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- After you have loaded the proper PID control function and have created the appropriate set points in your method file, set the P, I, and D set points to zero.
- Set P to a small value and change the target value to provoke a response from the PID control.
- Observe the graph of the variable being controlled for this value of P. If the result is an oscillation that becomes damped (decreasing amplitude), increase the value of P incrementally and repeat the process. If the result is an oscillation that becomes amplified (increasing amplitude), lower the value of P and repeat the process.
- The objective is to find a value of P for which there is a periodic oscillation of the value with a constant amplitude. Once this the correct P value (Ku) has been found, write it down and also record the period of the wave (time between two consecutive crests of the oscillation - Pu - in minutes).
AguaClara researchers typically use PI control (the value of D is set to zero). To find the value of P required, use the equation: P = Ku/2.2. To find the value of I required, use the equation: I = Pu/1.2. This should result in a value in minutes, which is the correct unit for I.
Change your set points (P and I) to the new values. Ensure that there is less than 10% variation in your variable, and fine tune if necessary.
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