Patent ID: 7436100
Filing Date: 2008-10-14
Classification: G01F,G01N

Abstract:
1. An apparatus for monitoring a predetermined fill level and/or for determining the density or viscosity of a medium in a container, comprising: an oscillatable unit; a driver/receiver unit; feedback electronics; a microprocessor; and an evaluation unit, wherein: said oscillatable unit is placed according to one of the following: at the height of the predetermined fill level, or such that it reaches to a defined immersion depth into the medium; said driver/receiver unit excites said oscillatable unit to oscillate with a predetermined oscillation frequency via said feedback electronics; said evaluation unit detects the reaching of the predetermined fill level on the basis of a frequency change and/or an amplitude change of the oscillation of said oscillatable unit or determines the density or the viscosity of the medium on the basis of a change of the oscillation of the oscillatable unit, in said oscillation circuit, formed of said oscillatable unit and said feedback electronics; said microprocessor corrects the phase of said feedback electronics over a predetermined frequency bandwidth in such a manner that the sum of the phases of said feedback electronics and said microprocessor follows a predetermined function f(v); said feedback electronics provides said microprocessor with a periodic, rectangular, input signal, which is used by said microprocessor for determining a correction value for the phase; said microprocessor evaluates and further processes the signal delivered from said feedback electronics in the time domain; said microprocessor determines in a first step, on the basis of the edges of the rectangular input signal (In), the frequency of said oscillation circuit; said microprocessor determines in a second step the phase correction value associated with the determined frequency; and said microprocessor issues an output signal with the corrected phase determined in the second step.