Patent ID: 7818990

Claim:
An apparatus for determining and/or monitoring at least one process variable of a medium, comprising: a sensor unit; feedback electronics; and supplemental electronics, wherein: said sensor unit, said feedback electronics, and said supplemental electronics form a first oscillatory circuit; said first oscillatory circuit oscillates with at least a resonance frequency (ω 1 ) and/or with a resonance frequency (ω res ) within at least one resonance frequency range; in case of a cable break between said feedback electronics and said sensor unit, said feedback electronics and said supplemental electronics form a second oscillatory circuit; and in case of cable break, said second oscillatory circuit oscillates at a resonance frequency (ω cablebreak ), which differs from the resonance frequency (ω res , ω 1 ) of said first oscillatory circuit; and during normal operation the amplification of said first oscillatory circuit in the range of the resonance frequency or frequencies (ω res , ω 1 ) of said first oscillatory circuit is greater than in the range of the resonance frequency (ω cablebreak ) of said second oscillatory circuit.