Dielectric spectroscopy for measuring the composition of gasoline/water/ethanol mixtures

Dielectric spectroscopy is applied to investigate the feasibility of biofuel composition measurement. Measurements were made on the pure components (ethanol, gasoline and water) and mixtures thereof. Preliminary measurement results indicate that the components have distinguishable spectral dielectric behavior in the ranges 10-100 kHz and 200 MHz-2GHz. A simple linear-mixing algorithm is presented for calculating the composition from two different parameters of the measured data. Measurements show that ethanol concentration is relatively easy to determine by RF impedance measurements of the permittivity of the mixture, provided that the baseline is compensated for the water content. Unambiguous measurement of water content of different types of fuel at low frequencies is still hampered by the salinity of water and the presence of additives (static dissipaters) that lower the conductivity of gasoline.