Patent ID: 7423436

Claim:
Capacitive level measurement and detection device for measurement or detection of the level of a medium in a container, comprising: a sensor element, a reference element, the reference element being arranged relative to the sensor element in a manner enabling the medium, the level of which is to be measured or detected, to influence the impedance between the sensor element and the reference element, and an electrical circuit having at least one AC voltage source and an evaluation unit, the evaluation unit being connected to the sensor element and to the reference element, wherein the AC voltage source supplies a high-frequency voltage or a voltage which contains high frequency voltage portions; wherein the electrical circuit further comprises a timer which is connected to the AC voltage source and is adapted to shift the phase of the AC voltage over one period; wherein a pulse shaper is connected downstream of the timer for producing a uniform pulse with the pulse width from the phase-shifted AC voltage; wherein the electrical circuit further comprises a synchronous rectifier, on the input side of which the high frequency or broadband measurement signal and pulses generated by the pulse shaper are supplied; wherein the electrical circuit further comprises a current to voltage I/V converter connected downstream of the synchronous rectifier; wherein the electrical circuit further comprises has a microcontroller connected downstream of the I/V converter; wherein the sensor element, the reference element, the synchronous rectifier and the I/V converter form a measurement branch of the electrical circuit, and where a reference branch is connected in parallel with the measurement branch, the reference branch comprising a reference impedance, a second synchronous rectifier and a second I/V converter, wherein the second synchronous rectifier and the second I/V converter are the same as the synchronous rectifier and the I/V converter of the measurement branch; wherein a reference signal and pulses generated by the pulse shaper are supplied to the input side of synchronous rectifier of the reference branch; and wherein said evaluation unit is comprised of the second synchronous rectifier, the second I/V converter, and said microcontroller.