Measuring Tapes

Measuring tapes are essential tools in various fields, from construction and woodworking to sewing and surveying. Their accuracy is categorized into different classes, mainly Class I and Class II, according to standards defined by organizations such as the European Committee for Standardization (CEN).

Permitted tolerances for measuring tapes by length according to Directive 2004/22/EC, Annex MI - 008 (also Directive 73/362/EEC)

Materials and Applications:

• Metal (steel) measuring tapes: Stand out for their durability and resistance to stretching. They are often used in construction and surveying and are available in both Class I and Class II.
• Fiberglass measuring tapes: They are lighter and corrosion-resistant, which makes them suitable for outdoor use and technical work. However, they are more prone to deformation compared to steel tapes.
• Plastic or fabric measuring tapes: Used mainly in sewing and for measuring curved or soft materials, due to their flexibility.

How to choose the right measuring tape:

When choosing a measuring tape, consider the following:

• Required accuracy: For tasks that require high accuracy, such as woodworking details or metal constructions, choose Class I. For general use, Class II is sufficient.
• Durability: For harsh environments, choose steel measuring tapes. For lighter work or where there is a risk of corrosion, fiberglass measuring tapes are suitable.
• Length and readability: Make sure the length covers your usual needs and that the graduations are clear and easy to read.

Accuracy classes:

• Class I: Measuring tapes in this class offer the highest level of accuracy. For example, at a length of 10 meters, a Class I measuring tape has a maximum permissible error of ±1,1 mm. This accuracy is critical for tasks that require absolute detail.
• Class II: Slightly less accurate than Class I measuring tapes, Class II measuring tapes have a permissible error of ±2,3 mm at 10 meters. They are the most common and are used in general construction and DIY work, where extreme accuracy is not required

Linear expansion

Measuring tapes are subject to linear expansion in the event of temperature fluctuations. If high accuracy is required, length corrections must be made. The tolerance and error limits apply for a reference temperature of 20° C.

The change in length ΔL can be calculated as follows: ΔL = L x ΔT x α

• L = Length at the measurement point
• ΔT = Deviation of the actual temperature from the reference temperature
• α = Coefficient of linear expansion

The coefficient of linear expansion α is:

• For carbon steel tape: 0,0117 mm per degree Celsius
• For stainless steel tape: 0,016 mm per degree Celsius
• For fiberglass tape: 0,005 mm per degree Celsius

Calculation example for a carbon steel tape with length 20 m and ambient temperature 30°C:

ΔL = 20 x 10 x 0,0117ΔL = 2,34 mm

The tape expands by 2,34 mm, i.e., the measured length must be corrected by -2,34 mm.

Temperature compensation table for a carbon steel measuring tape