Patent ID: 7415366

Claim:
A field device electronics comprising: a sensor unit for capacitive fill level measurements in a container, wherein the field device electronics is connected over signal paths with said sensor unit, produces a voltage signal for driving said sensor unit, and receives and evaluates a measurement current from said sensor unit; an analog/digital converter a current-/voltage-converter which converts the measurement current, before the evaluation, into a measurement voltage proportional to the measurement current; a rectifier which rectifies the measurement voltage and produces an output voltage; a microprocessor; and a memory unit, wherein: said analog/digital converter digitize said output voltage; said microprocessor performs the production of said voltage signal, the evaluation of the measurement current and a compensation of interference parameters, and a determining of the parameters of the sensor-container arrangement which are to be determined, according to predetermined program routines; and said parameters of said sensor unit-containers arrangement which are to be determined are an impedance and/or a capacitance and/or a conductivity; said program routines for performing of said microprocessor are stored in said memory unit; said microprocessor determines and evaluates the value of the measurement current at a certain phase-shift angle with reference to said voltage signal; said rectifier is a synchronous rectifier; said microprocessor produces a synchronization signal of said synchronous rectifier; said certain phase-shift angle between said voltage signal and said measurement current is set by a phase-shift of said synchronization signal with respect to said voltage signal, which phase-shift is produced by said microprocessor; and depending on the phase-shift angle which has been set, an apparent current measurement or a pure reactive current measurement or a pure active current measurement is performed.