Geisheimer, J., Wabs, M., and Carvalho, C., "Using Time Domain Reflectometry to Measure Fluid Properties for IVHM Applications," SAE Technical Paper 2015-01-2593, 2015, doi:10.4271/2015-01-2593.
Time Domain Reflectometery (TDR) is a Radio Frequency (RF) technology that has been used for many years to find cable breaks and measure fluid levels in industrial processes. The technology uses picosecond length pulses and the associated reflections off the fluid surface in a time of flight measurement to determine fluid height. TDR signals have additional information that can be processed and utilized for Integrated Vehicle Health Management (IVHM) applications. For example, when water collects in the fuel tank, TDR is capable of identifying and measuring the amount of water. This can allow the water sumps to be drained on condition instead of on a schedule. In addition, electromagnetic properties of the fluid can be determined, such as the dielectric constant, which can be used to identify mis-fueling situations, contaminants in the fluid, and potentially other fluid health properties.This paper details the work of the authors in utilizing TDR technology for making advanced measurement of fluid properties for IVHM applications. This includes water and ice measurement in fuel, determining mis-fueling and contaminants, as well as in-situ measurement of other electromagnetic properties of fluids. The results show that TDR technology is suitable for a dual/purpose sensor providing normal fluid level measurement and diagnostics information for IVHM.