Line laser glossary
The terms you read on a line laser’s product page, defined in a sentence or two. Each definition stands on its own, with no need to read the rest.
- Self-levelling
- Automatic levelling of the instrument by a suspended pendulum, with no manual adjustment. It only works within a stated tilt range, commonly of the order of ±3° to ±4°; beyond that, the instrument must warn you, usually by flashing. How to choose a line laser
- Accuracy at 10 m
- The largest stated departure between the projected line and true horizontal, measured ten metres from the instrument. The error grows with distance: 3 mm at 10 m works out at 1.2 mm at four metres. Checking the accuracy
- Self-levelling range
- The largest tilt the pendulum takes up on its own, given in degrees and preceded by a ±. Outside that range the instrument is no longer reliable and must say so.
- Pulse mode
- A mode in which the beam is modulated at a set frequency so that a detector can pick it out from ambient light. It weakens the line seen by eye: in pulse mode, you read the detector. The laser detector
- Detector
- A unit that picks up a pulsed beam electronically and shows whether it sits above, below or on the line. It is what makes outdoor work possible, where the line becomes invisible. See the accessories
- Laser class
- The eye hazard category set out in standard EN/IEC 60825-1. Instruments sold to the general public in the United Kingdom fall under classes 1, 1M, 2 and 2M; in class 2 the power stays at or below 1 mW. The laser classes
- 360° plane
- A complete circle of light thrown around the instrument, without a break. Three planes — one horizontal, two vertical — make up what is called a 3D layout; four planes add a second horizontal. Cross, 3D, 4D or rotary
- Cross line laser
- An instrument that throws a horizontal and a vertical line crossing on the wall, each over a limited fan angle — often 110°. It does not go round the room: for that you need a model with 360° planes. See the cross line lasers
- Rotary laser
- An instrument that spins a single dot very fast to draw a plane. Concentrating the energy into one point gives it far more range than a line laser, at the cost of a detector you cannot do without.
- Range with a detector
- The distance at which the beam stays detectable by a detector, usually two to three times the range visible by eye. It never compares with a range stated without a detector. Stated range, real range
- Tilt mode
- A manual mode that switches off automatic levelling so you can set a deliberate slope. The pendulum is then locked: the instrument corrects nothing.
- IP rating
- Two digits describing resistance to dust and water. IP54 means protected against dust and against splashing water — not against immersion, and not against a jet.
- 1/4" and 5/8" threads
- The two standard mounting threads: 6.35 mm, inherited from photography, and 15.875 mm, the site standard. An adapter takes you from the second to the first.
- Levelling staff
- A graduated rule held upright, on which you read the height at which the laser plane crosses it. It turns a projected line into a figure, and carries the detector.
- Reflective target
- A small plate with a reflective coating, set on the point you are aiming at, which sends the beam back where the surface swallows it: bare concrete, dark timber, long distance.
- Viewing glasses
- Filtering lenses that raise the contrast of a laser line in a bright interior. They are not safety glasses: they help you see, they do not protect the eye.
- Reversal test
- A checking method: mark the line, turn the instrument through 180° without moving it, mark again. Half the gap between the two marks is the real error at that distance. The five-minute method
Frequent questions
What is a laser level?
An instrument that throws a line or a reference plane, horizontal or vertical, produced by a self-levelling pendulum. It replaces the step-by-step transfer of a spirit level: the reference lies in one piece across the room, and its deviation reads in millimetres at a stated distance.
What is a laser distance meter?
An instrument that measures a length by aiming at a target: it sends a pulse of light and derives the distance from the return time or the phase shift. It also works out areas, volumes and unreachable heights by Pythagoras. Its uncertainty applies to one reading, not to a projected plane.
What does an accuracy of ±3 mm at 10 m mean?
That the largest deviation stated by the manufacturer is three millimetres, measured ten metres from the instrument. Accuracy scales with distance: the same instrument drifts about 1.5 mm at five metres and 6 mm at twenty. Comparing two accuracies therefore requires the same distance.