High-Resolution Concentration Measurement In Water/N-Butanol Binary System By Means Of High-Frequency Electrical Impedance Method

Chemical composition measurement technologies for binary systems are needed in many industrial and research applications for monitoring fluid composition in pipes and sample analysis. Except for spectroscopy technology, composition measurement is retrieved by monitoring fluid properties as refractive index, density, electrical conductivity or fluid sound velocity. Demanding applications are those where optical access to the fluid is not easy or available, very local or/and fast measurements are required, and where space limitations dictate the use of sub-millimeter non-intrusive sensors. Combination of all the above constraints in one application makes it extremely difficult to cope with. The latter is the motivation for the present work where a novel diagnostic method, based on I-VED (In-Vivo Embolic Detector) patented technology used in humans for the diagnosis of Coronary Artery Disease and Decompression Sickness, is implemented to determine the concentration of a binary mixture using high frequency impedance measurements. At first, the technology allows tuning over a range of excitation frequencies to identify a proper signal where the fluid attains chiefly an ohmic behavior. Then it retrieves chemical composition of the binary system through calibration curves with respect to resistance and temperature. Adaptation of the I-VED as concentration sensor has been driven by the necessity to integrate such a diagnostic in setups where available solutions in literature cannot be applied. Further to satisfying the aforementioned constraints, I-VED offers also other advantages compared to existing technologies as it provides highscale resolution, it is not sensitive to electromagnetic interference (EMI) and it retrieves an integrated signal of the liquid between the electrodes, so localization of the measuring volume can be controlled. The proposed method has been tested in aqueous solutions of alcohol and its dependence on temperature and alcohol concentration has been investigated at an existing experimental setup named SELENE (SELf-rewetting fluid for ENErgy management), developed for heat transfer research applications.