a detection chamber to which the sample solution is suppliable through a feed channel, and from which the analyzed sample solution is drainable through an outlet channel,

a CMOS-based microchip that comprises a sensor area arranged in the detection chamber and a contact area that is fluid-tightly separated from the detection chamber,

the sensor area of the microchip including an array of functionalized test sites for electrochemically detecting biomolecules in the sample solution, and

each test site in the sensor area being furnished with its own sigma-delta modulator for the analog-to-digital conversion of electrical signals produced at the test sites upon electrochemical detection; each sigma-delta modulator being integrated in the microchip and adapted to output, as a digitalized signal, a bit stream; and

the microchip including a processing circuit for receiving the bit stream output by each sigma-delta modulator and processing the bit stream output according to the principles of sigma-delta technology to provide the processed output signals to contact pads in the contact area.