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37-487: Laying is the act of making equipment level. It usually involves moving equipment in small motions so that spirit levels are centralised in all planes . Movement is usually done by small worm gears or other fine setting devices for accurate small movements, together with coarser gears to allow large swings in motion for quick movement between different settings. Equipment that requires laying before it can be used accurately includes: This industry -related article

74-464: A "construction level", "heavy duty level", "inclinometer", or "protractor". These modern electronic levels are capable of displaying precise numeric angles within 360° with 0.1° to 0.05° accuracy, can be read from a distance with clarity, and are affordably priced due to mass adoption. They provide features that traditional levels are unable to match. Typically, these features enable steel beam frames under construction to be precisely aligned and levelled to

111-452: A builder's string line. The body of the level incorporates small hooks to allow it to attach and hang from the string line. The body is lightweight, so as not to weigh down the string line, it is also small in size as the string line in effect becomes the body; when the level is hung in the center of the string, each 'leg' of the string line extends the level's plane. An engineer's precision level permits leveling items to greater accuracy than

148-400: A circular, flat-bottomed device with the liquid under a slightly convex glass face with a circle at the center. It serves to level a surface across a plane, while the tubular level only does so in the direction of the tube. To check the accuracy of a carpenter's type level, a perfectly horizontal surface is not needed. The level is placed on a flat and roughly level surface and the reading on

185-470: A machine bed and show tilt on the x-y axes simultaneously, eliminating the need to rotate the level 90 degrees. The level was so accurate it was restricted from export during World War II . The device set a new standard of .0005 inches per foot resolution (five ten thousands per foot or five arc seconds tilt). Production of the level stopped around 1970, and was restarted in the 1980s by Thomas Butler Technology, also of Rockford, Illinois, but finally ended in

222-413: 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. Combining a spirit level with an optical telescope results in a tilting level or dumpy level . These leveling instruments as used in surveying to measure height differences over larger distances. A surveyor's leveling instrument has

259-427: A previous survey or an arbitrary point with an assumed height is used. Sighting is done with an assistant surveyor who holds a graduated staff vertical at the point under measurement. The surveyor rotates the telescope until the graduated staff is in the crosshairs and records the reading. This is repeated for all sightings from that datum. Should the instrument be moved to another position within sighting distance, it

296-404: A short plank of wood and often has a wide body to ensure stability, and that the surface is being measured correctly. In the middle of the spirit level is a small window where the bubble and the tube is mounted. Two notches (or rings) designate where the bubble should be if the surface is level. Often an indicator for a 45 degree inclination is included. A line level is a level designed to hang on

333-548: A spirit level mounted on a telescope (perhaps 30 power) with cross-hairs, itself mounted on a tripod . The observer reads height values off two graduated vertical rods, one 'behind' and one 'in front', to obtain the height difference between the ground points on which the rods are resting. Starting from a point with a known elevation and going cross country (successive points being perhaps 100 meters (328 ft) apart) height differences can be measured cumulatively over long distances and elevations can be calculated. Precise levelling

370-583: A year of this date the inventor circulated details of his invention to others, including Robert Hooke in London and Vincenzo Viviani in Florence . It is occasionally argued that these "bubble levels" did not come into widespread use until the beginning of the 18th century, the earliest surviving examples being from that time, but Adrien Auzout had recommended that the Académie Royale des Sciences take "levels of

407-460: Is a stub . You can help Misplaced Pages by expanding it . Spirit level The history of the spirit level was discussed in brief in an 1887 article appearing in Scientific American . Melchisédech Thévenot , a French scientist, invented the instrument some time before February 2, 1661. This date can be established from Thevenot's correspondence with scientist Christiaan Huygens . Within

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444-424: 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. This is done in two horizontal perpendicular directions. Sensitivity is an important specification for a spirit level, as the device's accuracy depends on its sensitivity. The sensitivity of a level is given as the change of angle or gradient required to move

