RF admittance level switches, their measurement principle is: RF admittance is a new level control technology developed from capacitive, which is anti-clogging, more reliable, more accurate, and more versatile, being an upgrade to capacitive level technology. The term "admittance" refers to the reciprocal of impedance in electrical terms, composed of resistive, capacitive, and inductive components. RF, standing for radio frequency, is the spectrum of high-frequency radio waves, thus RF admittance can be understood as measuring admittance using high-frequency radio waves. During operation, the sensor of the instrument forms an admittance value with the container wall and the medium being measured. As the level changes, the admittance value changes accordingly. The circuit unit converts the measured admittance value into a level signal for output, achieving level measurement.