Patent ID: 9746366
Date: 2017-08-29
CPC Classifications: G01F,G01S

Claim:
1. A method for determining a distance to a surface of a product in a tank based on a time delay of electromagnetic signals propagating between a predefined reference and a surface of said product, said method comprising the steps of: i) generating a transmission signal in the form of a first pulse train having a predetermined pulse repetition frequency, said first pulse train comprising at least 5 pulses having a constant pulse repetition frequency; ii) generating a reference signal in the form of a second pulse train by generating a predefined and fixed time delay between said first and second pulse trains relative each other; iii) guiding said transmission signal into the tank as electromagnetic signals, and allowing said signals to propagate towards said surface; iv) receiving a reflected signal reflected from the tank; v) forming a correlation value based on a time correlation between a pulse of the reference signal and the reflected signal, and storing said correlation value and the associated pulse repetition frequency; vi) carrying out steps i) to v) in sequence for at least three different pulse repetition frequencies, until at least three pairs of correlation values and associated pulse repetition frequencies have been stored; vii) determining said distance based on said at least three pairs of correlation values and associated pulse repetition frequencies, and said fixed time delay between the reference signal and the transmission signal.