Low-cost capacitive sensor for oil-level monitoring in aircraft

Contact capacitive sensors offer good advantages when used in tank level measurement in terms of resolution, allowing for continuous level sensing as opposed to point level one, and construction, well suited to simple and rugged design, implying low production costs and long lifespan. Conventional designs suffer from low sensitivity when liquid involved has a low relative permittivity. Playing with geometrical parameters of the sensor with the aim of increasing its sensitivity usually leads to increase its overall dimensions and weight (per electrode surface widening) or increase viscous resistance to liquid adaptation in the sensor after level changes (per interelectrode gap shortening). A kind of helical electrode pair is here investigated as a hypothesis to increase sensor sensitivity given following added constraints: rugged construction, low overall dimensions and weight, fast measurement (as is needed in aircraft applications), high robustness against mechanical vibrations (as is needed specifically in helicopter applications), with a little higher production cost than conventional sensors of the same category (contact continuous level sensors). That is meant to be an attempt to counteract the said viscous resistance increment with decreasing the gap width. Numerical simulation results are presented showing the possibility of increasing the sensitivity for the allowed gap shortening.