Geometrical instruments – Indicator of direction of force traversing natural media – Level or plumb – terrestrial gravitation responsive
Patent
1990-11-01
1992-12-15
Haroian, Harry N.
Geometrical instruments
Indicator of direction of force traversing natural media
Level or plumb, terrestrial gravitation responsive
33377, G01C 900
Patent
active
051705672
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.
Electronic spirit levels have been proposed, for example 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 such levels suffer the disadvantage that the accuracy of any measurement from horizontal or vertical is dependent upon ambient conditions such as temperature, as fluctuations in temperature will lead to variations in the level and resistance of liquid within the capsule which in turn will affect the reading of inclination for angles for which the electrodes are not equally immersed in the liquid.
According to the invention in a first aspect there is provided a capsule, part filled with a liquid, the volume of the liquid varying as a function of temperature and the capsule being elastically deformable in response to temperature-induced pressure change within the capsule, so that the internal volume of the capsule is variable in dependence upon temperature and whereby dimensions and material of walls of the capsule are selected to provide a predetermined relationship between the level of liquid within the capsule and temperature.
According to the invention, in a second aspect there is provided a capsule, part-filled with a liquid, the walls or the capsule being formed so that a temperature-induced pressure change within the capsule will cause the walls of the capsule to deform elastically to maintain the level of the liquid in the capsule substantially constant.
In the described embodiment of the invention a cylindrical capsule is provided, the bulging of the radial walls of the capsule in response to increased pressure within the capsule being chosen, by selecting the thickness and material for the radial walls, so that temperature induced increase in volume of the liquid is compensated by increased volume of the capsule, brought about by the change in configuration of the capsule radial walls, to maintain the liquid level substantially constant.
Alternatively, the change in configuration of the capsule radial walls is selected so that the liquid level fluctuates with temperature in a predetermined way.
In a particular application described, the capsule is used in an inclination measuring device in which measured resistances between electrodes disposed in the capsule and the liquid are dependent on inclination and prone to fluctuation with temperature, due to changes in liquid level within the capsule and also due to fluctuations in the resistance of switches connected to the electrodes in relation to the resistance of the liquid. The fluctuations due to liquid level may be compensated for by adjusting the volume of the capsule in the manner mentioned above. However, by allowing the volume of the capsule to change in a predetermined way which allows the level to fluctuate i
REFERENCES:
patent: 2584917 (1952-02-01), Powell
patent: 3906471 (1975-09-01), Shawhan
patent: 4028815 (1977-06-01), Buckley et al.
Bates Stephen J.
Davis Kelvin R.
Murray Andrew J.
Haroian Harry N.
The Stanley Works
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