Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Distributive type parameters
Reexamination Certificate
2000-12-11
2003-07-22
Oda, Christine (Department: 2858)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Distributive type parameters
C324S699000, C073S29000R
Reexamination Certificate
active
06597186
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to utilizing controlled transmissions of electromagnetic (EM) energy through or across materials that have previously been barriers to their penetration to determine the fluid level inside a ferromagnetic or non-ferromagnetic tank, and detect the resistivity of the fluid inside the tank.
BACKGROUND OF THE INVENTION
It has long been possible to measure fluid level within a tank by various methods intrusive to the tank. Prior methods and devices have typically measured pressure or electrical conductivity. The prior methods and devices were typically intrusive, requiring holes for guages, windows of differing materials, dismemberment of tanks, etc. Also, the prior methods and devices had great difficulty in taking measurements with respect to ferromagnetic barrier materials. Many of the prior methods and devices cannot function as a single point level sensor for notifying a controller of the presence or lack of fluid. Further, the prior methods and devices cannot function to measure fluid levels non-intrusively over the full range of a tank or vessel. Still further, the prior methods and devices cannot function to measure fluid levels non-intrusively for both ferromagnetic and non-ferromagnetic tanks or vessels. Further, the prior methods and devices cannot function to determine the resistivity within a tank or vessel in order to determine liquid level, location of the liquid/gas interface, or quality determination of the fluid.
It is, therefore, a feature of the present invention to provide a non-intrusive method and device using electromagnetics to creates a metallic transparency in a ferromagnetic material allowing sensing through the ferromagnetic barrier material.
A feature of the present invention is to provide a single point level sensor for notifying a controller of the presence, a change in or the lack of fluid.
Another feature of the present invention is to provide a method and device that can measure fluid level non-intrusively over the full range of a tank or vessel.
Another feature of the present invention is to provide a method and device that can measure fluid level non-intrusively and functions on non-ferromagnetic tanks or vessels.
Yet another feature of the present invention is to provide a method and device that can determine liquid level, location of the liquid/gas interface, or quality determination of the fluid.
Additional features and advantages of the invention will be set forth in part in the description which follows, and in part will become apparent from the description, or may be learned by practice of the invention. The features and advantages of the invention may be realized by means of the combinations and steps particularly pointed out in the appended claims.
SUMMARY OF THE INVENTION
To achieve the foregoing objects, features, and advantages and in accordance with the purpose of the invention as embodied and broadly described herein, a method is provided for creating a non-intrusive device that generates a spectral EM frequency to detect liquid level inside a tank and can identify resistivity within a tank to determine materials in the tank. The present invention applies to both ferromagnetic and non-ferromagnetic tanks. For applications involving ferromagnetic barrier materials, such as, for example, tanks or vessels, the method of the present invention comprises the steps of (a) testing empirically to approximate the conductivity, (b) testing empirically to approximate the permeability, (c) creating a first set of electromagnetic waves adjacent to the material to be measured of a relatively low frequency, (d) impinging the first set of electromagnetic waves on the material for saturating the material, (e) creating a second set of electromagnetic waves having specific constant amplitude of a higher frequency than the first set of electromagnetic waves, the second set of electromagnetic waves for engaging the material and generating a sensing signal having modified characteristics, and (f) receiving the sensing signal through the saturated material such that the modified characteristics of the sensing signal are processed to determine the required information of liquid level and/or liquid type.
Another embodiment of the present invention provides for saturating to a partial level. Saturating to a partial level allows, in a ferromagnetic tank, the signal to both penetrate the tank and travel throughout the tank to utilize the entire tank as a sensing device. At a partial saturation level, the saturation current lowers the magnetic permeability of the ferromagnetic material, e.g., the wall of a tank or the like, enough to allow deeper penetration than expected as well as decreasing the losses of the saturated materials. Therefore, an optimum setting exists that will maximize transfer of electromagnetic energy into the tank walls without forcing excess energy through the tank. In one embodiment of the present invention as applied to non-ferromagnetic tanks, steps “a” through “d” discussed above, are omitted, and, steps e and f transmitted at the appropriate settings provides for electromagnetic penetration of the non-ferromagnetic material. Electromagnetic penetration of the non-ferromagnetic material creates an interaction with the fluid inside the tank. Also, in a non-ferromagnetic level gauge application, the electromagnetic energy is partially transferred into the tank or vessel walls while some energy does penetrate the tank interior. Each embodiment of the present invention can determine a point setting, i.e., trigger the device at a single point, or track incremental changes in level throughout the total height of the tank.
In another embodiment, a method for creating a spectral EM frequency to optimize transfer of energy into a tank by altering the permeability and conductivity is provided. The method comprising the steps of (a) calculating the penetration depth &dgr; using
δ
=
(
1
e
)
L
and
δ
=
1
σ
μ
r
μ
o
f
where
&dgr;=penetration depth,
ƒ=frequency,
&mgr;
r
=relative permeability, and
&mgr;
o
=absolute permeability,
(b) determining the relationship of frequencies such that
ƒ
6
>ƒ
5
>ƒ
4
>ƒ
3
>ƒ
2
>ƒ
1
,
and
(c) using the frequencies to determine the thickness of the material.
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Deb Anjan K.
Em-Tech Sensors LLC
McEwing David
Oda Christine
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