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Posted by bbelly on August 20, 2006, 10:06 pm
tonyg wrote:
> Hello, Do you use laser levels and worry about accuracy. I mean on any
> given day it could be out of calibration and your work at say 40 feet
> away is not gonna be right. I just tested mine tonite against a sight
> level and at 58 each way feet its off by almost an inch. I will be
> resetting a lot of form panels tomorrow. But I just can't see the
> value in keeping a tool that could be wrong any time. Other than having
> it calibrated every other month whats a fella to do? tonyg
>
And you know the sight (dumpy) level is more accurate because ... ?
The more meaningful check is to simply gauge it against itself. I was
accustomed to accuracy of a 16th inch (or better) over about 300 ft.
Your manual should have a description of the process, but simply put,
set the unit at one end of a range, mark grade on a post at each end
(one next to you, one at the far end)
Reset with the unit turned 180. Don't even think of tryin to keep the
unit on either of the previous grades ... I'd move the tripod around to
ensure a bit of a difference in elevation. But do those same marks again.
Compare the distance of each pair of marks, and you have the error. (
Actually, you find double the error, as this shows the difference as ½
above true level, and ½ below true grade.
It seemed logical to me to repeat this test at each quadrant. I recall
at some point discovering some sort of 'conical' error, where the whole
unit was casting with a slight cone shape ... so shallow that it was of
no consequence to our work, again in the order of a sixteenth at 300 ft.
I knew how to fix one unit ... never ever touched those screws ... good
enough is better than out of service.
Brian Belliveau
retired concrete contractor
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