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Here’s what the terms on the PID controller screen above mean:

1. Kp (Proportional Gain) – This determines how strongly the controller reacts to the difference between the setpoint and the actual value (error). A higher Kp increases the control output response but can lead to instability if too high.
2. I-time (Integral Time) – This sets how quickly the controller accumulates past errors and applies corrections. A shorter I-time means faster correction of steady-state errors, but too small a value can cause overshooting.
3. Dead Band – This is a range around the setpoint where the controller does not take action. It helps prevent unnecessary small adjustments when the process variable fluctuates slightly around the setpoint.
4. S-time (Sampling Time) – This defines how often the controller reads the process variable and updates its control output. A shorter S-time leads to more frequent adjustments but may also increase sensitivity to noise.
5. distur. var. (Disturbance Variable) – This represents the impact of external disturbances on the system. It is typically used in advanced control strategies to compensate for unexpected changes in the process.

General PID Tuning Approach

1. Increase Kp until you see oscillations, then back off slightly.
2. Reduce I-time to improve steady-state accuracy but avoid overshooting.
3. Introduce a small dead band if fluctuations become excessive.
4. Adjust S-time if needed to balance response speed and noise filtering.
5. Distur. var. if set to 0%, the controller does not account for disturbances. If increased, the controller becomes more responsive to sudden changes, which can help stabilize the process when disturbances affect the setpoint.

Recommendations for PID Tuning

1. Kp
   • If your system responds too sluggishly, try increasing Kp slightly
   • If the system oscillates or overshoots the setpoint, reduce Kp slightly
2. I-time
   • This is how fast the system eliminates steady-state errors.
   • If there is a slow drift toward the setpoint, reduce I-time for quicker corrections.
   • If there is overshooting, increase I-time to slow down corrections.
3. Dead Band
   • If it’s set to zero, the controller will be constantly adjusting, which may cause unnecessary small corrections.
   • If the system is too sensitive and fluctuates around the setpoint, try setting a small dead band to reduce unnecessary adjustments.
4. S-time
   • A shorter S-time makes the controller react quickly but may also cause unnecessary noise sensitivity.
   • If the process is stable, keep it low otherwise,
   • If the system appears jittery, try increasing S-time to smooth out responses.
5. distur. var.
   • If your process experiences sudden fluctuations (e.g., due to inconsistent ingredient flow or temperature changes), try gradually increasing the disturbance variable to see if stability improves.
   • If the system is already stable, leave it at 0% to avoid unnecessary sensitivity.