Radar-based method of measuring the level of a material in a container

A radar-based method of measuring the level of a material in a container in which, by means of the antenna of a ranging device arranged above the highest level anticipated, microwaves are radiated downwards and reflected microwaves received, the echo profile representing the amplitude values of the received microwaves as a function of the transit time or the distance corresponding to the transit time is registered, a maximum of the echo profile is determined for detecting the echo blip in the echo profile originating from the echo waves reflected by the material surface and the distance of the material surface from the antenna is obtained from the peak value of this echo blip, wherein on occurrence of a double blip comprising two overlapping echo blips, of which the first echo blip originates from the microwaves reflected by the material surface whilst the second echo blip originates from the microwaves reflected by an interface located just below the material surface and has a larger peak value than the first echo blip, the following method steps are put to use for determining the peak value of the first echo blip:

• A:
• starting from said determined maximum of the echo profile corresponding to the peak value of the double blip the measurement points of the echo profile located in the direction towards smaller distance values are evaluated to determine
• a) the first maximum slope of the echo profile located nearest to said maximum of the echo profile and the corresponding distance value;
• b) the minimum slope of the echo profile located nearest to said first maximum slope and the corresponding distance value;
• c) the second maximum slope of the echo profile located nearest to said minimum slope and the corresponding distance value;
• B:
• the distance value located in the middle between the distance value of said second maximum slope and the distance value of said minimum slope is used as the distance value of the peak value of the first echo blip and the corresponding amplitude value is used as the peak value of the first echo blip to obtain the distance of the material surface from the antenna.