481-462: Is re-levelled, and a sighting taken of a known level in the previous survey. This relates any new levels to the previous levels. The Y level or wye level is the oldest and bulkiest of the older style optical instruments. A low-powered telescope is placed in a pair of clamp mounts, and the instrument then leveled using a spirit level , which is mounted parallel to the main telescope. The term dumpy level (also builder's level ) endures despite

518-420: Is rotated and focused until the level staff is plainly visible in the crosshairs. In the case of a tilting level, the fine level adjustment is made by an altitude screw, using a high accuracy bubble level fixed to the telescope. This can be viewed by a mirror whilst adjusting, or the ends of the bubble in a "split bubble" display can be viewed within the telescope. This also allows assurance of the accurate level of

555-403: Is shown on a digital display. This type of level removes interpolation of graduation by a person, thus removing a source of error and increasing accuracy. During night time, the dumpy level is used in conjunction with an auto cross laser for accurate scale readings. A transit level also has the ability to measure both the altitude and azimuth of a target object with respect to a reference in

592-710: Is supposed to give the difference in elevation between two points one kilometer (0.62 miles) apart correct to within a few millimeters. Alternatives include: Today level tools are available in most smartphones by using the device's accelerometer . These mobile apps come with various features and easy designs. Also new web standards allow websites to get orientation of devices. Digital spirit levels are increasingly common in replacing conventional spirit levels, particularly in civil engineering applications such as traditional building construction and steel structure erection, for on-site angle alignment and leveling tasks. The industry practitioners often refer to those levelling tools as

629-506: The Thevenot type" on its expedition to Madagascar in 1666. It is very likely that these levels were in use in France and elsewhere long before the turn of the century. The Fell All-Way precision level, one of the first successful American made bull's eye levels for machine tool use, was invented by William B. Fell of Rockford, Illinois in 1939. The device was unique in that it could be placed on

666-434: The bubble by unit distance. If the bubble housing has graduated divisions, then the sensitivity is the angle or gradient change that moves the bubble by one of these divisions. 2 mm (0.079 in) is the usual spacing for graduations; on a surveyor's level, the bubble will move 2 mm (0.079 in) when the vial is tilted about 0.005 degree. For a precision machinist level with 2 mm (0.079 in) divisions, when

703-416: The bubble to travel the tube quickly and settle accurately with minimal interference from the glass surface. Alcohols also have a much wider liquid temperature range, and will not 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. A variant of the linear spirit level is the bull's eye level :

740-416: The bubble tube is noted. This reading indicates to what extent the surface is parallel to the horizontal plane, according to the level, which at this stage is of unknown accuracy. The spirit level is then rotated through 180 degrees in the horizontal plane, and another reading is noted. If the level is accurate, it will indicate the same orientation with respect to the horizontal plane. A difference implies that

777-435: The center, the highest point. At slight inclinations the bubble travels away from the marked center position. Where a spirit level must also 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. Alcohols such as ethanol are often used rather than water. Alcohols have low viscosity and surface tension , which allows

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814-453: The coarse levelling of the instrument, and are thereby quicker to use. The optical level should not be confused with a theodolite , which can also measure angles in the vertical plane. The complete unit is normally mounted on a tripod , and the telescope can freely rotate 360° in a horizontal plane. The surveyor adjusts the instrument's level by coarse adjustment of the tripod legs and fine adjustment using three precision levelling screws on

851-413: The dumpy level is permanently secured to its two support arms and the levelling mechanism, thereby reducing measurement uncertainty and considerably reducing the time taken to set up the instrument. The dumpy uses the same basic principle of level sighting. After careful setup of the level, the height of the crosshairs is determined by either sighting from a known benchmark with known height determined by

888-438: The evolution in design. They can be manual or automatic, the latter being much quicker to set up. A tilting level is a variant which has a precision vertical adjustment screw which tilts both the telescope and the high accuracy bubble level attached to it to make them level. This reduces the complete reliance on the levelling accuracy of the instruments' bottom mount, and the "split bubble" display gives additional assurance that

925-413: The historic "Y" level is held in two brass arms, which are part of the mount and the telescope could be easily removed to allow sighting reversal though 180 degrees or an axial rotation of the telescope; both to compensate for optical collimation errors. Because the telescope is not fixed to the level adjusting mechanism, the "Y" instrument is assembled and disassembled for each sighting station. However,

