Capacitive level sensors are operated by two electrodes forming a capacitor, often in the form of two parallel metal plates with insulating (non-conductive or “dielectric”) material separating them.
If you’re looking for a level sensor versatile enough to measure liquids, powders or other granular solids, slurries, and more, a capacitive level sensor might be just what you’re looking for.
In the most basic sense, capacitors store electrostatic energy in an electric field. The capacitor’s ability to store this energy (a measurement known as “capacitance”) increases as the voltage is applied to the circuit, and as the volume of insulating material increases.
When functioning as level sensors, capacitors work by processing capacitance with reference to the dielectric constant of the material being measured and the voltage being used to complete the circuit. These measurements are used to determine vessel levels. Higher levels of dielectric material result in greater capacitance, meaning the former can be easily gauged with the latter.
This method of level measurement is sometimes called RF level sense after the radio frequencies applied to the capacitor circuit.
As an example, let’s say that we’re measuring a high-capacitance solution stored within a large metal tank. The two electrodes that form the capacitor will be in the form of a conductive probe like a metal plate, and the vessel wall itself. An RF signal is activated, causing a low current to flow through the solution. This current varies depending on the amount of solution in the tank – a difference that is detected by the capacitor switch and translated into an output suitable for the specific application.
In addition to the wide range of materials and applications capacitive level sensors are capable of performing with, they also have the advantage of being mechanically simple with no moving parts and minimal required maintenance. In addition, they’re well-suited for both point and continuous level measurements and are resistant to agitation.