A float level sensor is a device used to detect the level of liquid in a tank or container. It fundamentally works by utilizing the principle of buoyancy.
The Basic Principle
The core component is a float, which is a hollow or solid object that is less dense than the liquid it is placed in. Because of buoyancy, the float rises and falls with the level of the liquid. The sensor then translates the vertical position of this float into an electrical signal or a mechanical action.
Common Mechanisms
While the basic principle of using a buoyant float is consistent, different mechanisms are used to convert the float's position into a usable output:
Magnet and Reed Switch
One common method involves a float that contains a magnet and a stationary tube or stem that houses one or more reed switches.
- As the liquid level changes, the float moves vertically along the stem.
- When the float's magnet comes near a reed switch, the magnetic field causes the switch contacts to close (or open, depending on the switch type), completing or breaking an electrical circuit.
- As described in the reference, the float's movement can cause it to orient itself, for instance, becoming "more vertical," which in turn causes the magnet inside to "fall down with gravity to either come in contact with the reed or switch away from it," thereby changing the state of the switch.
This method typically provides a simple on/off signal, indicating whether the liquid level is above or below the point where the reed switch is located. Multiple reed switches can be placed at different heights on the stem to detect several discrete levels.
Other Methods
- Mechanical Linkage: Some sensors use mechanical arms or linkages connected to the float that operate a switch or indicator.
- Magnetic Resistance/Inductance: More complex sensors might use a magnetic float moving along a stem that contains resistors or inductors, providing a continuous or stepped electrical signal corresponding to the float's position.
Applications
Float level sensors are versatile and widely used in various applications for simple liquid level detection, such as:
- Turning pumps on or off
- Triggering alarms
- Indicating high or low levels in tanks
In essence, the float acts as a simple indicator of liquid level, and the sensor mechanism converts this physical position into a usable electrical signal or mechanical action, often using a magnet and a reed switch activated by the float's movement.