962-408: The historic "Y" level. It operates on the principle of establishing a visual level relationship between two or more points, for which an inbuilt optical telescope and a highly accurate bubble level are used to achieve the necessary accuracy. Traditionally the instrument was completely adjusted manually to ensure a level line of sight, but modern automatic versions self-compensate for slight errors in

999-419: The horizontal plane. The instrument is rotated to sight the target, and the vertical and horizontal angles are read off calibrated scales In the first chapter of Thomas Hardy's 1887 novel The Woodlanders , the narrator states, "He knew every subtle incline of the ten miles of ground between Abbot's Cernel and Sherton—the market town to which he journeyed—as accurately as any surveyor could have learnt it by

1036-414: The instrument to make the rotational plane horizontal. The surveyor does this with the use of a bull's eye level built into the instrument mount. The surveyor looks through the eyepiece of the telescope while an assistant holds a vertical level staff which is graduated in inches or centimeters. The level staff is placed with its foot on the point for which the level measurement is required. The telescope

1073-400: The level is inaccurate. 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. A similar procedure is applied to more sophisticated instruments such as a surveyor's optical level or a theodolite and

1110-530: The level staff rested on the object or position being surveyed. In 1832, English civil engineer and inventor William Gravatt , who was commissioned to examine a scheme for the South Eastern Railway's route from London to Dover , became frustrated with the slow and cumbersome operation of the "Y" level during the survey work, and devised the more transportable, easier-to-use "dumpy" level, so called because of its shorter appearance. The telescope of

1147-400: The mid-1990s. However, there are still hundreds of the devices in existence. Early tubular spirit levels had very slightly curved glass vials with constant inner diameter at each viewing point. These vials are filled, incompletely, with a liquid – usually a colored spirit or alcohol – leaving a bubble in the tube. They have a slight upward curve, so that the bubble naturally rests in

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1184-408: The need to set the instrument base truly level, as with a dumpy level. Self-levelling instruments are the preferred instrument on building sites, construction, and during surveying due to ease of use and rapid setup time. A digital electronic level is also set level on a tripod and reads a bar-coded staff using electronic laser methods. The height of the staff where the level beam crosses the staff

1221-456: The required orientation, which is vital to ensure the stability, strength and rigidity of steel structures on sites. Digital levels, embedded with angular MEMS technology effectively improve productivity and quality of many modern civil structures. Some recent models feature waterproof IP65 and impact resistance features for harsh working environments. Optical level A level is an optical instrument used to establish or verify points in

1258-434: The same horizontal plane in a process known as levelling . It is used in conjunction with a levelling staff to establish the relative height or levels (the vertical separation ) of objects or marks. It is widely used in surveying and construction to measure height differences and to transfer, measure, and set heights of known objects or marks. It is also known as a surveyor's level, builder's level, dumpy level or

1295-630: The telescope is level whilst taking the sight. This allows faster operation as the bottom mount need not be truly level, though it will introduce a slight error as the vertical axis of the mount is not completely coincident with the telescope centre. The split bubble works by displaying half of both ends of the bubble side by side in the telescope, and when the curved ends are aligned it is level. An automatic level , self-levelling level , or builder's auto level includes an internal compensator mechanism (a swinging prism ) that, when set close to level, automatically removes any remaining variation. This reduces

1332-399: The telescope whilst the sight is being taken. However, in the case of an automatic level, altitude adjustment is done automatically by a suspended prism due to gravity, as long as the coarse levelling of the instrument base is accurate within certain limits. When level, the staff graduation readings at the crosshairs and stadia marks are recorded, and an identifying mark or marker placed where

1369-461: The vial is tilted one division, the level will change 0.04 mm (0.0016 in) one meter from the pivot point, referred to by machinists as 5 tenths per foot. This terminology is unique to machinists and indicates a length of 5 tenths of 1 thousandth of an inch. There are different types of spirit levels for different uses: A spirit level is usually found on the head of combination squares . A traditional carpenter's spirit level looks like

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