Measuring and testing – Volume or rate of flow – By measuring electrical or magnetic properties
Patent
1995-02-22
1996-10-01
Chilcot, Richard
Measuring and testing
Volume or rate of flow
By measuring electrical or magnetic properties
7386108, 7386173, G01F 158, G01F 156, G01F 160
Patent
active
055602460
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a device for measuring a mass flow which is deflected at the outlet of an elevator at a conveyor shaft wall, in particular of a harvester, so that it forms a stratified dielectric with a homogeneous speed in a flow rate measuring capacitor disposed there. The first capacitor plate of the flow rate measuring capacitor is disposed at the mass flow side, the second capacitor plate is disposed at a distance from the mass flow. In the process the first capacitor plate is bordered by a protective electrode which is kept at the same potential with the enclosed capacitor plate by means of an impedance transformer. The second capacitor plate is formed by a conveyor shaft wall located opposite the first capacitor plate and by lateral areas of the conveyor shaft.
The mass flow is guided through the flow rate measuring capacitor in such a way that it forms a stratified dielectric with an approximately homogeneous velocity distribution and is passed through a second measuring capacitor which is always completely filled. The two capacitances of these capacitors are detected by means of the same measuring device in order to form a capacitance proportion.
The continuous absolute value measurement of a grain flow in harvesters results in considerable advantages when employing the measured value for controlling and monitoring the operation of the machine, in particular the feed speed, the sifter drives and the cutting height. Further than that, it also permits the preparation of a harvest register which is a basis for soil treatment and fertilization extending over years and adapted to the respective soil and harvest values.
A device of this type is the subject of German Patent Application P 41 05 857 A1.
The measuring device is disposed in the harvester behind the grain elevator, for example a power shovel, in a path bend wherein the mixing of the grain, which is ejected from different path radii and which in the process has different velocities, takes place, wherein the centrifugal force occurring at the bent wall causes packing of the grain and velocity homogenization. The smooth guide path and the evened-out flow of the grain precludes damage of the delicate harvested material.
Different circuit arrangements are suitable for the capacitance comparison measurement, wherein advantageously always the same measuring device is used for measuring both capacitances, so that systematic errors cancel each other out to a large degree.
A first suitable measuring arrangement is distinguished by a carrier frequency measuring bridge, whose input is alternately switched to the two capacitances to be measured and whose associated measured results are compared in a computer.
A further circuit arrangement consists in that the two capacitances to be measured are switched into a carrier bridge as bridge members, so that the bridge output signal is a value for determining the capacitance proportion.
Another type of capacitance proportion measuring takes place in a circuit, in which a capacitance charge of the capacitors by means of a current source is alternatingly performed up to a comparison voltage, wherein the respectively required charge times of the two measuring capacitors are measured, which then must be compared.
A further circuit arrangement, wherein the two capacitances to be compared are disposed in the branches of a bridge circuit, results in a particularly rapid and accurate measurement. In the process an immediate proportion formation takes place, which must then be reduced in accordance with the known functional connection of the bridge circuit to the capacitance proportion, which takes place in a simple calculation by means of equations or association in a table. This functional transformation can be combined with the functional linkage, required anyway, of the capacitance proportion with the function of the stratified dielectric, so that respectively only a mutual processing of a measured result by means of an access to a table or a function calculation is required.
In an embodiment of the bridge m
REFERENCES:
patent: 4930356 (1990-06-01), Proges
patent: 5343761 (1994-09-01), Myers
patent: 5351558 (1994-10-01), Horn et al.
patent: 5431883 (1995-07-01), Barraud
Bottinger Stefan
Horn Klaus
Weigelt Horst
Yang Weiping
Chilcot Richard
Claas oHG Beschrankt haftende offene Handelsgesellschaft
Noori Max
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