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PID control is a very powerful and high quality solution for many control processes. The biggest problem of PID controllers is the tuning of the controller in accordance with the controlled system/parameter. Tuning control is not an easy operation and the controller and controlled system have to permit this. High level instruments offer the auto-tuning of controllers that is oriented to the automation of the controller reaction and do not request common PID tuning.
Linear control is the first solution to on/off control issues. Linear control systems use linear negative feedback to produce a control signal mathematically based on other variables, with a view to maintaining the controlled process within an acceptable operating range. The output from a linear control system into the controlled process may be in the form of a directly variable signal, such as a motorized valve that may be 0 or 100% open or anywhere in between. Sometimes this is not feasible and so after calculating the current required correcitve signal, a linear control system may repeatedly switch an actuator, such as a pump, motor or heater, fully on and then fully off again, regulating the duty cycle inside the time cycle using pulse-width modulation.
"This facility has utilized every conceivable application of the PCA 310 as we did with the PCA 300 and will continue to do with the PCA 320.Utilizing this series of analyzers has enhanced our process control and we anticipate being able to eliminate compliance exceedances.We have been able to reduce consumption of chlorine and minimize impact to the receiving waters. Better for our bottom line and better for the environment."
- Roy Stanton, Washington Water Service Company
Disinfection is a process of killing disease-causing organisms (or pathogens). Chlorine (Cl2) is a very desirable disinfectant because, when mixed with pure water, it reacts to form hypochlorous acid (HOCl) and hydrochloric acid (HCl). HOCl (free active chlorine) is the most effective form of chlorine for disinfection. Read this white paper to find out more about Disinfection and Chlorine.