Radar level gauge system

A method for microwave signal based gauging of a distance to a surface with reflective properties at a filling level of a filling material in a tank having at least one interfering structure, comprising:

• transmitting at at least two temporally separated times transmit signals into the tank, and subsequently receiving receive signals including surface echoes;
• recording propagation properties of the transmit and receive signals in association with at least two distinguishable reflective surfaces;
• calculating for each distinguishable reflective surface a difference in the recorded propagation properties between the at least two temporally separated times;
• comparing the calculated differences for the at least two distinguishable reflective surfaces;
• selecting the greatest of said differences as the difference associated with the surface of the filling material;
• and
• determining said distance to the selected surface of the filling material based on propagation properties of transmitted and received signals.

A radar level gauge system for determining a distance to a surface with reflective properties at a filling level of a filling material in a tank having at least one interfering structure, comprising:

• a transmitter for transmitting measuring signals towards the surface of the filling material;
• a receiver for receiving echo signals from the tank;
• a storage for recording propagation properties of the transmit and receive signals in association with at least two distinguishable reflective surfaces;
• processing circuitry for calculating for each distinguishable reflective surface a difference in the recorded propagation properties between at least two temporally separated times, and selecting the greatest of the calculated differences for the at least two distinguishable reflective surfaces as the difference associated with the surface of the filling material, and determining said distance to the selected surface of the filling material based on propagation properties of transmitted and received signals.

A method for microwave signal based determination of a high-level or overfill situation for the filling level of a filling material in a tank having a surface with reflective properties, comprising:

• transmitting at a first time first transmit signals towards the surfaces;
• receiving at essentially said first time first receive signals including a first surface echo;
• recording first propagation properties of the first transmit and receive signals associated with the first surface echo;
• transmitting at a second time second transmit signals towards the surfaces;
• receiving at essentially said second time second receive signals including a second surface echo;
• recording second propagation properties of the second transmit and receive signals associated with the second surface echo;
• wherein the first time and the second time are temporally separated by a first separation time;
• calculating a first difference between the first and second propagation properties;
• determine a distance to the surface of the filling material;