Can liquid level relays be used in precise liquid level control applications?

In Figure 1, we can see that the liquid level in the tank has an upper control limit and a lower control limit. The liquid flows out from the solution outlet pipe and flows in from the solution inlet. The liquid level control valve performs the opening and closing of the inlet of the inflow solution.

The liquid level relay is used to control the opening and closing of the electric liquid level control valve. When the liquid level is lower than the lower limit of the liquid level control,The liquid level control valve is opened and the solution is injected into the tank. When the liquid level is higher than the upper limit of the liquid level control, the liquid level control valve is closed, and of course the solution also stops being injected into the tank.

Sometimes, we can also directly control the solution pump, and realize the control of the liquid level of the tank by controlling the start and stop of the pump body.

Water Liquid Level Relay Recommended:

HYCRY8 Series Liquid Level Control Relay

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In Figure 2, we call the deviation between the upper limit of the liquid level control and the lower limit of the liquid level control as the liquid level deviation. Pay attention to the fact that for the liquid level control of the liquid level control valve fully open and fully closed or the pump body start-stop type, the liquid level deviation must take the maximum value, and we call this type of control as position control. The liquid level change of the position control is shown in Figure 2.

We see that the deviation of the bitwise control is large. Especially the negative deviation, because of the existence of the lower limit of the liquid level control, the negative deviation is larger than that seen in Figure 2, and the positive deviation is smaller.

Therefore, it is impossible to accurately control the liquid level by using the water level relay controller to control the liquid level.