Level Controller Principle - Introduction

The core principle of the liquid level controller is to detect changes in liquid level through sensors, convert them into electrical signals, compare the set values with the controller, and drive actuators such as pumps/valves to achieve automatic liquid level stability and over limit alarm.
Mainstream types and principles
-Floating ball type (common standard): The floating ball rises and falls with the liquid level, driving the magnetic ring to trigger the reed switch/micro switch; High position pump stop and low position pump start, with a simple structure and low cost, suitable for water tanks/sewage tanks.
-Electrode type: Utilizing the conductivity of liquid, the circuit conducts when the electrode contacts the liquid, and the liquid level is determined; Mostly used for conductive liquids (water, sewage).
-Capacitive type: The probe forms a capacitance with the container wall, and the change in liquid level changes the dielectric constant and capacitance value, converting the liquid level; Suitable for non-conductive media such as oil and organic solvents.
-Ultrasonic type: The probe emits ultrasonic waves, receives reflected waves from the liquid surface, and calculates the distance based on the time difference; Non contact measurement, suitable for corrosive/high-temperature liquid, avoid foam/steam.
-Pressure type: Measure the static pressure at the bottom of the tank (P=ρ gh) and convert it to liquid level; Suitable for sealed tanks and mixing conditions, requiring compensation for density changes.
Control Logic
- Switch control (commonly used) : Set high and low limit positions; The liquid level reaches high level → stop the pump/close the valve , drop to low level → start the pump/open the valve , and maintain the stability of the interval.
-Continuous control: PID adjustment, precise and stable liquid level at the set point, commonly used in fine chemical processes.
- Alarm protection : Over high and low limit triggers sound and light alarm or interlock shutdown, preventing overflow/dry pumping.

PREV：No previous article
NEXT：Standard configuration: Dry single disc friction clutch

Interested in cooperation or have questions?