The specification of laser plummet (FG-LL30+ Series) stated that its accuracy is 5 mm at 100 m. Anyone knows what factors have been considered for this accuracy? I wonder if this accuracy means the refraction effect acting on the laser beam.
i doubt it is refraction; that's a very small effect especially at 100 meters. id have to check the equation, though.
I doubt refraction has much effect on a vertical beam unless you are in a situation with air at a different temperature than a vertical wall.
I have not used a laser plummet, but I do have two Zenith/Nadir plummets, both rotatable. If the laser plumet can be rotated 360, then that should take out any collimation error. What I do is rotate 90 degrees at a time, mark it, and then take the intersection of the lines across
The 5 mm may be due to the diameter of the laser spot.
John has it for approach. How they write the specs is beyond me.
For as much as that laser dances around you end up with a pretty tight result. I have been told that shutting off ventilation to the shaft will decrease the distortion of the laser.
My old boss designed real clever brackets for mounting at the top of shaft consisted of two frames, one for mounting the laser and a second to act as a fender separate from the first so that the man basket would not bump the laser bracket.
Isn't this simply the manufacturer's claim of how well the plummet's leveling system works and of the perpendicularity between the leveling system and the axis of the laser, given the limitations of the design, the tolerances of manufacturing, and what's achievable with routine maintenance and calibration? In other words, don't count on this plummet's beam being closer to vertical than 10 arcseconds (5mm @ 100m).
