Measuring probe

Details Measuring probe Measuring probe

1993-04-22

1995-05-16

Cuchlinski, Jr., William A.

Measuring and testing

Liquid level or depth gauge

Immersible electrode type

G01F 2324

Patent

active

054150426

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

This invention concerns a measuring probe to detect the presence at the site of the probe of electrically conducting material in granular or liquid form.


SUMMARY OF THE INVENTION

The probe can be used to provide an electrical signal to indicate that electrically conducting material in granular or liquid form is at least present at the level of the probe. Such a signal can be used as an indication of how much granular or liquid material is in a container in which the probe is disposed at a given height above a lower part of the container.
According to the invention a measuring probe to detect the presence at the site of the probe of electrically conducting material in granular or liquid form comprises a first electrode and a second electrode spaced from said first electrode, and means whereby the first and second electrodes can be connected to a supply of electrical energy so that when a space between said electrodes is electrically bridged by the electrically conducting material an electrical circuit through the probe is completed, characterised by said first electrode being spaced from said second electrode by electrically insulating porous gas permeable material, and means whereby gas can be propelled through said gas permeable material between the electrodes outwardly from the probe to pass through said space.
In the event of a bulk volume of electrically conducting granular material dropping below the level of the probe, that bulk volume may leave behind it threads or lumps of adhering granular material also sticking to both the electrodes to provide an electrically conducting residual bridge therebetween. The existence of such a residual bridge may result in a spurious signal appearing in an electrical circuit connected to the electrodes to wrongly indicate that the bulk of the material is still level with the probe. Flow of gas from the probe can be of sufficient force to blow away any such residual bridges, and thus the probe can be self-cleaning. In the case where the probe is being used to detect the presence or otherwise of electrically conducting liquid at the level of the probe then should the level of the liquid drop below the electrodes the outflow of gas from the probe can blow away or dry off any liquid remaining at the space between the electrodes thereby causing a liquid formed conducting path between the electrodes to vanish.


BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described, by way of example, with reference to the accompanying drawings in which:
FIG. 1 is a side view, partly in section, of a measuring probe formed according to the invention, in combination with a supply of gas shown diagrammatically and an electrical circuit;
FIG. 2 shows a modification which can be made to the probe in FIG. 1, and
FIG. 3 shows a possible arrangement, in use, of a plurality of probes, each as shown in FIG. 1, in combination with a supply of gas and an electronic indication circuit.


DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 1, a heat resistant measuring probe 2 comprises an electrode 4 comprising a tube 5 of circular cross-section about which extends a concentric, cylindrical electrode 6. These electrodes 4,6 may be of any suitable heat resistant, electrically conducting material, for example, stainless steel. The electrode 6 is disposed as an inverted cup formed by a substantially flat cap portion 8 from which depends an annular skirt 10. The two electrodes 4,6 are spaced one from the other by a heat resistant, electrically insulating spacer 12 which is preferably mechanically strong. The spacer 12 may be of ceramic material. A possible ceramic material for the insulating space 12 is "SCHUMALITH SC" Filter Candle, Grade 5 available from Schumacher Filters Ltd. of Parkway Industrial Estate, Sheffield, England. The spacer 12 is of substantially cylindrical shape having its circumferential surface 14 attached to the inner surface of the skirt 10 by, for example, heat resistant adhesive. Electrode 4 is disposed in a

REFERENCES:
patent: 1978392 (1934-10-01), Brockdorff
patent: 2498232 (1950-02-01), Andrews
patent: 4382382 (1983-05-01), Wang
patent: 4383544 (1983-05-01), Vosper
patent: 4465088 (1984-08-01), Vosper
Roughton, J. E., E. A. "Electromechanical Transducers in Hostile Environments", IEE Reviews, vol. 126, No. 11R, Nov. 1979, pp. 1029-1052.
Edwards, R. W., "Low Coolant Sensing Probe With Connector Corrosion Prevention", Research Disclosure, No. 288, Apr. 1988, Havant GB, p. 243.

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