An impedance limit switch is configured to determine a limit level of a medium. The switch may include a measuring probe having an oscillator circuit; and an electronic circuit configured to generate an excitation signal for the oscillator circuit. The electronic circuit is further configured to sweep a frequency of the excitation signal and determine a resonance curve of the oscillator circuit. The electronic circuit is further configured to adapt an amplitude of the excitation signal dependent upon the resonance curve in order to reduce an EMC radiation of the switch.