GB2035574A - Moisture content measuring apparatus - Google Patents

Abstract

Apparatus is disclosed for measuring the moisture content of grain samples or the like, comprising a casing 10 affording a supporting surface for a sample, and means 12 for compressing the sample against the supporting surface. The supporting surface incorporates two electrodes 16, 18, one of which 18 has an electrical temperature sensing element embedded in it. The apparatus includes electrical circuitry by means of which the resistance between said electrodes and the temperature sensed by said temperature sensing element is measured and an output signal corresponding to the moisture content, calculated on the basis of said electrical resistance with a correction for temperature, is provided. The means for compressing the sample may be a manually 34 operable compression screw 26 incorporating a transmission adapted to slip at a predetermined torque. <IMAGE>

Description

SPECIFICATION Moisture content measuring apparatus THIS INVENTION relates to apparatus for measuring the moisture content of a granular or pulverulent material, for example a vegetable product, such as grain, e.g. with a view to determining whether it may be safely stored without risk of deterioration.

According to one aspect of the invention, there is provided apparatus for measuring the moisture content of a material, including means for engaging a body of a material the moisture content of which is to be measured, said means including electrodes for engagement with a said body of material, and a temperature sensing means, the apparatus including electrical measurement means for measuring elec trically the resistance between said electrodes, means for deriving an electrical signal correspondings to the temperature sensed by said temperature sensing means, and electrical processing means operable to provide an output signal indicative of the moisture content of said material, which signal is a function of said resistance and temperature measured.

The output signal may be in the form of an analogue signal, a coded digital signal in serial form or in parallel form provided on a plurality of conductors, or may be in visual form and be provided by an electrically operable display means, for example a galvanometer or a digital display, or may take any other conventional form.

According to another aspect of the invention there is provided a moisture content measuring apparatus including electrodes adapted to be placed in contact with a material the moisture content of which is to be measured, means for measuring electrically the resistance between said electrodes, and an electrical temperature sensing means embedded in at least one of said electrodes and operable to provide an electrical signal indicative of the temperature of said one electrode and thus of the material in contact with the same, whereby an indication of the moisture content of said material may be gained from measurement of said resistance and the temperature as sensed by said temperature sensing means.

According to yet another aspect of the invention, there is provided a moisture content measuring apparatus including an outer casing, electrodes insulated from one another by insulating material, said electrodes and said insulating material providing respective surfaces exposed on the exterior of the casing and forming respective parts of a continuous smooth outer surface of said casing, means within said casing for sensing the electrical resistance between said electrodes as a measure of the resistivity, and hence the moisture content, of a material engaging the part of the outer surface of the casing provided by said electrodes and insulating material, and means for pressing a material, the moisture content of which is to be measured, against said part of the outer surface of the casing.

According to yet another aspect of the invention, there is provided a moisture content measuring apparatus including electrodes insulated with respect to each other and exposed on a first surface, means for sensing the electrical resistance between said electrodes as a measure of the resistivity, and hence the moisture content, of a material engaging and bridging said electrodes, a compression member being provided having a surface opposing or opposable to the exposed surfaces of said electrodes and manually operable means being provided for moving said compression member towards said electrodes, via a force transmission system incorporating slipping means arranged to slip under a predetermined stress to limit to a predetermined value compression to which a body of material disposed between said compression member and said electrodes can be subjected by operation of said manually operable means.

Preferably said transmission system comprises a screw carrying said compression member, and a handle by means of which said screw can be turned, and said slipping means comprises a clutch disposed between said handle and said screw and arranged to slip at a predetermined torque exerted therethrough on the screw by the handle.

An embodiment of the invention is described below with reference to the accompanying drawing wherein: Figure 1 is a highly diagrammatic exploded perspective view of a moisture-control measuring apparatus embodying the invention, and Figure 2 is a similarly diagrammatic side view, partly in section, of part of the apparatus of Figure 1.

Referring to Figure 1, the apparatus for measuring the moisture content of a vegetable product, such as grain, comprises a first portion, housed in an outer casing 10, a second portion, namely a compression means 12, and a third portion, in the form of a ring 14 for containing material to be tested within a predetermined area.

The apparatus comprises an outer electrode 16 providing an exposed surface, annular in shape, lying in the plane of the flat top surface of the casing 10, and a central electrode 18, providing a circular exposed surface also lying in the plane of the flat top surface of the casing 10, within the area bounded by the annular exposed surface of the outer electrode and disposed concentrically with respect to said annular surface. The electrodes are insulated from each other by insulating material 20 also providing, between the electrodes 16 and 18 an exposed surface lying in the plane of the top of the casing 10.

Thus the electrodes 16, 18 and the insulating material 20 are flush with the upper surface of the casing, a feature which allows easy and effective cleaning of the electrode and insulator assembly, thereby eliminating errors arising from contamination of the electrode and insulator surfaces.

In use of the apparatus to determine the moisture content of a sample of grain, the containing ring 14 is placed on the top of casing 10 so as to encircle the region of the electrodes 16, 18, the sample is then placed within the ring 14 so as to cover the electrodes 16, 18, and the compression means 12 is fitted over the sample.

