A spirit level or bubble level is an instrument designed to indicate whether a surface is horizontal (level) or vertical (plumb). Different types of spirit levels may be used by carpenters, stonemasons, bricklayers, other building trades workers, surveyors, millwrights and other metalworkers, and in some photographic or videographic work.
Original spirit levels had two banana-shaped curved glass vials at each viewing point and were much more complicated to use. In the 1920s, Henry Ziemann invented the modern level with a single vial. These vials, common on most ordinary levels today, feature a slightly curved glass tube which is incompletely filled with a liquid, usually a colored spirit or alcohol, leaving a bubble in the tube. At slight inclinations the bubble will travel away from the center position, which is usually marked in some manner.
Alcohols such as ethanol are often used rather than water for a variety of reasons. Alcohols generally have very low viscosity and surface tension, which allows the bubble to travel the tube quickly and settle accurately with minimal interference with the glass surface. Alcohols also have a much wider liquid temperature range, and won't break the vial as water could due to ice expansion. A colorant such as fluorescein, typically yellow or green, may be added to increase the visibility of the bubble.
Some spirit levels are capable of indicating the level of a surface between horizontal and vertical to the nearest degree. An extension of the spirit level is the bull's eye level: a circular, flat-bottomed device with the liquid under a slightly convex glass face which indicates the center clearly. It serves to level a surface across a plane, while the tubular level only does so in the direction of the tube. The most sophisticated spirit levels are guaranteed accurate to five-ten-thousandths (.0005) of an horizontal inch at the center per vertical inch at either end. Where a spirit level must also be usable upside-down, the banana-shaped tube is replaced by a barrel-shaped tube. The upper internal surface of the tube is thus always of an appropriate shape.
Adjustment of the spirit level is performed by successively rotating the level and moving the bubble tube within its housing to take up roughly half of the discrepancy. Until when the level is flipped the buble does not move its relative position. Note that a perfectly horizontal surface isn't required.
A similar procedure is applied to more sophisticated instruments such as a surveyor's level or a theodolite and is a matter of course each time the instrument is set up. In this latter case, the plane of rotation of the instrument is levelled, along with the spirit level. Furthermore this is done in two horizontal perpendicular directions.
A spirit level is also usually found on the head of combination squares.
See: Spirit leveling
An engineer's precision level permits leveling items to a greater degree of accuracy than a plain spirit level. They are used to level the foundations, or beds of machines to ensure the machine can output workpieces to the accuracy pre-built in the machine.
Thevenot is often confused with his nephew, the traveler Jean de Thevenot (born 1633; died 1667). There is evidence to suggest that both Huygens and Hooke later laid claim to the invention, although only within their own countries.
Category:Surveying Category:Geodesy Category:Inclinometers Category:Woodworking measuring instruments
ar:ميزان التسوية (ميزان الماء) ca:Nivell (instrument) cs:Vodováha da:Vaterpas de:Wasserwaage es:Nivel (instrumento) eo:Nivelilo fr:Niveau à bulle ga:Leachtleibhéal hr:Libela io:Libelo it:Livella he:פלס בנאים pam:Nibel hu:Vízmérték nl:Waterpas ja:水準器 no:Vaterpass pl:Poziomica pt:Nível ro:Nivelă ru:Уровень (инструмент) scn:Livedda sk:Vodováha (bublinková) szl:Waserwoga sr:Либела sh:Libela fi:Vesivaaka sv:Vattenpass uk:Ватерпас vi:Ống bọt nước zh-yue:平水尺 zh:水準管This text is licensed under the Creative Commons CC-BY-SA License. This text was originally published on Wikipedia and was developed by the Wikipedia community.
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