Laser level outdoors: the detector becomes compulsory
Why does the line disappear outdoors?
A laser level meant for the general public is limited, by standard EN/IEC 60825-1, to a very low power — at or below 1 mW in class 2. That power is more than enough in a room, where the ambient light is modest.
In full sun, the light falling on the surface you are aiming at is thousands of times greater. The line is still there physically, but its contrast against the background becomes too weak for the eye to pick out. Raising the power is not an option: that would mean leaving the classes allowed for sale to the public.
From what distance?
There is no fixed threshold, because everything depends on the light and the surface. Indoors under artificial light the line stays readable over about ten metres; in full sun it can vanish at three. The order of magnitude, on the other hand, is steady:
| Conditions | Line visible by eye |
|---|---|
| Indoors, dimly lit room | The whole stated range |
| Indoors, very bright, large glazing | Markedly reduced |
| Outdoors, overcast, in shade | A few metres |
| Outdoors, full sun | Almost nothing |
A pale matt surface sends back more than dark concrete or a wet wall: at the same distance, the result differs by a factor of two.
How does the detector get round the problem?
The detector is not looking for light: it is looking for light that flickers at a set frequency. The laser level, switched to pulse mode, modulates its beam; the detector keeps only that modulation and ignores everything else, the sun included.
We no longer sell the detector on its own: it is taken in the box with the 12-line or the 16-line, where the manufacturer states a working range of 50 m, against 20 m by eye.
How do you work with a detector?
Five moves: stand the laser on a steady tripod and let it level itself, switch on pulse mode, clamp the detector to a grade rod with the clip supplied, slide the whole thing along the rod until the “on level” signal, mark, and start again at the next point.
- Set the laser on a steady tripod and let it level itself.
- Switch on pulse mode. Without it the detector picks up nothing — and that is not a fault.
- Fix the detector to a staff or a rule with the clamp supplied.
- Run the assembly along the staff until you get the “on level” signal.
- Mark it, and start again at the next point.
Pulse mode often weakens the visible line: that is normal, the energy goes into the modulation.
What to check before buying a detector?
Four points: that the laser level really has a pulse mode and that you know how to switch it on; that the manufacturer states compatibility for this exact pair; that the mount suits your rod, reinforced clamp or 1/4"-20 thread; and that the audible alarm can be adjusted.
- That the laser level really does have a pulse mode, and that you know how to switch it on.
- That the manufacturer states compatibility for that particular pair of instruments.
- That the mounting suits your staff: reinforced clamp, 1/4"-20 thread.
- That the audible alarm is adjustable: outdoors in noise, the display alone is not enough.
And if you work in shade?
A north-facing elevation, an overcast morning, an interior under construction with no windows fitted: the line can stay readable over ten metres or so. The detector then stays optional. But the light changes through the day, and a job that starts in shade rarely ends in shade.
The mounts that hold the instrument outdoors are in the accessories section, and the choice of instrument itself is in this guide.
- The line disappears outdoors for want of contrast, not through any fault of the instrument.
- The power is capped by the standard: it cannot be raised.
- The detector picks up a modulation, not a glow.
- With pulse mode switched off, it picks up nothing.