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High accuracy electronic material level sensor

United States Patent

*** EXPIRED ***
March 11, 1997
View the Complete Patent at the US Patent & Trademark Office
Lawrence Livermore National Laboratory - Visit the Industrial Partnerships Office Website
The High Accuracy Electronic Material Level Sensor (electronic dipstick) is a sensor based on time domain reflectometry (TDR) of very short electrical pulses. Pulses are propagated along a transmission line or guide wire that is partially immersed in the material being measured; a launcher plate is positioned at the beginning of the guide wire. Reflected pulses are produced at the material interface due to the change in dielectric constant. The time difference of the reflections at the launcher plate and at the material interface are used to determine the material level. Improved performance is obtained by the incorporation of: 1) a high accuracy time base that is referenced to a quartz crystal, 2) an ultrawideband directional sampler to allow operation without an interconnect cable between the electronics module and the guide wire, 3) constant fraction discriminators (CFDs) that allow accurate measurements regardless of material dielectric constants, and reduce or eliminate errors induced by triple-transit or "ghost" reflections on the interconnect cable. These improvements make the dipstick accurate to better than 0.1%.
McEwan; Thomas E. (Livermore, CA)
The Regents of the University of California (Oakland, CA)
08/ 510,980
August 3, 1995
The United States Government has rights in this invention pursuant to Contract No. W-7405-ENG-48 between the United States Department of Energy and the University of California for the operation of Lawrence Livermore National Laboratory.