In the production of construction and land surveying, the most necessary tool is a measuring one. The most common was metal roulette. This tool is a housing with a winding mechanism. In the case there is a metal tape with a marked marking.
Characteristics of metal roulette
Measuring metal roulettes consist of a flat tape. In the manufacture of tape cold-rolled carbon or stainless steel is used. The use of these particular steel grades is due to the fact that the tape scale should provide constant measurement values. If a different steel grade is used in the manufacture of the tape, then errors may occur during use due to the deformation of the tape. The steel grade designation is located on the roulette case. Stainless steel is marked with the letter "H", carbon steel - with the letter "U".
Nominal lengths of manufactured metal roulettes vary from 1 m to 100 m, in increments of 1 m. The tape measure should ensure measurement accuracy in the temperature range from -40 ° C to + 50 ° C with a relative air humidity of 98%.
The resource of a standard metal roulette with stainless steel tapes is 2000 cycles, with carbon steel tapes - 1500 cycles. The concept of the cycle includes stretching the tape to the full length, tension, counting, winding the tape.
Roulette scales consist of millimeter, centimeter and meter intervals. The beginning of the scale should coincide with the end of the metal tape. If the tape measure consists of a tape longer than 10 m or more, the beginning of the scale should be removed from the end by at least 100 mm.
Preparation for checking the accuracy of metal tape measure
Verification of the accuracy of measurements of metal roulettes is carried out in accordance with the document "Methodological instructions. State system for ensuring the uniformity of measurements. Model tapes and metal measuring roulettes. Verification method. MI 1780-87" (approved by VNIIM named after DI Mendeleev 28.09.1987).
To verify the accuracy of measurements, a wall optical-mechanical comparator, an exemplary measuring tape and a magnifier with a tenfold increase are used. The comparator is a horizontal table with a length of at least 24 m, with special devices for fixing the ends of metal strips.
During the inspection, the following conditions must be met: ambient temperature within + 20 ° C, relative humidity from 60%, but not more than 80%. Checked metal tape measure, mounted on a table, must be maintained before verification begins for 15 minutes. Before starting the measurement, the tape measure should be washed with gasoline and wiped with a soft cloth.
