Patent ID: 8660803

Claim:
A method for detecting a substance comprising: disposing at least one conductive surface to define a space; disposing two or more wire loops within the space adjacent the conductive surface; driving the wire loops with a first radio frequency signal generated by a radio frequency transmitter such that frequency of the first radio frequency varies over time from a first start time to a first stop time, thereby creating a time varying electromagnetic field within the space; receiving emissions as a result of stimulating the space with the first signal, and storing information corresponding to the received emissions resulting thereby as a set of reference points, V EMPTY , taken from the first start time to the first stop time; placing a substance within the space; driving the wire loops with a second radio frequency signal generated by a radio frequency transmitted such that frequency of the second radio frequency signal varies over time from a second start time to a second stop time, to thereby create a time varying electromagnetic field within the space, the time varying electromagnetic field thereby stimulating nuclear quadrupole resonance in the substance located in the space; receiving emissions as a result of stimulating the substance with the second signal and storing information corresponding to the received emissions as a set of signal points, V SIG , taken from the second start time to the second stop time; processing the set of reference points V EMPTY to determine a start point and stop point of a reference curve, L EMPTY representative of the received emissions from the space when empty; and processing the set of signal points V SIG to determine a start point and stop point of a signal curve, L SIG , representative of the received emissions when the space is occupied by the substance, wherein the frequency variation over time in the first radio frequency signals results in receiving a set of detected reference points V EMPTY that have a magnitude and phase that are spread across a complex valued plane, and the reference curve, L EMPTY is determined by selecting representative end points of the set of reference points V EMPTY , and the frequency variation over time in the second radio frequency signal results in receiving a set of detected signal points V SIG that have a magnitude and phase that are spread across a complex valued plane, and the signal curve, L SIG is determined by selecting representative end points of the set of signal points V SIG .