Patent ID: 8159386
Filing Date: 2012-04-17
Classification: G01F

Abstract:
1. A method for ascertaining and monitoring fill level of a medium in a container by means of a field device by a travel time measuring method, comprising the steps of: transmitting transmission signals in the direction of the medium and receiving reflection signals said, received reflection signals are registered as echo signals in an echo function dependent on travel time or travel distance; ascertaining, by means of an echo search algorithm, position and/or amplitude at least of a wanted echo signal in the echo function; performing continuous echo tracking of changes of position and/or of changes of amplitude of the wanted echo signal in the echo function in a defined search window; maintaining said position and/or amplitude of said at least said wanted echo signal, in case no wanted echo signal is ascertained in said search window; ascertaining fill level from said position and/or amplitude of said at least said wanted echo signal; and outputting a measured value of the fill level, wherein: said position and/or said amplitude of said at least said wanted echo signal is maintained at least for a predetermined delay time, after expiration of a predetermined delay time, the width of said search window is set with at least one predetermined slope, and said slope is asymmetrically set from an inflow velocity and/or from an outflow velocity.