In the drawings, the compression means 12 is represented as comprising a compression member 24 in the form of a cylindrical piston of a size to fit freely within ring 14, the piston 24 being carried at the lower end of a screw 26 which is in screw-threaded engagement with an internal screw thread in a hous ing 28 whereby the screw can be advanced or retracted longitudinally with respect to the housing 28 by rotating the screw in the housing.The housing 28 is preferably detachably secured to the part 10, for example by means of a flange 30, integral with the housing and having keyhole slots 32 which, when the means 12 is fitted to the part 10 receive headed pins 34 projecting from the top surface of the part 10, the means 12 being detachable from the housing simply by twisting about its vertical axis to place the wider parts of slots 32 directly under the heads of the pins 34 and lifting the means 12. Thus the housing 28 is detachably secured to the part 10 buy a quickrelease bayonet connection. A similar flange, also provided with corresponding keyhole slots, may be provided on the ring 14, as shown, to locate on the pins 34 under the flange 30, so that the ring 14 is located in the desired position.

The means 12 also includes a handle 34 which is coupled with the screw 26 via a slipping clutch (not shown) arranged to allow the handle 34 to slip rotationally with respect to the screw 26 so as to prevent torques in excess of a predetermined value from being applied to the screw via the handle 34. Thus when the means 12 is fitted overthe sample, as described above, with the flange 30 engaging under the heads of the pins 34, the piston 24 fits within the ring 14 above the sample.

The handle 34 is then turned to turn the screw 26 and advance the same so that the sample is compressed between the piston 24 and the electrodes 16, 18 and insulator 20. The handle 34 is turned until the slipping clutch begins to slip, signifying that the sample has been compressed to a predetermined standard extent.

The electrical resistance between electrode 16 and electrode 18, i.e. the resistance to current flow between these electrodes through the sample 22, is measured by electronic circuitry within the casing 10, the electrodes being connected with said circuitry by, for example, conductors 40,42 shown in Figure 2.

It is known that the electrical resistance of a sample of grain under a predetermined compression varies not only as a function of its moisture content, but also as a function of its temperature. In order to allow account to be taken automatically ofthe temperature of the sample, a thermistor 44 is embedded in one of the electrodes, for example the central electrode 18, the leads from the thermistor being connected to said electronic circuitry, and the circuitry operates to provide an electrical output signal, applied to a galvanometer 46 mounted in the casing 10 which corresponds to the moisture content as determined in accordance with the electrical conductivity compensatedfortemperature.

It will be appreciated that many variations of an modifications to the apparatus described with refer ence to the drawings are possible within the scope of the invention. Thus, for example the nature of the compression means 12 may be different from that shown and the manner of its mounting on the part 10 may be varied.

Similarly, the electronic circuitry disposed within the casing 10 may be partly digital in nature, and the galvanometer 46 may, for example, be replaced by a digital display driven by the electronic circuitry.

Claims (7)

1. Apparatus for measuring the moisture content of a material, including means for engaging a body of a material the moisture content of which is to be measured, said means including electrodes for engagement with a said body of material, and a temperature sensing means, the apparatus including electrical measurement means for measuring electricallythe resistance between said electrodes, means for deriving an electrical signal corresponding to the temperature sensed by said temperature sensing means, and electrical processing means operable to provide an output signal indicative of the moisture content of said material, which signal is a function of said resistance and temperature measured.

2. Apparatus for measuring the moisture content of a material including electrodes for placing in contact with a material the moisture content of which is to be measured, means for measuring electrically the resistance between said electrodes, and an electrical temperature sensing means embedded in at least one of said electrodes and operable to provide an electrical signal indicative of the temperature of said one electrode and thus of the material in contact with the same, whereby an indication of the moisture content of said material may be gained from measurement of said resistance and the temperature as sensed by said temperature sensing means.

3. Apparatus for measuring the moisture content of a material, the apparatus including an outercas- ing, electrodes insulated from one another by insulating material, said electrodes and said insulating material providing respective surfaces exposed on the exterior of the casing and forming respective parts of a continuous smooth outer surface of said casing, means within said casing for sensing the electrical resistance between said::electrodes as a measure of the resistivity, and hence the moisture content of a material engaging the part of the outer surface of the casing provided by said electrodes andsinsulating material, and means for pressing a materiaI,the moisture content of which is to be measured, against said part of tile outer surface of the casing.

4 Apparatus for measuring the moisture content ia material, the apparatus including electrodes insulated with respect to each. other and exposed on a first surface, means for sensing the electrical resistance between saidelectrodesasa measure of the resistivity, and hence the moisture content, of a mat erial engaging and bridging said electrodes, a compression memberbeing provided having a surface opposing or opposable to the exposed surfaces of said electrodes, a force transmission system incorporating slipping means arranged to slip under a predetermined stress and manually operable means being provided for moving said compression member towards said electrodes, via said force transmission system, said force transmission system serving to limitto a predetermined value the compression to which a body of material disposed between said compression member and said electrodes can be subjected by operation of said manually operable means.

5. Apparatus according to claim 4 wherein said transmission system comprises a screw carrying said compression member, and a handle by means of which said screw can be turned, and said slipping means comprises a clutch disposed between said handle and said screw and arranged to slip at a predetermined torque exerted therethrough on the screw by the handle.

6. Apparatus substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

7. Any novel feature or combination of features described herein.