Spirit levels are classified as precision measuring instruments and are subject to strict packaging requirements. Each spirit level must be housed in a shock-resistant case made of foam material; prior to casing, the instrument should be coated with rust-preventive oil and enclosed in a plastic bag. The shock-resistant case is then placed inside a sturdy cardboard or wooden crate, the exterior of which must be marked with the prescribed identification symbols. Spirit levels should be stored in a dry, well-ventilated warehouse free from corrosive gases. During handling and transport, strict precautions must be taken to prevent dropping, impact, or exposure to rain.
A spirit level is an angular measuring instrument used to determine the angle of deviation from a true horizontal plane. The critical component of the spirit level-the main bubble tube-features a polished inner surface; its outer surface is marked with a graduated scale, while the interior is filled with a liquid and a single air bubble. The main bubble tube is equipped with a bubble chamber designed to regulate the length of the air bubble. Although the bubble tube is typically aligned parallel to the instrument's base, this alignment may shift during use; consequently, adjustment screws are provided to correct such deviations.
Prior to taking measurements, the measuring surface of the workpiece must be thoroughly cleaned and dried. Additionally, the measuring surface should be inspected for any defects, such as scratches, rust, or burrs.
Verify that the zero-point calibration is accurate. If the calibration is incorrect, adjustable-type spirit levels must be recalibrated according to the following procedure: Place the spirit level on a flat surface plate and record the reading on the bubble tube scale. Then, at the exact same location on the surface plate, rotate the spirit level 180 degrees horizontally and record the new reading on the bubble tube scale. If the two readings are identical, the base of the spirit level is parallel to the bubble tube; if the readings differ, use the provided adjustment pin to engage the adjustment port and perform the necessary vertical adjustments.
During measurement, every effort should be made to minimize the influence of temperature fluctuations. Since the liquid within the bubble tube is highly sensitive to temperature changes, care must be taken to avoid factors that could affect the instrument, such as heat from one's hands, direct sunlight, or exhaled breath.
When taking readings, one should position oneself directly perpendicular to the bubble tube to minimize the impact of parallax errors on the measurement results.
