Geometrical instruments – Indicator of direction of force traversing natural media – Level or plumb – terrestrial gravitation responsive
Patent
1990-03-14
1992-12-22
Haroian, Harry N.
Geometrical instruments
Indicator of direction of force traversing natural media
Level or plumb, terrestrial gravitation responsive
33377, G01C 906
Patent
active
051724812
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a device and, more particularly, but not exclusively to a sensor for an electronic level or inclination gauge.
Optical levels, more commonly called spirit levels, are well known and provide an optical indication of whether or not a surface is horizontal, based on the principle of an air bubble in a liquid-filled vial always seeking the highest point in the vial, the vial being slightly curved so that when at level, the bubble will always take up an equilibrium position. Such bubble levels, if disposed in a suitable frame, can also be used to provide an indication of whether or not a surface is vertical.
However, such spirit levels are not capable of measuring deviations from horizontal or vertical outside a very limited range. Also, such spirit levels can be difficult to read accurately as the measurement of level or plumb depends on the ability of the user to determine the position of the bubble. Factors such as poor lighting or poor eyesight obviously affect this.
An electronic spirit level has ben proposed by Cantarella, in U.S. Pat. No. 4,167,818, which uses a capsule part-filled with a conductive liquid. Several electrodes are disposed within the capsule, the resistance between the electrodes being dependent on the position of the liquid within the capsule which, in turn, is dependent upon its inclination. A digital readout of angles of inclination from level and from plumb is provided. However, this level, again, is only usable over a limited range of angular deviation from horizontal or vertical.
Capacitive devices, such as that disclosed in EP 35840 have also been proposed. The device of EP 35840 includes a capsule of generally cylindrical form part-filled with a liquid having a dielectric constant different from that of the remainder of the capsule. The capsule is provided with four electrodes, a single, primary, electrode being disposed on one end surface of the capsule and the three other, secondary, electrodes being disposed on the other end surface. Three sensing circuits including three oscillators are provided for sensing the capacitance between the first electrode and the three secondary electrodes.
However, the three secondary electrodes each need a separate processing circuit. As each processing circuit tends to have its own individual characteristics, compensation for this is also necessary. This factor leads to additional manufacturing expense.
According to the invention in a first aspect, there is provided a sensor for an inclination measuring device comprising: within the capsule, the relative degree of immersion of the first and second electrodes in the liquid being indicative, within a first angular range, of the angle of inclination of the capsule both about a reference axis and relative to a first reference angle. within the capsule, the relative degree of immersion of the third and fourth electrodes in the liquid being indicative, within a second angular range, of the angle of inclination of the capsule both about the reference axis and relative to a second reference angle different from the first reference angle; and inclination of the capsule about the reference axis is included within at least one of the first and second ranges and the first and second reference angles are those at which the electrodes of the first and second electrode means, respectively, are substantially equally immersed in the liquid.
According to the invention in a second aspect there is provided an inclination measuring device comprising a capsule part-filled with a liquid, the position of the liquid within the capsule being indicative of the angle of rotation of the capsule about a reference axis, a plurality of electrodes, disposed within the capsule for sensing said position, within an angular range, an excitation source, a sensing circuit and switching means for connecting said electrodes to the sensing circuit and to the excitation source in a plurality of configurations for measuring, sequentially, a plurality of electrical characteristics of the liquid which together are
REFERENCES:
patent: 4028815 (1977-06-01), Buckley et al.
patent: 4641434 (1987-02-01), Engler
Ryan Paul T.
Wiseman Colin P.
Wyatt-Millington Charles W.
Haroian Harry N.
The Stanley Works
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