What are the electrical methods of level measurement?

What are the electrical methods of level measurement?

Some of the level sensing devices operate by sensing or detecting the differences in the electrical properties, which is created by the interference of the process materials. These properties are capacitance, conductivity, and resistance.
Level measurement by conductivity
The electrical characteristics of the fluids such as dielectric and conductivity are widely used to do the level measurement in a process.

In this type of level measurement, two electrodes are placed in a tank and one of the electrodes is small in length so it won’t be extended to the maximum level while the other electrode is of good length and can be extended to a maximum length. The tank will be grounded and it would act as a common ground. Mostly a stilling well is also used so that the interface is not disturbed and also can prevent the false measurement. So as we can see in the above image the electrode terminals are connected to the relays, and this would transmit the signal to the display or to a control device. If the process level came in contact with any part of the electrode that extends to the minimum level then there could form a conductive path from the grounded tank to the electrode. If the level falls below this electrode, then the path will be interrupted and the gas or vapor would be non-conductive.
This level conduction then would activate a device that would energize a control device so that the pump could be operated, then the system level would automatically be adjusted by the feed controller or other processing equipment. In case if the level rises to a point in which both the electrodes could come in contact with the conductive material then the current will flow through both the electrodes and tank. A relay would be connected to the electrode that is positioned at the maximum level, it will detect the high level and transmit a signal to an alarm or a control device so that it can correct the condition.