US 6,178,817 B2Granted

Material level sensing

AssigneeVenture Measurement

InventorsScott M. Hewelt, Michael C. Torzewski, Norman F. Marsh

Life of this patent

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Abstract

A system for point-level detection of material within a vessel includes a transmission line probe adapted to be mounted to a wall of the vessel so as to extend within the vessel for contact with material when the material reaches a preselected level within the vessel. Electronics are operatively coupled to one end of the probe for launching microwave energy along the probe. The electronics are responsive to a change in microwave energy reflected from the free end of the probe within the vessel when the material is in contact with the probe, employing time-domain reflectometry techniques, for indicating that the material is in contact with the probe. This change in reflected microwave energy may comprise a change in phase or, more preferably, a change in apparent length of the probe resulting from contact with material having a higher dielectric constant than that of air when air surrounds the probe. The electronics preferably are also responsive to a decrease in apparent length of the probe for indicating a failure condition at the transmission line probe or electronics.

A system for measuring level of material in a vessel that comprises:

a transmission line probe adapted to be mounted to a wall of the vessel so as to extend within the vessel for contact with material in the vessel, and
electronic means for operative coupling to one end of said probe, including means for launching microwave energy along said probe and means responsive to energy reflected from said probe employing time domain reflectometry for obtaining a measurement of level of the material in the vessel,
said transmission line probe comprising:
coaxial connection means having a center conductor connected to said electronic means, an outer conductor and a characteristic impedance between said center and outer conductors,
a cylindrical shell of electrically conductive composition separate from said coaxial connection means, including means coupling said coaxial connection means to one end of said shell and electrically connecting said shell to said outer conductor of said coaxial connection means, and means for mounting said transmission line probe to a vessel wall,
an electrically conductive rod extending through said shell coaxially with said shell, said rod being separate from said coaxial connection means, and being electrically connected at a first end to said center conductor of said coaxial connection means and having a second end spaced from said first end,
insulating means disposed between said shell and said rod entirely through said shell electrically insulating said shell from said rod such that said shell, said rod and said electrical insulating means have a characteristic impedance that matches that of said coaxial connection means,
means on said second end of said electrically conductive rod extending from said shell and said insulation means for detachable electrical and mechanical coupling to a probe rod for extending into said vessel, and
a probe rod removably attached to said second end of said electrically conductive rod for contact with material in the vessel.

6 more elements

Facts

Application

08/974,207Filed 19 Nov 1997 · us provisional application

Priority

22 Nov 1996

Granted

30 Jan 2001

Term ends

Not estimatedThe source records don’t support an estimate.

Classification3 codes

G01F 23/284
By measuring the variations of parameters of electromagnetic or acoustic waves applied directly to the liquid or fluent solid material:…
G01F 25/24
Of apparatus for measuring liquid level: testing proper functioning of electronic circuits
G01F
Measuring volume, volume flow, mass flow or liquid level

Abstract

Claims21