Frequency Shift Capacitance Level Sensors

Capacitance level technology uses the electrical characteristics of a capacitor (a device that has the potential to store an electric charge). Typically a capacitor has two conductors or electrodes separated by a layer of a non-conducting material called a dielectric. In capacitive level measurement, the environment (typically the vessel wall) acts as a reference electrode and the sensor probe as a measurement electrode. The dielectric is composed of the vessel contents (and the measurement electrode insulating layer, if insulated).
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As the level of process material in the vessel rises and starts to cover the probe, some of the insulating effect from air changes into that from the material, producing a change in capacitance between the probe and the reference electrode. This capacitance change provides a direct, linear relationship with vessel level.