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  With the laser set to level or grade, at a given distance, how far from perfection will the laser beam be. Usually expressed as plus or minus a fraction of an inch at 100 feet. (Or ±Xmm at 30m) Accuracy may also be expressed in terms of arc seconds.10 Arc Seconds translates to ±1/16" at 100'. (±1.6mm at 30M.) Accuracy decreases with distance from the laser. If the accuracy of a laser is ±1/16" per 100 feet, it will be ±1/8" at 200 feet.


Arc Second  


A circle can be divided into 360 degrees. Each degree is divided into 60 arc minutes, and each arc minute is divided into 60 arc seconds.


 Automatic Leveling  


Automatic Leveling and Self Leveling are used synonymously. The major types of self leveling systems are servo motor and compensated. In the servo motor system, electronic level sensors send information to a processor, which activates motors that drive the laser to level. A compensator is a gravity based pendulum mechanism. Servo laser systems have a much greater self leveling range than compensated laser systems. In a compensated system, the user turns leveling screws to center a level vial. Once the laser is rough leveled, the compensator maintains the laser reference at its specified accuracy. When using a servo system, the user mounts the laser on a tripod, turns on the power, and waits for the laser to drive itself to level.




Gravity type mechanism, usually some type of pendulum system to insure that laser beam is level. Compensators may be wire or bearing hung




A rotating laser can be made to project a non-flat reference that slopes either up or down from the center (imagine a funnel shaped pattern). Low quality products sometimes project a cone due to poor optics, or design. A construction laser such as the L6C projects a precision cone that can be adjusted to fit specific jobsite needs.




Usually applied to a laser receiver. This is the distance that a receiver can be moved and still give an on grade reading. If the deadband is too fine, it becomes difficult to get an on grade reading, if the deadband is too wide, it becomes difficult to maintain accuracy.


Grade Capability  


The range of slope that can be dialed into the laser. Expressed as percent of slope.


Laser Diode  


Solid state device that produces laser light. Laser light can be visible or invisible. Construction lasers use one of three wavelengths. They are infra-red (invisible, 780nm), red (650 or 635nm), and green (532nm). 




Acronym for Light Amplification by Stimulated Emission of Radiation


Manual Leveling  


The laser is kept level through the use of glass level vials. The user must check these vials periodically, because the level bubbles may move during the day, in response to vibrations and changes in temperature.


Operating Range  


The maximum distance from the laser where the detector will still function properly. Usually given in terms of an operating radius or diameter.


Penta Mirror or Penta Prism  


Device that reflects a laser beam outward at a 90º angle in relation to the incoming beam.


Rotational Coverage  


The circle of working coverage around the laser. Most lasers offer a full 360º circle of coverage.


Self Leveling  


Construction lasers are leveled either with a compensator, or with an electronic servo motor system. If the laser is disturbed or goes out of level, the mechanism will make a correction. If the mechanism cannot bring the laser fully back to level, it shuts the laser off.


Self Leveling Range  


Expressed as ± x number of degrees or arc minutes. This figure denotes how far the laser can be tilted, while still maintaining its ability to self level

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