Level control using PLC
The following diagram shows a level control that can be used in the industry:
Figure 9.49 – Level control
The tank has two level sensors (a high-level sensor and a low-level sensor). The low-level sensor is connected to I0.2, while the high-level sensor is connected to I0.3. A pump connected to Q0.0 via a contactor supplies liquid to the tank. The start push button (normally open) is connected to I0.0, while the stop push button (normally closed) is connected to I0.1. The pump ON indicator is connected to Q0.1. A manual discharge valve is used to discharge the liquid when required.
When the start push button is pressed and released and there is no liquid in the tank, in other words, the low-level sensor cannot detect liquid, the pump should start running until the liquid fills the tank, in other words, the high-level sensor detects liquid.
When the manual discharge valve is opened and the liquid falls below the high...