Stabila is a common name in the production of spirit levels and most trades probably own or have owned at least one. But what is the measuring accuracy of Stabila spirit levels?
We take a look at what a spirit level is, what it does and the manufacture of Stabila levels. We examine how the different features contribute to the overall accuracy of the level.
What Is A Bubble Level?
A tradesman has to take multiple measurements a day and for this he needs a tool that can provide him with accurate readings. One of the best ways to do this is with a bubble level, which is far more accurate than tape measures and cheaper than electronic measuring tools.
So what is a bubble level? Basically, this is an instrument that allows you to tell whether a surface, either horizontal or vertical, is level. Many trades need to work with levels including carpenters, bricklayers, plumbers and metalworkers.
Levels have acrylic glass tubes which have constant internal diameters and are incompletely filled with ethanol and a colorant for ease of reading. Not filling the tubes completely leaves a bubble which acts as the indicator.
Alcohols are used in place of water as they have lower viscosity and surface tension. It also allows the level to be used in colder temperatures where water may freeze and break the glass tubes.
The tubes have a slight upward curve in the center which is the highest point and allows the bubble to naturally rest at this point. With slight inclination in either direction the bubble will move away from the marked center line.
Most levels have more than one viewing point allowing them to be read from either side, or even upside down. But a level is only as good as its accuracy. So how accurate is a Stabila level?
Accuracy of a spirit level depends on its sensitivity. This is measured by the change of gradient or angle required to move the bubble by unit distance.
Most levels have graduated divisions on the vial housing and the sensitivity is the gradient that moves the bubble by one of these divisions. Different levels have different sensitivity.
For example on a surveyor’s level the bubble will move 2 mm for every 0.005 degrees that the vial is tilted. Stabila levels have been manufactured to the highest standards and are very accurate.
The vial is built into a block holder in the level, something that Stabila developed, along with shock-absorbing end caps. This vial block holder ensures that the vial is protected from stresses and is completely immovable.
This is achieved by corrosion-free reference rings, which helps to provide precise readings. It is inserted into the aluminum profile in a way that prohibits any movement. The vial and the profile are forever aligned with each other, thus ensuring accuracy.
This is no vain boast and Stabila offers a lifetime accuracy guarantee on their levels. For most of their products Stabila guarantees a plus or minus 0.5 mm per meter accuracy.
On their telescopic levels such as the Type 106 T the accuracy in the normal retracted position is +/- 0.5 mm/meter but in the reverse retracted position it is +/- 0.75 mm/meter.
Having guaranteed accuracy is a huge plus for Stabila, but you also need good visibility. If you can’t properly see the measurement then it won’t matter how accurate the level is. This is why high visibility is important.
The vial in a Stabila level is made of top quality and shatterproof acrylic glass. This is easy to clean so even after a trip to a muddy construction site you will be able to wipe it down. The internal liquid is a type of ethanol and is dyed to make reading easier.
Exterior surfaces on the vial are made as flat as possible to stop light from refracting onto the vial when you are trying to read it. The interior of the vial is ground with precision and the reference rings are flush with the level surface.
All of this careful and precise construction ensures that the bubble can move unhindered thus guaranteeing the accuracy of the level. Stabila levels are extremely temperature resistant to between -4 F to 122 F.
The size of the bubble and the ring spacings are designed to ensure optimum readability. Most of the levels have three viewing points which allow ease of reading from either side and also above the level. The accuracy of the top read vial is 1/32 inches over 72 inches.
A Stabila level can be used in the normal and reverse positions and for this it must be able to display the measurement with precision in either. To achieve this level of accuracy Stabila have made the walls of the upper and lower part of the vial mirror images of each other.
In this way the bubble can move unrestricted in either position and thereby provide accurate measurements. Stabila are able to produce this high degree of accuracy in their levels through precision machining in the manufacturing process.
They also engage in multi stage testing of all their products. In the normal position of the level the accuracy is 0.5 mm/meter for all aluminum spirit levels.
For models which are designed to be used in the reverse position the accuracy is 0.5 mm/meter, 0.75 mm/meter or 1.0 mm/meter.
Stabila have created many different types of level for various uses and trades. Therefore not all levels are the same. There are R beam levels, heavy-duty levels, magnetic levels and extendable levels.
One thing that all of them have in common however is that they all have to have a completely smooth measuring surface. On some levels however, not all sides can be used as a measuring surface.
For example, a mason’s level is built with two trowel ‘strike zones’ so that it can be tapped into a level position. There is a center positioned vial so that the measurement is easily readable and the correct level attained.
Most Stabila levels will have bodies that are powder-coated, anodized or painted. In some cases the measuring surface is milled flat after it has been coated.
Additional Features To Ensure Accuracy
End caps made from impact resistant plastic are fitted to many Stabila levels to protect the reliability of the measuring surface. For metalworkers, levels with rare earth magnets hold the instrument in place to provide accurate and consistent measurements.
Rare earth magnets are five times stronger than ferrite magnets. Other Stabila levels have finger grip openings to provide an easier to align level. Another version has two such finger grip openings with profiled lining for a firm grip to ensure accuracy.
Not only this, but the Stabila spirit level is covered in an electrostatic powder coating, making it easy to clean.
As we have seen, Stabila put a lot of thought and work into making their levels as accurate as possible. From the manufacture of the vial holding block down to the precision machining of the interior diameters of the vial they pay attention to the smallest detail.
They believe so strongly in the quality of their product that they offer a lifetime accuracy guarantee on their levels. Stabila understands that a spirit level is one of the fundamental tools of many tradesmen, and they want to offer the most accurate.