Update on Non-Electrically Invasive Liquid Level Measurement

Unexplained aircraft losses, which may have been caused by electrical equipment inside the fuel tank initiating an explosion, have prompted the development of an electrically isolated Fuel Quantity Indicating System (FQIS). A liquid level transducer utilizing anisotropic magnetoresistance properties to measure the quantity of fuel in a tank with no electrical items or electrical power in contact with the liquid fuel inside the tank was introduced in April 2002 at the Society of Automotive Engineers, General Aviation Technical Conference 2002, in Wichita, Kansas. A magnetoresistive sensor measures the angle of a magnetic field that rotates as a function of the position of a float, thus indicating the quantity of fuel in the tank. More than a laboratory curiosity, this transducer has been continuously developed to make it more reliable, easier to produce, and thus less costly. This paper provides an update to the original paper, 02GAA-7, Non-Electrically Invasive Liquid Level Measurement, discussing design improvements, installation requirements, and installation data. Additional applications such as quantity measurement of potable water, quantity measurement of conductive liquids, and non-contacting position transducers are discussed.