Patent ID: 8432171

Claim:
A method of measuring a concentration of an analyte contained in a sample fluid, wherein at least two capacitive field effect sensors configured in semiconductor technology and having an identical basic structure with a reference electrode are arranged in a shared measuring cell, one of said at least two capacitive field effect sensors forming a measuring sensor with an active transductor layer and another one of said at least two capacitive field effect sensors forming a reference sensor without an active transductor layer, said method comprising the steps of: simultaneously contacting said at least two capacitive field effect sensors with said sample fluid; applying a bias voltage which is composed of an electric DC voltage and a superimposed AC voltage between each capacitive field effect sensor and the reference electrode, said reference electrode being simultaneously contacted by said sample fluid; eliminating any change in capacitance due to the analyte in the sample fluid by controlling said bias voltage applied to said measuring sensor in a closed control loop; and obtaining a measuring signal by calculating a difference between voltage values that are representative of DC voltage potentials applied to said measuring sensor and to said reference sensor, respectively.