PID Tuning Simulator
A live tank with four control loops: level, pressure, temperature and flow. Select a loop, tune Kc, Ti and Td, upset the process and watch the SP, PV and MV trends. Start with a ready-made scenario, or build your own.
How PID control works
Each loop compares the process variable (PV), what the transmitter measures, with the setpoint (SP), where you want it. From the difference (the error) it calculates the manipulated variable (MV): the valve opening.
MV = Kc · [ e + (1/Ti)·∫e dt + Td · de/dt ]
| Term | What it does | Too much | Too little |
|---|---|---|---|
| P: gain Kc | Pushes the valve in proportion to the error, right now. | Overshoot and oscillation; the valve slams, or jitters on noisy loops. | Slow, sluggish response. |
| I: integral time Ti (s) | Keeps moving the valve while any error remains, so it removes the offset. Smaller Ti = stronger integral. Ti = 0 switches it off. | (Ti too small) slow, rolling oscillation and overshoot. | (Ti too large or 0) PV creeps back slowly, or settles with a permanent offset. |
| D: derivative time Td (s) | Reacts to how fast PV is changing and brakes early. Helps slow loops with lag, like temperature. | Amplifies sensor noise; a jittery valve. | More overshoot on slow, lagging loops. |
Four different loops
- Flow (FIC-104) is fast and noisy: low gain, short Ti, no derivative.
- Level (LIC-101) is integrating here, because the outflow is held by the flow controller. It needs integral action, gently.
- Pressure (PIC-102) is moderately fast and direct acting: pressure above SP opens the vent.
- Temperature (TIC-103) is slow, with jacket lag and dead time. That's where derivative helps.
Use your own units and real fluctuations
Open Units, range & PV fluctuation on any loop's faceplate. Pick your unit (psig, bar g, kPa, inH₂O, °F, gpm, kg/h…), enter your transmitter's range, and describe the swing you see on site, for example pressure swinging between 510 and 524 psig every 30 s. In MAN the PV follows that band; in AUTO a live readout tells you how much your tuning reduces it, or if it makes it worse. Save the whole setup as a named scenario to replay later. The "Pressure swings 510–524 psig" scenario shows the idea step by step.
Things to try
- Select the level loop, set Ti to 0 (P only) and lower the feed supply pressure. The level settles below SP: that's offset. Set Ti to 60 s and watch it disappear.
- Raise the level Kc to 15 and change its SP. The valve swings open and shut, and the pressure swings with it as liquid compresses the gas blanket.
- Turn on sensor noise and set the flow Kc to 4. The flow valve jitters. That's why flow loops use low gain.
- Put the pressure controller in MAN, close the vent to 5 % and watch the relief valve lift. Switch back to AUTO: the transfer is bumpless.
This simulator is a teaching model. The tuning that works here won't transfer directly to a real plant, but the behaviour you see does. Read more in Control Systems.