Patent ID: 8276444

Claim:
A method for ascertaining and monitoring the fill level of a medium in a container by means of a field device using a travel time, the method comprising the steps of: transmitting transmission signals in a direction of the medium and receiving reflection signals; registering the received reflection signals as echo signals in an echo function as a function of travel time or travel distance; ascertaining or predetermining as well as storing in a first measuring cycle, a masking curve, evaluation curves and/or echo parameters of the echo signals in the echo function; ascertaining at least one wanted echo signal in the echo function by means of a static echo search algorithm, through the masking curve, the evaluation curves, the echo parameters, position (x 1 ) and/or amplitude (A 1 ); performing a continuous echo tracking of positional changes and/or of amplitude changes of individual echo signals and/or the wanted echo signal in the echo function by means of a dynamic echo search algorithm; adjusting the masking curve, the evaluation curves and/or the echo parameters of the static echo search algorithm are adjusted on the basis of positional changes and/or amplitude changes of individual wanted echo signals from the echo tracking by the dynamic echo search algorithm; making from the positional changes and the amplitude changes deductions concerning changes in the masking curve, the evaluation curves and the echo parameters; newly calculating or adjusting on the basis of the new positional changes of the echo signals and the wanted echo signal the evaluation curves and the masking curve; and adjusting the static echo search algorithm on the basis of the changes in the masking curve, the evaluation curves and the echo parameters to the changing measuring conditions.