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Title: High accuracy electronic material level sensor

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%.
Inventors:
 [1]
  1. (Livermore, CA)
Issue Date:
OSTI Identifier:
870863
Assignee:
Regents of University of California (Oakland, CA) LLNL
Patent Number(s):
US 5610611
Contract Number:
W-7405-ENG-48
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Country of Publication:
United States
Language:
English
Subject:
accuracy; electronic; material; level; sensor; dipstick; based; time; domain; reflectometry; tdr; electrical; pulses; propagated; transmission; line; guide; wire; partially; immersed; measured; launcher; plate; positioned; beginning; reflected; produced; interface; due; change; dielectric; constant; difference; reflections; determine; improved; performance; obtained; incorporation; base; referenced; quartz; crystal; ultrawideband; directional; sampler; allow; operation; interconnect; cable; electronics; module; fraction; discriminators; cfds; accurate; measurements; regardless; constants; reduce; eliminate; errors; induced; triple-transit; ghost; improvements; accurate measurements; reflected pulses; guide wire; dielectric constants; material level; domain reflectometry; improved performance; level sensor; dielectric constant; transmission line; electrical pulses; quartz crystal; accurate measurement; time domain; sensor based; partially immersed; time difference; electrical pulse; interface due; reflected pulse; eliminate errors; errors induced; directional sampler; electronic material; accurate measure; rate measurements; accuracy electronic; /342/73/