Hand-held unit for liquid-type recognition, based on interdigital capacitor

The implementation of a unit capable to recognize liquids based on an interdigital capacitive sensor (IDC) is presented. The sensor's structure was fabricated on standard FR-4 PCB board. Its capacitance change relies upon permittivity change of the medium above IDC electrodes, representing dielectric properties of the liquid used. Along with the microcontroller and simple interface circuit, information about the type of the liquid is presented on a 2 × 16 character display and through RS232 connection on PC. Implemented unit was tested against seven liquids (benzene, phenol, acetone, ethanol, methanol, formaldehyde and distillated water) and a steady state when unit only detected air. Results imply usage of this approach for the fabrication of cost effective, portable devices for on-field sensing applications.