Re: Anti cant devices?
LFOD,
It would take several pages to get into specifics of precise levels. The link I gave should give anyone a glimpse of what is entailed.
The sensitivity of a level is defined as the change of angle or gradient required to move the bubble by a set distance (usually 2mm). If the vial has graduated divisions then the sensitivity refers to the angle or gradient change required to move the bubble by one of these divisions (often spaced at 2mm).
The sensitivity can be defined as an angle or a gradient.
As an angle, the standard units are degrees(°), minutes(') and seconds(“). 1 degree = 60 minutes and 1minute = 60seconds. (1° = 60' and 1' = 60").
As a gradient the standard units are mm/m (millimetres per metre), although sometimes inches/10 inches or a simple number gradient is used. For example a gradient of 1mm/m is the same as 0.01"/10 inches which is the same as 1:1000.
For all spirit levels the sensitivity specification is determined by the sensitivity of the vials that are used. The sensitivity is determined by the radius of curvature of the vials which the bubble moves across. Even though it cannot always be seen, all spirit level vials are curved. The principal of operation is that the bubble will move to the highest point of the radius as gravity acts on the liquid inside the vial.
The sensitivity is directly related to the radius of curvature of the vial; the longer the radius, the more sensitive the vial will be; the shorter the radius, the coarser the vial will be.
In order to determine which sensitivity is best for a particular application, it is first necessary to decide how level the product needs to be. Another way of looking at this is to consider what is the maximum angle off-level that the product will still work correctly.
Let’s say for this example that the product needs to be level within 0.1° (or 6’). The next assumption we need to make is how accurately the user can centre the bubble between the divisions on the vial. We would normally assume that this is possible to within 0.5mm although in some applications it may be more or less than this. Based on these figures, we need a vial that will give at least 0.5mm bubble movement for a 0.1° (6’) change in angle. This corresponds to 0.4° (24’) for a 2mm bubble movement, so we would say that we need a vial with a sensitivity of 24minutes per 2mm bubble movement.
Electronic or laser have a larger problem with calibration, even if you spend upwards to $400 for a unit. There are electronic digital water levels but even with those if the electronics get off they are another "return to factory" calibration problem.