A basic magnetic level sensor is a device used to measure the level of liquid or granular materials inside a container or tank. It works on the principle of magnetic field detection. The sensor typically consists of two main components: a float and a reed switch.
Float: The float is a small, buoyant object that moves up and down with the liquid or material level in the container. It is usually cylindrical or oblong in shape and contains a magnet or a magnetic element inside it.
Reed switch: The reed switch is an electrical switch that consists of two metal contacts (reeds) inside a sealed glass tube. When a magnetic field is present near the reed switch, the contacts are drawn together, allowing current to flow through the switch. When the magnetic field is removed, the contacts separate, interrupting the current flow.
Operation:
Mounting: The magnetic level sensor is installed on the outside of the container or tank, typically near the top or bottom. The float is placed inside the tank, and the reed switch is positioned outside the tank in proximity to the float's path of movement.
Calibration: Before using the sensor, it must be calibrated to determine the appropriate level values for "empty" and "full" conditions. This calibration sets the position of the reed switch corresponding to these levels.
Level Measurement: As the liquid or material level changes inside the tank, the float moves accordingly. When the float reaches the proximity of the reed switch, the magnetic field from the float's magnet or magnetic element triggers the reed switch. This causes the reed switch contacts to close, completing an electrical circuit.
Signal Output: The closing of the reed switch sends a signal to a control system or display device, indicating the current level of the material in the tank. The control system can then interpret this signal and display the level reading to the user or use it for process control.
Advantages of Magnetic Level Sensors:
Simple and reliable operation.
No direct contact with the liquid or material being measured, making them suitable for corrosive or hazardous substances.
Low maintenance requirements.
Can be used for both point level detection (e.g., detecting when the tank is full or empty) and continuous level measurement.
However, it's essential to note that magnetic level sensors have limitations, such as sensitivity to external magnetic fields and the need for proper calibration to ensure accurate measurements. They are best suited for applications where high precision is not required, and where the conditions are within the sensor's specified range.