Patent ID: 7839134

Claim:
A method of detecting a size and concentration of an ionic material, the method comprising: measuring voltage drop values of at least three kinds of ionic materials of which sizes and concentrations are known, the measuring voltage drop values including using each of at least two FET-based sensors having different electrical characteristics for detecting ionic materials; determining at least three points in a three-dimensional plot including a size, a concentration and a voltage drop value from the known sizes, concentrations, and the measured voltage drop values of the at least three kinds of ionic materials with respect to the each of at least the two FET-based sensors having different electrical characteristics for detecting ionic materials; approximating the at least three determined points to a single plane with respect to the each of at least two FET-based sensors having different electrical characteristics for detecting the ionic materials; measuring a voltage drop value of an ionic material of which size and concentration are unknown, the measuring a voltage drop value including using the each of at least two FET-based sensors having different electrical characteristics for detecting the ionic materials; determining equipotential lines existing on the plane using the voltage drop value of unknown ionic material with respect to the each of at least two FET-based sensors having different electrical characteristics for detecting the ionic materials; and determining at least one cross point between the determined equipotential lines.