Where a spirit Bubble level must be usable upside-down or on its side, the curved constant-diameter tube is replaced by an uncurved barrel-shaped tube with a slightly larger diameter in its middle.
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Where a spirit Bubble level must be usable upside-down or on its side, the curved constant-diameter tube is replaced by an uncurved barrel-shaped tube with a slightly larger diameter in its middle.
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Variant of the linear spirit Bubble level is the bull's eye Bubble level: a circular, flat-bottomed device with the liquid under a slightly convex glass face with a circle at the center.
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The level is placed on a flat and roughly level surface and the reading on the bubble tube is noted.
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The spirit Bubble level is then rotated through 180 degrees in the horizontal plane, and another reading is noted.
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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 the magnitude of the reading remains constant when the level is flipped.
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Similar procedure is applied to more sophisticated instruments such as a surveyor's optical Bubble level or a theodolite and is a matter of course each time the instrument is set up.
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The sensitivity of a level is given as the change of angle or gradient required to move the bubble by unit distance.
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Spirit Bubble level is usually found on the head of combination squares.
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Traditional carpenter's spirit Bubble level looks like a short plank of wood and often has a wide body to ensure stability, and that the surface is being measured correctly.
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Line Bubble level is a Bubble level designed to hang on a builder's string line.
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The body is lightweight, so as not to weigh down the string line, it is small in size as the string line in effect becomes the body; when the Bubble level is hung in the center of the string, each 'leg' of the string line extends the Bubble level's plane.
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The Bubble level was so accurate it was restricted from export during World War II.
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Production of the Bubble level stopped around 1970, and was restarted in the 1980s by Thomas Butler Technology, of Rockford, Illinois, but finally ended in the mid-1990s.
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Today Bubble level tools are available in most smartphones by using the device's accelerometer.
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