In the use of steel tape measure, the main reasons for the error are as follows
Time:
26 Apr,2023
Standard steel tape measure The main reasons for the error in the use of steel tape measure are as follows:
1. The error of temperature change
General steel tape measure thermal expansion coefficient of α = 1.25x10-5, for each meter per degree temperature change of only one in eighty thousand, but the same steel tape measure in the temperature difference between the environment or will produce a large length change, affecting the measurement results. The error of temperature variation has been considered in the equation of ruler length.
Standard steel tape measure
3.Tension error
The size of the tensile force will affect the length of the steel tape measure, in the measurement if you do not use the spring to weigh the tensile force, will produce errors. Steel modulus of elasticity E = 2X106 KG/CM2, according to Hooke's law, 30 meters of ruler length in ± 5 kg tension error will produce ± 1.8 mm of length error.
3. The error of steel tape not horizontal
Measure the horizontal distance when the steel tape measure should try to keep horizontal, otherwise it will produce the error of distance growth. For 30 meters of the length of the ruler, the difference in height between the two ends of the ruler up to 0.4 meters will produce an error of about 2.6 mm, the relative error of 1 / 11200.
Main Rights
A measuring device comprising: a measuring tool having an end hook; and a magnetic tool which is embedded in the end hook.
1. Direct reading method
Measurement of the steel tape measure zero scale aligned with the measurement starting point, apply appropriate tension (pull the ruler force to the steel tape measure identified tension or ruler on the calibrated tension, measured by a spring scale), directly read the measurement termination point corresponding to the scale on the ruler.
2. Indirect reading method in some parts of the steel tape measure can not be used directly, you can use the steel ruler or right angle ruler, so that the zero scale is aligned with the measurement point, the ruler body and measurement direction; with the steel tape measure to the steel ruler or right angle ruler on a whole scale of the distance, the remaining length of the reading method to measure out.
3. Steel tape measure several errors in the measurement
More accurate steel tape measure factory and after a period of use must be certified and indicate the temperature, tension and length of the test. The length marked on the ruler for the nominal length, the difference between its length and the actual length is called the ruler length correction Δl, the ruler will be subject to different tension will make the ruler length change. To avoid this change, require the use of steel tape measure in accordance with the ruler on the marked tension for
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