If you’re familiar with the use of floats for monitoring how much fluid is in a container, then you should have a pretty good idea of how a magnetic level transmitter works.
These devices use a small, highly magnetic object suspended in a buoyant float, typically inside a narrow auxiliary column to restrict the float’s lateral movement. The float sits on top of the liquid being measured, and a separate magnetic device tracks the movement of the float so that you can read the current fill level.
This method of monitoring fill level is useful for continuous measurement, as the float will actively rise or sink with the level of liquid in the tank. However, it only works if the auxiliary column, float, and tank are all made of non-magnetic materials.