Switched vs. PID Operation: Water Level and Pressure Over Time

摘要

Temporary pumping applica tions present challenges in control and reliability that can be neutralized using a variety of control methods. These applications typically involve either fluid level or pressure control, utilizing an analog transducer or mechanical switches. For level control applications, the sim plest method of operation uses one float switch to start the pump and another to stop it. Each float switch provides a dry contact that allows voltage to pass through to the pump controller. If there is enough storage area for proper operation, this can be a reliable solution; however there is no way to vary the pump speed. Instead, floats must be placed far enough apart vertically to ensure sufficient pump cycle time. This is useful in applications such as sewer or pump station bypasses, but applications such as clarifiers and set tling tanks require a control method that can maintain a steady fluid level.