Patent ID: 8823397

Claim:
A method for determining a level of a material interface in a tank, by means of a radar level gauge system comprising: a transceiver for generating, transmitting and receiving electromagnetic signals; a probe connected to said transceiver and arranged to guide a transmitted electromagnetic signal from said transceiver towards said material interface, said probe comprising a first plurality of reference impedance transitions each located above said material interface at a respective physical distance from a reference position, and a second plurality of reference impedance transitions each located below said material interface at a respective physical distance from said reference position; said method comprising the steps of: determining, for each of said first plurality of reference impedance transitions, a value indicative of an electrical distance along said probe from said reference position to said reference impedance transition based on a received electromagnetic signal reflected by said reference impedance transition, resulting in a first set of electrical distance values; determining, for each of said second plurality of reference impedance transitions, a value indicative of an electrical distance along said probe from said reference position to said reference impedance transition based on a received electromagnetic signal reflected by said reference impedance transition, resulting in a second set of electrical distance values; determining, for said first plurality of reference impedance transitions, a first approximation function relating said first set of electrical distance values to said physical distances; determining, for said second plurality of reference impedance transitions, a second approximation function relating said second set of electrical distance values to said physical distances; determining said level of said material interface based on said first approximation function and said second approximation function.