WO2002033364A1

WO2002033364A1 - Gauge comprising a magneto-resistive sensor, for liquid level remote measuring system on reservoirs

Info

Publication number: WO2002033364A1
Application number: PCT/PT2000/000011
Authority: WO
Inventors: José Basílos Portas Salgado SIMÕES
Original assignee: Isa - Instrumentação E Sistemas De Automação, Lda
Priority date: 2000-10-16
Filing date: 2000-10-16
Publication date: 2002-04-25
Also published as: EP1327123A1

Abstract

The present invention, consists in a gauge, that attached to the coupling surface for liquid measuring instruments (1), which is positioned on the upper and outer part of a liquid reservoir, (2), normally used for fuel or other liquid storage, can convert in an electric signal remotely transmitted, the information related to the liquid level inside the reservoir. The reservoir itself, already contains a complementary measuring device composed by a buoy and magnet mechanism, (2, 6). This gauge embodies (magneto-resitive' type-'GMR' effect based sensors, (7) used to determine the direction of the magnetic field through insensitive to the intensity of this one provoked by the rotation of a magnet, (5, 10), within that reservoir, (2).

Description

"Gauge comprising a maαneto-resistive sensor, for liquid level remote measuring system on reservoirs"

Description

Technical Field of the invention

The present invention refers to a measuring instrument (or a gauge), (Fig.1) and (Fig.2), used for distance/remote determinations of the volume level of liquids or fluids stored in liquid reservoirs or deposits, that can have several applications. One of these applications may be the production, storage or fuel ditsribution in its liquid state, at an Industrial and/or Commercial Scale.

Technical Background of the invention

1) The present invention relates to liquid level measuring instruments. A common type of instrument/ measuring sensor is the buoy / float system. This system introduces as a "sensor" element, in the first place, a buoy that floats in the surface of the liquid to be measured. Connected to this buoy we can normally find other moving pieces/arms, that perform in sinchrony between that buoy's oscillations and the liquid level oscillations. In the top of a beam connected to the buoy mechanism there is a magnet, that moves vertically and in rotation over its own axis, provoking a variation in the direction of the magnetic field.

2) Such variation is precepted and visualized by other known devices that contain within itselves, another magnet that acts in sinchrony with the movement of the magnet placed within the reservoir, serving, with the aid of a pointer connected to it, over a visible scale, to indicate the liquid level inside the reservoir. Such already known devices, are usually attached in coupling surfaces, already available in the referred reservoirs.

3) These already known devices, meet some disadvantages: They are composed by mobile and fragile contact pieces, to make the liquid level measuring, as well as comprising the existence of easily breakable /disalignable pointers, which turn them very dependent of calibrations and readjustments; They only make possible the localized measuring, except when connected with or configured to receive a potenciometer to make remote transmissions of the measured signal; This form of configuration, with the potenciometer, presents, beyond constant needs of calibration and adjustment, other failabilities and frailties natural of its own technology.

4) The application of magneto-resistive sensors, is ideal for all types of contactless position (Like for example: Distance, speed, annular speed and sense of rotation) and for energy and electrical current measuring. These sensors ensure a functional reliability, by being permanently stable and without contact with other measuring parts. They can ensure such reliability, even under the worst climate and geophysical conditions, such as rain, dirt, high and low temperatures. These demonstrated capabilities prove the high importance and interest in the use of magneto-resistive sensors, in several industrial applications

Detailed description of the invention

The Gauge illustrated in the drawings, consists in a gauge, (Fig.1), that attached by the already existing means, to the. coupling surface for liquid measuring instruments, [1], which is positioned on the upper and outer part of a liquid reservoir, [2], normally used for fuel or other liquid storage, (Fig.2), can convert in an electric signal remotely transmitted, the information related to the liquid level inside the reservoir, [2]. Such information is given by a buoy,[4] that in synchrony with its fluctuation movement, induces a magnet,[5], positioned in the top of a beam, to turn. This beam is linked to a moving buoy mechanism,[4] and [6], placed within the reservoir wall, [2].

This Gauge (Fig.1) uses "magneto-resistive" type-"GMR- Giant Magneto Resistive"-effect based sensors, [7], embodied in a resin or any other plastic material, according to the illustrated configuration, [7 a]. Those sensors, which positioned on the exterior part of a reservoir [9], are used to determine the direction of the magnetic field, provoked by the rotation of magnet [5] e [10] within that reservoir [2].

In order to avoid calibrations and dependencies with distance, are used sensors,[7] that only measure the direction of the magnetic field, independently from its intensity, which makes the use and assembly of the gauge extremely simple.

This sensor's insensitivity to the intensity of the field, permits that according to this conception, it still can be possible to place over this instrument, another already known localised measuring instrument, which contains another magnet which movement, will also be synchronised with that magnet placed within the reservoir. This movement will cause to move a pointer over a scale, providing the needed local visualisation.

This sensor will demonstratively determine the changes of the magnetic field direction up to a 180.° variation gamma. However, to ensure, in any instant, the faithfull determination of the field direction in a variation gamma above 180.°, the gauge may also use two crossed magneto-resistive sensors, positioned according to an 90.° angle.

The calculation of the field direction from the sensor's (or both sensors) resistence variation is made by a microcontroller with two analogic entries.

Through the resource of appropriate algorithms or a chart, (pre-defined or established during calibration/adaptation to a new reservoir), the same microcontroller may convert the measured angle in the correct percentage volume of liquid in the reservoir (then adapting to the geometry of this one).

The transformation of this digital information in an electric signal due to be transmitted remotely, can be made by any of the conventional means and namely by tension cable or current, by infrared, radio wave and others. The functioning of this invention is protected / isolated from contacts and frictions with mobile parts, from component dislocations and oxidation. This helps it to become at the same time, more reliable, precise, with low maintenance costs and with greater utility and durability for distance verifications.

Claims

1) An instrument for measuring liquid volume levels, comprising a gauge, (Fig.1), composed by a resin or other plastic material, [7a], to be positioned by the already existing means, over the coupling surface for liquid measuring instruments, on reservoirs;

2) Gauge designed to be able to support above.[9], an already existent, local measuring instrument (for example: Instrument with pointer and a scale), without interference of the gauge in that same instrument;

3) Gauge containing within, a magneto-resistive sensor, [7a,], which will detect the direction changes of the magnetic field, provoked by the rotation of magnet [5] e [10], positioned in the top of a measuring mechanism already within that reservoir [2];

4) According to claim 3) the detection of such changes will be conducted by a condutor,(Fig.1)and[9], to a microcontroller with two analogic entries. Through the resource of appropriate algorithms or a chart, (pre-defined or established during calibration/adaptation to a new reservoir), the same microcontroller may convert the measured angle in the correct percentage volume of liquid in the reservoir (then adapting to the geometry of this one);

5)According to claim 3) the digital information provided by the sensor in connection with the microcontroller, will be converted in an electric signal due to be transmitted at distance, for remote measuring. This signal may be transmitted by any of the conventional means (infrared, radio wave, wires, etc.);

6)According to claims 1) and 2), the gauge, contains an embodied magneto- resistive sensor, in a permanently stable position,(Fig.1)and [7], by without contact with other mobile parts, resistent to frictions, oxidation and precision losses;

7)According to claim 3), this sensor will demonstratively determine the changes of the magnetic field direction up to a 180.° variation gamma. However, to ensure, in any instant, the faithfull determination of the field direction in a variation gamma above 180.°, the gauge may also use two crossed magneto-resistive sensors, positioned according to an 90.° angle.