Broad-band dielectric spectroscopy of low-permittivity fluids using one measurement cell

Dielectric spectroscopy is a relevant method for quality characterization of petrochemical products, provided that the permittivity spectra are measured with high precision over a broad frequency range. This paper describes how the permittivity of low-loss liquids such as crude oils can be measured with high precision using a single measurement cell in the broad frequency range 1 kHz to 6 GHz. The use of a single cell ensures that the whole dielectric spectrum is measured under the same conditions, which is an advantage for both on-line and laboratory applications. The permittivity spectrum is obtained by combining impedance and S-parameter measurements of a coaxial transmission/reflection cell with suitable permittivity calculation methods. The high sensitivity of the system is confirmed by measurements on crude oils and known low-loss liquids.