What Is a Spirit Level?
A spirit level serves as a fundamental tool for measuring the horizontality or verticality of a surface relative to the ground.
Beyond its primary horizontal and vertical measurements, it can also accurately gauge angles such as 45 degrees. Alternately referred to as a bubble level or simply a level, its most prevalent form is the bubble spirit level, utilizing a liquid and an air bubble within a tube. Widely employed in civil engineering, construction, surveying, and general construction tasks, it facilitates the establishment of both horizontal and vertical planes.
Applications of Spirit Levels
Spirit levels are extensively used in various fields such as civil engineering, construction, and surveying.
- Construction works
- Civil engineering projects
- Plumbing and electrical installations
- Interior finishing
- DIY and home improvement
Spirit levels are sometimes integrated into devices and equipment that require horizontal or vertical alignment. Bubble levels or circular levels are commonly embedded in such machines, which include:
- General surveying instruments (poles, rods, distance-measuring prisms, etc.), pile drivers
- Mobile cranes, aerial work platforms, satellite relay vehicles, and other vehicles
- Scales
- Workbenches
- Projectors, cameras, tripods
- Directional compasses
- Sports equipment
Principle of Spirit Levels
1. Overview of Bubble Spirit Levels
Predominantly, the bubble spirit level is the most utilized variant, with its measuring capability contingent upon the mounting angle of the bubble tube. Comprising a transparent sealed container filled with a clear liquid such as alcohol, the tube houses a single air bubble. It features reference lines (or marks), and the bubble’s position between these lines indicates the surface’s horizontal or vertical alignment.
A single spirit level may have various bubble tube configurations, such as:
- Two tubes for horizontal and vertical measurements
- Three tubes, adding a 45-degree angle measurement
- Five tubes, including 30-degree, 45-degree, and 60-degree tubes (mainly for civil engineering)
- Models with an adjustable slant function for roofing work
- Circular spirit levels, or disc levels, adhere to the same operating principle, featuring a transparent disc containing a liquid and a solitary bubble, facilitating two-dimensional leveling.
2. Gradient Measurement
The reference lines on a bubble spirit level can also facilitate gradient measurements. A four-line level (two lines on each side) can measure a 1/100 gradient (1 cm slope per 1 m), with alignment indicated when the bubble’s edge aligns with the second line from the inside. Six-line levels (three lines on each side) accommodate both 1/100 and 2/100 gradients.
3. Sensitivity and Accuracy
The sensitivity and accuracy of spirit levels are defined by JIS standards. Sensitivity is the gradient at which the bubble starts moving and is classified as:
- Type 1: 0.02mm/m
- Type 2: 0.05mm/m
- Type 3: 0.1mm/m
Accuracy refers to the error when the bubble position changes upon reversing the level. It’s expressed in height (in μm) per 1m base or in angles (in seconds). There are Class A and Class B accuracies, with Class A being more precise, but Class B is sufficient for general use.
Types of Spirit Levels
1. Overview
In addition to bubble spirit levels and circular levels, the market encompasses laser levels, angle-measuring levels (inclinometers), and digital levels.
2. Bubble and Circular Levels
In various configurations concerning the number and angles of the bubble tubes, bubble spirit levels cater to diverse requirements. Models equipped with magnets are conducive to attachment to metallic objects for determining levelness. Circular levels, while adept at measuring horizontal planes in two dimensions, typically exhibit lower accuracy than bubble levels.
Traditional bubble tubes often have black markings, which can overlap with the scale on the other side of the tube, making it difficult to read. Models with white markings make the scale on the far side less prominent, improving visibility even when scales overlap. Sizes and shapes (flat, square, etc.) also vary, allowing selection based on the application.
3. Laser Levels
Laser levels integrate laser functionality into traditional spirit levels or solely feature laser capabilities. They project laser beams onto distant surfaces such as floors or walls to ascertain levelness, supplementing surface level measurement. Point and line laser projections are available.
4. Digital Levels
Digital levels digitally display angles, offering heightened accuracy compared to traditional bubble levels. Powered by batteries, opting for models equipped with dust and waterproof features is advisable for outdoor applications.