PID_Compact and other PLC blocks also have their own auto-tuning.

Analog scaling calculator

Scale the 4–20 mA signal from your transmitter before it goes into the PID.

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